java菜鸟教程学习（完整版）

java实例
一.Java 字符串
1.Java 实例 – 字符串比较
2.Java 实例 - 查找字符串最后一次出现的位置
3.Java 实例 - 删除字符串中的一个字符
4.Java 实例 - 字符串替换
5.Java 实例 - 字符串反转
6.Java 实例 - 字符串查找
7.Java 实例 - 字符串分割
8.Java 实例 - 字符串分割(StringTokenizer)
9.Java 实例 - 字符串小写转大写
10.Java 实例 - 测试两个字符串区域是否相等
11.Java 实例 - 字符串性能比较测试
12.Java 实例 - 字符串优化
13.Java 实例 - 字符串格式化
14.Java 实例 - 连接字符串
二.Java 数组
1.Java 实例 – 数组排序及元素查找
2.Java 实例 – 数组添加元素
3.Java 实例 – 获取数组长度
4.Java 实例 – 数组反转
5.Java 实例 – 数组输出
6.Java 实例 – 数组获取最大和最小值
7.Java 实例 – 数组合并
8.Java 实例 – 数组填充
9.Java 实例 – 数组扩容
10.Java 实例 – 查找数组中的重复元素
11.Java 实例 – 删除数组元素
12.Java 实例 – 数组差集
13.Java 实例 – 数组交集
14.Java 实例 – 在数组中查找指定元素
15.Java 实例 – 判断数组是否相等
16.Java 实例 - 数组并集
三.Java 时间处理
1.Java 实例 - 格式化时间（SimpleDateFormat）
2.Java 实例 - 获取当前时间
3.Java 实例 - 获取年份、月份等
4.Java 实例 - 时间戳转换成时间
四.Java 方法
1.Java 实例 – 方法重载
2.Java 实例 – 输出数组元素
3.Java 实例 – 汉诺塔算法
4.Java 实例 – 斐波那契数列
5.Java 实例 – 阶乘
6.Java 实例 – 方法覆盖
7.Java 实例 – instanceOf 关键字用法
8.Java 实例 – break 关键字用法
9.Java 实例 – continue 关键字用法
10.Java 实例 – 标签(Label)
11.Java 实例 – enum 和 switch 语句使用
12.Java 实例 – Enum（枚举）构造函数及方法的使用
13.Java 实例 – for 和 foreach循环使用
14.Java 实例 – Varargs 可变参数使用
15.Java 实例 – 重载(overloading)方法中使用 Varargs
五.打印图形
1.Java 实例 – 打印菱形
2.Java 实例 – 九九乘法表
3.Java 实例 – 打印三角形
4.Java 实例 – 打印倒立的三角形
5.Java 实例 – 打印平行四边形
6.Java 实例 – 打印矩形
六.Java 文件操作
1.Java 实例 - 文件写入
2.Java 实例 - 读取文件内容
3.Java 实例 - 删除文件
4.Java 实例 - 将文件内容复制到另一个文件
5.Java 实例 - 向文件中追加数据
6.Java 实例 - 创建临时文件
7.Java 实例 - 修改文件最后的修改日期
8.Java 实例 - 获取文件大小
9.Java 实例 - 文件重命名
10.Java 实例 - 设置文件只读
11.Java 实例 - 检测文件是否存在
12.Java 实例 - 在指定目录中创建文件
13.Java 实例 - 获取文件修改时间
14.Java 实例 - 创建文件
15.Java 实例 - 文件路径比较
七.Java 目录操作
1.Java 实例 - 递归创建目录
2.Java 实例 - 删除目录
3.Java 实例 - 判断目录是否为空
4.Java 实例 - 判断文件是否隐藏
5.Java 实例 - 获取目录大小
6.Java 实例 - 在指定目录中查找文件
7.Java 实例 - 获取文件的上级目录
8.Java 实例 - 获取目录最后修改时间
9.Java 实例 - 打印目录结构
10.Java 实例 - 遍历指定目录下的所有目录
11.Java 实例 - 遍历指定目录下的所有文件
12.Java 实例 - 在指定目录中查找文件
13.Java 实例 - 遍历系统根目录
14.Java 实例 - 查看当前工作目录
15.Java 实例 - 遍历目录
八.Java 异常处理
1.Java 实例 - 异常处理方法
2.Java 实例 - 多个异常处理（多个catch）
3.Java 实例 - Finally的用法
4.Java 实例 - 使用 catch 处理异常
5.Java 实例 - 多线程异常处理
6.Java 实例 - 获取异常的堆栈信息
7.Java 实例 - 重载方法异常处理
8.Java 实例 - 链试异常
9.Java 实例 - 自定义异常
九.Java 数据结构
1.Java 实例 – 数字求和运算
2.Java 实例 – 利用堆栈将中缀表达式转换成后缀
3.Java 实例 – 在链表（LinkedList）的开头和结尾
4.Java 实例 – 获取链表（LinkedList）的第一个
5.Java 实例 – 删除链表中的元素
6.Java 实例 – 获取链表的元素
7.Java 实例 – 获取向量元素的索引值
8.Java 实例 – 栈的实现
9.Java 实例 – 链表元素查找
10.Java 实例 – 压栈出栈的方法实现字符串反转
11.Java 实例 – 队列（Queue）用法
12.Java 实例 – 获取向量的最大元素
13.Java 实例 – 链表修改
14.Java 实例 – 旋转向量
十.Java 集合
1.Java 实例 – 数组转集合
2.Java 实例 – 集合比较
3.Java 实例 – HashMap遍历
4.Java 实例 – 集合长度
5.Java 实例 – 集合打乱顺序
6.Java 实例 – 集合遍历
7.Java 实例 – 集合反转
8.Java 实例 – 删除集合中指定元素
9.Java 实例 – 只读集合
10.Java 实例 – 集合输出
11.Java 实例 – 集合转数组
12.Java 实例 – List 循环移动元素
13.Java 实例 – 查找 List 中的最大最小值
14.Java 实例 – 遍历 HashTable 的键值
15.Java 实例 – 使用 Enumeration 遍历 HashTable
16.Java 实例 – 集合中添加不同类型元素
17.Java 实例 – List 元素替换
18.Java 实例 – List 截取
十一.Java 网络实例
1.Java 实例 – 获取指定主机的IP地址
2.Java 实例 – 查看端口是否已使用
3.Java 实例 – 获取本机ip地址及主机名
4.Java 实例 – 获取远程文件大小
5.Java 实例 – Socket 实现多线程服务器程序
6.Java 实例 – 查看主机指定文件的最后修改时间
7.Java 实例 – 使用 Socket 连接到指定主机
8.Java 实例 – 网页抓取
9.Java 实例 – 获取 URL响应头的日期信息
10.Java 实例 – 获取 URL 响应头信息
11.Java 实例 – 解析 URL
12.Java 实例 – ServerSocket 和 Socket 通信实例
十二.Java 线程
1.Java 实例 – 查看线程是否存活
2.Java 实例 – 获取当前线程名称
3.Java 实例 – 状态监测
4.Java 实例 – 线程优先级设置
5.Java 实例 – 死锁及解决方法
6.Java 实例 – 获取线程id
7.Java 实例 – 线程挂起
8.Java 实例 – 终止线程
9.Java 实例 – 生产者/消费者问题
10.Java 实例 – 获取线程状态
11.Java 实例 – 获取所有线程
12.Java 实例 – 查看线程优先级
13.Java 实例 – 中断线程
一.Java 字符串
1.Java 实例 – 字符串比较
public class StringCompareEmp{
public static void main(String args[]){

  String str = "Hello World";
  String anotherString = "hello world";
  Object objStr = str;

  System.out.println( str.compareTo(anotherString) );
  System.out.println( str.compareToIgnoreCase(anotherString) );  //忽略大小写
  System.out.println( str.compareTo(objStr.toString()));

}
}

2.Java 实例 - 查找字符串最后一次出现的位置
public class SearchlastString {
public static void main(String[] args) {

  String strOrig = "Hello world ,Hello Runoob";
  int lastIndex = strOrig.lastIndexOf("Runoob");
  if(lastIndex == - 1){
     System.out.println("没有找到字符串 Runoob");
  }else{
     System.out.println("Runoob 字符串最后出现的位置： "+ lastIndex);
  }

}
}

3.Java 实例 - 删除字符串中的一个字符
public class Main {
public static void main(String args[]) {

  String str = "this is Java";
  System.out.println(removeCharAt(str, 3));

}
public static String removeCharAt(String s, int pos) {

  return s.substring(0, pos) + s.substring(pos + 1);

}
}

4.Java 实例 - 字符串替换
public class StringReplaceEmp{
public static void main(String args[]){

  String str="Hello World";
  System.out.println( str.replace( 'H','W' ) );
  System.out.println( str.replaceFirst("He", "Wa") );
  System.out.println( str.replaceAll("He", "Ha") );

}
}

5.Java 实例 - 字符串反转
public class StringReverseExample{
public static void main(String[] args){

  String string="runoob";
  String reverse = new StringBuffer(string).reverse().toString();
  System.out.println("字符串反转前:"+string);
  System.out.println("字符串反转后:"+reverse);

}
}

6.Java 实例 - 字符串查找
public class SearchStringEmp {
public static void main(String[] args) {

  String strOrig = "Google Runoob Taobao";
  int intIndex = strOrig.indexOf("Runoob");
  if(intIndex == - 1){
     System.out.println("没有找到字符串 Runoob");
  }else{
     System.out.println("Runoob 字符串位置 " + intIndex);
  }

}
}

7.Java 实例 - 字符串分割
public class JavaStringSplitEmp {
public static void main(String args[]){

  
  String str = "www-runoob-com";
  String[] temp;
  String delimeter = "-";  // 指定分割字符
  temp = str.split(delimeter); // 分割字符串
  // 普通 for 循环
  for(int i =0; i < temp.length ; i++){
     System.out.println(temp[i]);
     System.out.println("");
  }

  System.out.println("------java for each循环输出的方法-----");
  String str1 = "www.runoob.com";
  String[] temp1;
  String delimeter1 = "\\.";  // 指定分割字符， . 号需要转义
  temp1 = str1.split(delimeter1); // 分割字符串
  for(String x :  temp1){
     System.out.println(x);
     System.out.println("");
  }

}
}

8.Java 实例 - 字符串分割(StringTokenizer)
import java.util.StringTokenizer;

public class Main {

public static void main(String[] args) {

    String str = "This is String , split by StringTokenizer, created by runoob";
    StringTokenizer st = new StringTokenizer(str);

    System.out.println("----- 通过空格分隔 ------");
    while (st.hasMoreElements()) {
        System.out.println(st.nextElement());
    }

    System.out.println("----- 通过逗号分隔 ------");
    StringTokenizer st2 = new StringTokenizer(str, ",");

    while (st2.hasMoreElements()) {
        System.out.println(st2.nextElement());
    }
}

}

9.Java 实例 - 字符串小写转大写
public class StringToUpperCaseEmp {

public static void main(String[] args) {
    String str = "string runoob";
    String strUpper = str.toUpperCase();
    System.out.println("原始字符串: " + str);
    System.out.println("转换为大写: " + strUpper);
}

}

10.Java 实例 - 测试两个字符串区域是否相等
public class StringRegionMatch{
public static void main(String[] args){

  String first_str = "Welcome to Microsoft";
  String second_str = "I work with microsoft";
  boolean match1 = first_str.
  regionMatches(11, second_str, 12, 9);
  boolean match2 = first_str.
  regionMatches(true, 11, second_str, 12, 9); //第一个参数 true 表示忽略大小写区别
  System.out.println("区分大小写返回值：" + match1);
  System.out.println("不区分大小写返回值：" + match2);

}
}

11.Java 实例 - 字符串性能比较测试
public class StringComparePerformance{
public static void main(String[] args){

  long startTime = System.currentTimeMillis();
  for(int i=0;i<50000;i++){
     String s1 = "hello";
     String s2 = "hello"; 
  }
  long endTime = System.currentTimeMillis();
  System.out.println("通过 String 关键词创建字符串" 
  + " : "+ (endTime - startTime) 
  + " 毫秒" );       
  long startTime1 = System.currentTimeMillis();
  for(int i=0;i<50000;i++){
     String s3 = new String("hello");
     String s4 = new String("hello");
  }
  long endTime1 = System.currentTimeMillis();
  System.out.println("通过 String 对象创建字符串" 
  + " : " + (endTime1 - startTime1)
  + " 毫秒");

}
}

12.Java 实例 - 字符串优化
public class StringOptimization {

public static void main(String[] args){
    String variables[] = new String[50000];      
    for( int i=0;i <50000;i++){
        variables[i] = "s"+i;
    }
    long startTime0 = System.currentTimeMillis();
    for(int i=0;i<50000;i++){
        variables[i] = "hello";
    }
    long endTime0 = System.currentTimeMillis();
    System.out.println("直接使用字符串： "+ (endTime0 - startTime0)  + " ms" );
    long startTime1 = System.currentTimeMillis();
        for(int i=0;i<50000;i++){
        variables[i] = new String("hello");
    }
    long endTime1 = System.currentTimeMillis();
    System.out.println("使用 new 关键字：" + (endTime1 - startTime1) + " ms");
    long startTime2 = System.currentTimeMillis();
    for(int i=0;i<50000;i++){
        variables[i] = new String("hello");
        variables[i] = variables[i].intern();          
    }
    long endTime2 = System.currentTimeMillis();
    System.out.println("使用字符串对象的 intern() 方法: " 
    + (endTime2 - startTime2)
    + " ms");
}

}

13.Java 实例 - 字符串格式化
import java.util.*;

public class StringFormat {

public static void main(String[] args){
    double e = Math.E;
    System.out.format("%f%n", e);
    System.out.format(Locale.CHINA  , "%-10.4f%n%n", e);  //指定本地为中国（CHINA）
}

}

14.Java 实例 - 连接字符串
public class StringConcatenate {

public static void main(String[] args){
    long startTime = System.currentTimeMillis();
    for(int i=0;i<5000;i++){
        String result = "This is"
        + "testing the"
        + "difference"+ "between"
        + "String"+ "and"+ "StringBuffer";
    }
    long endTime = System.currentTimeMillis();
    System.out.println("字符串连接" 
    + " - 使用 + 操作符 : " 
    + (endTime - startTime)+ " ms");
    long startTime1 = System.currentTimeMillis();
    for(int i=0;i<5000;i++){
        StringBuffer result = new StringBuffer();
        result.append("This is");
        result.append("testing the");
        result.append("difference");
        result.append("between");
        result.append("String");
        result.append("and");
        result.append("StringBuffer");
    }
    long endTime1 = System.currentTimeMillis();
    System.out.println("字符串连接" 
    + " - 使用 StringBuffer : "
    + (endTime1 - startTime1)+ " ms");
}

}

二.Java 数组
1.Java 实例 – 数组排序及元素查找
import java.util.Arrays;

public class MainClass {

public static void main(String args[]) throws Exception {
    int array[] = { 2, 5, -2, 6, -3, 8, 0, -7, -9, 4 };
    Arrays.sort(array);
    printArray("数组排序结果为", array);
    int index = Arrays.binarySearch(array, 2);
    System.out.println("元素 2  在第 " + index + " 个位置");
}
private static void printArray(String message, int array[]) {
    System.out.println(message
    + ": [length: " + array.length + "]");
    for (int i = 0; i < array.length; i++) {
        if(i != 0){
            System.out.print(", ");
        }
        System.out.print(array[i]);
    }
    System.out.println();
}

}

2.Java 实例 – 数组添加元素
import java.util.Arrays;

public class MainClass {
public static void main(String args[]) throws Exception {

  int array[] = { 2, 5, -2, 6, -3, 8, 0, -7, -9, 4 };
  Arrays.sort(array);
  printArray("数组排序", array);
  int index = Arrays.binarySearch(array, 1);
  System.out.println("元素 1 所在位置（负数为不存在）："
  + index);  
  int newIndex = -index - 1;
  array = insertElement(array, 1, newIndex);
  printArray("数组添加元素 1", array);

}
private static void printArray(String message, int array[]) {

  System.out.println(message
  + ": [length: " + array.length + "]");
  for (int i = 0; i < array.length; i++) {
     if (i != 0){
        System.out.print(", ");
     }
     System.out.print(array[i]);         
  }
  System.out.println();

}
private static int[] insertElement(int original[],
int element, int index) {

  int length = original.length;
  int destination[] = new int[length + 1];
  System.arraycopy(original, 0, destination, 0, index);
  destination[index] = element;
  System.arraycopy(original, index, destination, index
  + 1, length - index);
  return destination;

}
}

3.Java 实例 – 获取数组长度
public class Main {
public static void main(String args[]) {

  String[][] data = new String[2][5];
  System.out.println("第一维数组长度: " + data.length);
  System.out.println("第二维数组长度: " + data[0].length);

}
}

4.Java 实例 – 数组反转
public class RunoobTest {

/* 反转数组*/
static void reverse(int a[], int n) 
{ 
    int[] b = new int[n]; 
    int j = n; 
    for (int i = 0; i < n; i++) { 
        b[j - 1] = a[i]; 
        j = j - 1; 
    } 

    /*输入反转数组*/
    System.out.println("反转后数组是: \n"); 
    for (int k = 0; k < n; k++) { 
        System.out.println(b[k]); 
    } 
} 

public static void main(String[] args) 
{ 
    int [] arr = {10, 20, 30, 40, 50}; 
    reverse(arr, arr.length); 
}

}

5.Java 实例 – 数组输出
public class Welcome {

public static void main(String[] args){
    String[] runoobs = new String[3];
    runoobs[0] = "菜鸟教程";
    runoobs[1] = "菜鸟工具";
    runoobs[2] = "菜鸟笔记";
    for (int i = 0; i < runoobs.length; i++){
        System.out.println(runoobs[i]);
    }
}

}

6.Java 实例 – 数组获取最大和最小值
import java.util.Arrays;
import java.util.Collections;

public class Main {

public static void main(String[] args) {
    Integer[] numbers = { 8, 2, 7, 1, 4, 9, 5};
    int min = (int) Collections.min(Arrays.asList(numbers));
    int max = (int) Collections.max(Arrays.asList(numbers));
    System.out.println("最小值: " + min);
    System.out.println("最大值: " + max);
}

}

7.Java 实例 – 数组合并
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main {

public static void main(String args[]) {
    String a[] = { "A", "E", "I" };
    String b[] = { "O", "U" };
    List list = new ArrayList(Arrays.asList(a));
    list.addAll(Arrays.asList(b));
    Object[] c = list.toArray();
    System.out.println(Arrays.toString(c));
}

}

8.Java 实例 – 数组填充
import java.util.*;

public class FillTest {

public static void main(String args[]) {
    int array[] = new int[6];
    Arrays.fill(array, 100);
    for (int i=0, n=array.length; i < n; i++) {
        System.out.println(array[i]);
    }
    System.out.println();
    Arrays.fill(array, 3, 6, 50);
    for (int i=0, n=array.length; i< n; i++) {
        System.out.println(array[i]);
    }
}

}

9.Java 实例 – 数组扩容
public class Main {

public static void main(String[] args) {
    String[] names = new String[] { "A", "B", "C" };
    String[] extended = new String[5];
    extended[3] = "D";
    extended[4] = "E";
    System.arraycopy(names, 0, extended, 0, names.length);
    for (String str : extended){
        System.out.println(str);
    }
}

}

10.Java 实例 – 查找数组中的重复元素
public class MainClass {

public static void main(String[] args) 
{
    int[] my_array = {1, 2, 5, 5, 6, 6, 7, 2, 9, 2};
    findDupicateInArray(my_array);

}

public static void findDupicateInArray(int[] a) {
    int count=0;
    for(int j=0;j<a.length;j++) {
        for(int k =j+1;k<a.length;k++) {
            if(a[j]==a[k]) {
                count++;
            }
        }
        if(count==1)
           System.out.println( "重复元素 : " +  a[j] );
        count = 0;
    }
}

}

11.Java 实例 – 删除数组元素
import java.util.Arrays;

public class RunoobTest {

public static void main(String[] args) {
    int[] oldarray = new int[] {3, 4, 5, 6, 7};// 原始数组
    int num = 2;   // 删除索引为 2 的元素，即删除第三个元素 5
    int[] newArray = new int[oldarray.length-1];// 新数组，长度为原始数组减去 1
    
    for(int i=0;i<newArray.length; i++) {
        // 判断元素是否越界
        if (num < 0 || num >= oldarray.length) {
            throw new RuntimeException("元素越界... "); 
        } 
        // 
        if(i<num) {
            newArray[i] = oldarray[i];
        }
        else {
            newArray[i] = oldarray[i+1];
        }
    }
    // 打印输出数组内容
    System.out.println(Arrays.toString(oldarray));
    oldarray = newArray;
    System.out.println(Arrays.toString(oldarray));
}

}

12.Java 实例 – 数组差集
import java.util.ArrayList;

public class Main {

public static void main(String[] args)  {
    ArrayList objArray = new ArrayList();
    ArrayList objArray2 = new ArrayList();
    objArray2.add(0,"common1");
    objArray2.add(1,"common2");
    objArray2.add(2,"notcommon");
    objArray2.add(3,"notcommon1");
    objArray.add(0,"common1");
    objArray.add(1,"common2");
    objArray.add(2,"notcommon2");
    System.out.println("array1 的元素" +objArray);
    System.out.println("array2 的元素" +objArray2);
    objArray.removeAll(objArray2);
    System.out.println("array1 与 array2 数组差集为："+objArray);
}

}

13.Java 实例 – 数组交集
import java.util.ArrayList;

public class Main {

public static void main(String[] args)  {
    ArrayList objArray = new ArrayList();
    ArrayList objArray2 = new ArrayList();
    objArray2.add(0,"common1");
    objArray2.add(1,"common2");
    objArray2.add(2,"notcommon");
    objArray2.add(3,"notcommon1");
    objArray.add(0,"common1");
    objArray.add(1,"common2");
    objArray.add(2,"notcommon2");
    System.out.println("array1 数组元素："+objArray);
    System.out.println("array2 数组元素："+objArray2);
    objArray.retainAll(objArray2);
    System.out.println("array2 & array1 数组交集为："+objArray);
}

}

14.Java 实例 – 在数组中查找指定元素
import java.util.ArrayList;

public class Main {

public static void main(String[] args)  {
    ArrayList<String> objArray = new ArrayList<String>();
    ArrayList<String> objArray2 = new ArrayList<String>();
    objArray2.add(0,"common1");
    objArray2.add(1,"common2");
    objArray2.add(2,"notcommon");
    objArray2.add(3,"notcommon1");
    objArray.add(0,"common1");
    objArray.add(1,"common2");
    System.out.println("objArray 的数组元素："+objArray);
    System.out.println("objArray2 的数组元素："+objArray2);
    System.out.println("objArray 是否包含字符串common2? ： "
    +objArray.contains("common2"));
    System.out.println("objArray2 是否包含数组 objArray? ："
    +objArray2.contains(objArray) );
}

}

15.Java 实例 – 判断数组是否相等
import java.util.Arrays;

public class Main {

public static void main(String[] args) throws Exception {
    int[] ary = {1,2,3,4,5,6};
    int[] ary1 = {1,2,3,4,5,6};
    int[] ary2 = {1,2,3,4};
    System.out.println("数组 ary 是否与数组 ary1相等? ："
    +Arrays.equals(ary, ary1));
    System.out.println("数组 ary 是否与数组 ary2相等? ："
    +Arrays.equals(ary, ary2));
}

}

16.Java 实例 - 数组并集
import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

public class Main {

public static void main(String[] args) throws Exception {
    String[] arr1 = { "1", "2", "3" };
    String[] arr2 = { "4", "5", "6" };
    String[] result_union = union(arr1, arr2);
    System.out.println("并集的结果如下：");

    for (String str : result_union) {
        System.out.println(str);
    }
}

// 求两个字符串数组的并集，利用set的元素唯一性
public static String[] union(String[] arr1, String[] arr2) {
    Set<String> set = new HashSet<String>();

    for (String str : arr1) {
        set.add(str);
    }

    for (String str : arr2) {
        set.add(str);
    }

    String[] result = {  };

    return set.toArray(result);
}

}

三.Java 时间处理
1.Java 实例 - 格式化时间（SimpleDateFormat）
import java.text.SimpleDateFormat;
import java.util.Date;

public class Main{

public static void main(String[] args){
    Date date = new Date();
    String strDateFormat = "yyyy-MM-dd HH:mm:ss";
    SimpleDateFormat sdf = new SimpleDateFormat(strDateFormat);
    System.out.println(sdf.format(date));
}

}

2.Java 实例 - 获取当前时间
import java.text.SimpleDateFormat;
import java.util.Date;

public class Main{

public static void main(String[] args){
    
    SimpleDateFormat sdf = new SimpleDateFormat();// 格式化时间 
    sdf.applyPattern("yyyy-MM-dd HH:mm:ss a");// a为am/pm的标记  
    Date date = new Date();// 获取当前时间 
    System.out.println("现在时间：" + sdf.format(date)); // 输出已经格式化的现在时间（24小时制） 
}

}

3.Java 实例 - 获取年份、月份等
import java.util.Calendar;

public class Main {

public static void main(String[] args) {
    Calendar cal = Calendar.getInstance();
    int day = cal.get(Calendar.DATE);
    int month = cal.get(Calendar.MONTH) + 1;
    int year = cal.get(Calendar.YEAR);
    int dow = cal.get(Calendar.DAY_OF_WEEK);
    int dom = cal.get(Calendar.DAY_OF_MONTH);
    int doy = cal.get(Calendar.DAY_OF_YEAR);

    System.out.println("当期时间: " + cal.getTime());
    System.out.println("日期: " + day);
    System.out.println("月份: " + month);
    System.out.println("年份: " + year);
    System.out.println("一周的第几天: " + dow);  // 星期日为一周的第一天输出为 1，星期一输出为 2，以此类推
    System.out.println("一月中的第几天: " + dom);
    System.out.println("一年的第几天: " + doy);
}

}

4.Java 实例 - 时间戳转换成时间
import java.text.SimpleDateFormat;
import java.util.Date;

public class Main{

public static void main(String[] args){
    Long timeStamp = System.currentTimeMillis();  //获取当前时间戳
    SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
    String sd = sdf.format(new Date(Long.parseLong(String.valueOf(timeStamp))));      // 时间戳转换成时间
    System.out.println("格式化结果：" + sd);

    SimpleDateFormat sdf2 = new SimpleDateFormat("yyyy 年 MM 月 dd 日 HH 时 mm 分 ss 秒");
    String sd2 = sdf2.format(new Date(Long.parseLong(String.valueOf(timeStamp))));
    System.out.println("格式化结果：" + sd2);

}
}

四.Java 方法
1.Java 实例 – 方法重载
class MyClass {

int height;
MyClass() {
    System.out.println("无参数构造函数");
    height = 4;
}
MyClass(int i) {
    System.out.println("房子高度为 " + i + " 米");
    height = i;
}
void info() {
    System.out.println("房子高度为 " + height + " 米");
}
void info(String s) {
    System.out.println(s + ": 房子高度为 " + height + " 米");
}

}
public class MainClass {

public static void main(String[] args) {
    MyClass t = new MyClass(3);
    t.info();
    t.info("重载方法");
    //重载构造函数
    new MyClass();
}

}

2.Java 实例 – 输出数组元素
public class MainClass {

public static void printArray(Integer[] inputArray) {
    for (Integer element : inputArray){
        System.out.printf("%s ", element);
        System.out.println();
    }
}
public static void printArray(Double[] inputArray) {
    for (Double element : inputArray){
        System.out.printf("%s ", element);
        System.out.println();
    }
}
public static void printArray(Character[] inputArray) {
    for (Character element : inputArray){
        System.out.printf("%s ", element);
        System.out.println();
    }
}
public static void main(String args[]) {
    Integer[] integerArray = { 1, 2, 3, 4, 5, 6 };
    Double[] doubleArray = { 1.1, 2.2, 3.3, 4.4, 5.5, 6.6, 7.7 };
    Character[] characterArray = { 'H', 'E', 'L', 'L', 'O' };
    System.out.println("输出整型数组:");
    printArray(integerArray);
    System.out.println("\n输出双精度型数组:");
    printArray(doubleArray);
    System.out.println("\n输出字符型数组:");
    printArray(characterArray);
}

}

3.Java 实例 – 汉诺塔算法
public class MainClass {

public static void main(String[] args) {
    int nDisks = 3;
    doTowers(nDisks, 'A', 'B', 'C');
}
public static void doTowers(int topN, char from, char inter, char to) {
    if (topN == 1){
        System.out.println("Disk 1 from "
        + from + " to " + to);
    }else {
        doTowers(topN - 1, from, to, inter);
        System.out.println("Disk "
        + topN + " from " + from + " to " + to);
        doTowers(topN - 1, inter, from, to);
    }
}

}

4.Java 实例 – 斐波那契数列
public class MainClass {

public static void main(String[] args) {
    for (int counter = 0; counter <= 10; counter++){
        System.out.printf("Fibonacci of %d is: %d\n", counter, fibonacci(counter));
    }
}

public static long fibonacci(long number) {
    if ((number == 0) || (number == 1))
        return number;
    else
        return fibonacci(number - 1) + fibonacci(number - 2);
}

}

5.Java 实例 – 阶乘
public class MainClass {

public static void main(String args[]) {
for (int counter = 0; counter <= 10; counter++){
    System.out.printf("%d! = %d\n", counter,
    factorial(counter));
}
}
public static long factorial(long number) {
    if (number <= 1)
        return 1;
    else
        return number * factorial(number - 1);
}

}

6.Java 实例 – 方法覆盖
public class Findareas{

public static void main (String []agrs){
    Figure f= new Figure(10 , 10);
    Rectangle r= new Rectangle(9 , 5);
    Figure figref;
    figref=f;
    System.out.println("Area is :"+figref.area());
    figref=r;
    System.out.println("Area is :"+figref.area());
}

}
class Figure{

double dim1;
double dim2;
Figure(double a , double b) {
    dim1=a;
    dim2=b;
}
Double area() {
    System.out.println("Inside area for figure.");
    return(dim1*dim2);
}

}
class Rectangle extends Figure {

Rectangle(double a, double b) {
    super(a ,b);
}
Double area() {
    System.out.println("Inside area for rectangle.");
    return(dim1*dim2);
}

}

7.Java 实例 – instanceOf 关键字用法
/*
author by runoob.com
Main.java
*/
import java.util.ArrayList;
import java.util.Vector;

public class Main {

public static void main(String[] args) {
Object testObject = new ArrayList();

  displayObjectClass(testObject);

}
public static void displayObjectClass(Object o) {

  if (o instanceof Vector)
  System.out.println("对象是 java.util.Vector 类的实例");
  else if (o instanceof ArrayList)
  System.out.println("对象是 java.util.ArrayList 类的实例");
  else
  System.out.println("对象是 " + o.getClass() + " 类的实例");

}
}

8.Java 实例 – break 关键字用法
public class Main {

public static void main(String[] args) {
    int[] intary = { 99,12,22,34,45,67,5678,8990 };
    int no = 5678;
    int i = 0;
    boolean found = false;
    for ( ; i < intary.length; i++) {
        if (intary[i] == no) {
            found = true;
            break;
        }
    }
    if (found) {
        System.out.println(no + " 元素的索引位置在: " + i);
    } 
    else {
        System.out.println(no + " 元素不在数组中");
    }
}

}

9.Java 实例 – continue 关键字用法
public class Main {

public static void main(String[] args) {
    StringBuffer searchstr = new StringBuffer("hello how are you. ");
    int length = searchstr.length();
    int count = 0;
    for (int i = 0; i < length; i++) {
        if (searchstr.charAt(i) != 'h')
        continue;
        count++;
        searchstr.setCharAt(i, 'h');
    }
    System.out.println("发现 " + count 
    + " 个 h 字符");
    System.out.println(searchstr);
}

}

10.Java 实例 – 标签(Label)
public class Main {

public static void main(String[] args) {
    outerLoop:
    for (int i = 0; i < 3; i++) {
        innerLoop:
        for (int j = 0; j < 3; j++) {
            if (i == 1 && j == 1) {
                break outerLoop; // 跳出外部循环
            }
            System.out.println("i: " + i + ", j: " + j);
        }
    }
}

}

11.Java 实例 – enum 和 switch 语句使用
enum Car {

lamborghini,tata,audi,fiat,honda

}
public class Main {

public static void main(String args[]){
    Car c;
    c = Car.tata;
    switch(c) {
        case lamborghini:
            System.out.println("你选择了 lamborghini!");
            break;
        case tata:
            System.out.println("你选择了 tata!");
            break;
        case audi:
            System.out.println("你选择了 audi!");
            break;
        case fiat:
            System.out.println("你选择了 fiat!");
            break;
        case honda:
            System.out.println("你选择了 honda!");
            break;
        default:
            System.out.println("我不知道你的车型。");
            break;
    }
}

}

12.Java 实例 – Enum（枚举）构造函数及方法的使用
enum Car {

lamborghini(900),tata(2),audi(50),fiat(15),honda(12);
private int price;
Car(int p) {
    price = p;
}
int getPrice() {
    return price;
}

}
public class Main {

public static void main(String args[]){
    System.out.println("所有汽车的价格：");
    for (Car c : Car.values())
    System.out.println(c + " 需要 " 
    + c.getPrice() + " 千美元。");
}

}

13.Java 实例 – for 和 foreach循环使用
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Main
{

public static void main(String[] args)
{
    int[] arr = {1, 2, 3, 4, 5};
    
    System.out.println("----------使用 for 循环------------");
    for(int i=0; i<arr.length; i++)
    {
        System.out.println(arr[i]);
    }
    
    System.out.println("---------使用 For-Each 循环-------------");
    
    //增强的 for 循环 For-Each
    for(int element:arr)
    {
        System.out.println(element);
    }
    
    System.out.println("---------For-Each 循环二维数组-------------");
    
    //遍历二维数组
    int[][] arr2 = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}} ;
    for(int[] row : arr2)
    {
        for(int element : row)
        {
            System.out.println(element);
        }
    }
    
    //以三种方式遍历集合 List
    List<String> list = new ArrayList<String>();
    
    list.add("Google");
    list.add("Runoob");
    list.add("Taobao");
    
    System.out.println("----------方式1：普通for循环-----------");
    for(int i = 0; i < list.size(); i++)
    {
        System.out.println(list.get(i));
    }
    
    System.out.println("----------方式2：使用迭代器-----------");
    for(Iterator<String> iter = list.iterator(); iter.hasNext();)
    {
        System.out.println(iter.next());
    }
    
    System.out.println("----------方式3：For-Each 循环-----------");
    for(String str: list)
    {
        System.out.println(str);
    }
}

}

14.Java 实例 – Varargs 可变参数使用
public class Main {

static int  sumvarargs(int... intArrays){
    int sum, i;
    sum=0;
    for(i=0; i< intArrays.length; i++) {
        sum += intArrays[i];
    }
    return(sum);
}
public static void main(String args[]){
    int sum=0;
    sum = sumvarargs(new int[]{10,12,33});
    System.out.println("数字相加之和为: " + sum);
}

}

15.Java 实例 – 重载(overloading)方法中使用 Varargs
public class Main {

static void vaTest(int ... no) {
    System.out.print("vaTest(int ...): " 
    + "参数个数: " + no.length +" 内容: ");
    for(int n : no)
    System.out.print(n + " ");
    System.out.println();
}
static void vaTest(boolean ... bl) {
    System.out.print("vaTest(boolean ...) " +
    "参数个数: " + bl.length + " 内容: ");
    for(boolean b : bl)
    System.out.print(b + " ");
    System.out.println();
}
static void vaTest(String msg, int ... no) {
    System.out.print("vaTest(String, int ...): " +
    msg +"参数个数: "+ no.length +" 内容: ");
    for(int  n : no)
    System.out.print(n + " ");
    System.out.println();
}
public static void main(String args[]){
    vaTest(1, 2, 3);
    vaTest("测试: ", 10, 20);
    vaTest(true, false, false);
}

}

五.打印图形
1.Java 实例 – 打印菱形
public class Diamond {

public static void main(String[] args) {
    print(8); // 输出 8 行的菱形
}

public static void print(int size) {
    if (size % 2 == 0) {
        size++; // 计算菱形大小
    }
    for (int i = 0; i < size / 2 + 1; i++) {
        for (int j = size / 2 + 1; j > i + 1; j--) {
            System.out.print(" "); // 输出左上角位置的空白
        }
        for (int j = 0; j < 2 * i + 1; j++) {
            System.out.print("*"); // 输出菱形上半部边缘
        }
        System.out.println(); // 换行
    }
    for (int i = size / 2 + 1; i < size; i++) {
        for (int j = 0; j < i - size / 2; j++) {
            System.out.print(" "); // 输出菱形左下角空白
        }
        for (int j = 0; j < 2 * size - 1 - 2 * i; j++) {
            System.out.print("*"); // 输出菱形下半部边缘
        }
        System.out.println(); // 换行
    }
}

}

2.Java 实例 – 九九乘法表
public class MultiplicationTable {

public static void main(String[] args) {
    for(int i=1;i<=9;i++) {
        for(int j=1;j<=i;j++) {
            System.out.print(j+"×"+i+"="+i*j+"\t");// \t 跳到下一个TAB位置
        }
        System.out.println();
    }
}

}

3.Java 实例 – 打印三角形
class Demo{

public static void main(String[] args){
    for(int i=1;i<=5;i++){
        for(int j=5; i<=j; j--)
            System.out.print(" ");
        for(int j=1; j<=i; j++)
            System.out.print("*");
        for(int j=1; j<i; j++)
            System.out.print("*");
        System.out.println();
    }
}

}

4.Java 实例 – 打印倒立的三角形
public class InvertedTriangle {

public static void main(String[] args) {
     //打印倒立的三角形
    for (int m = 1; m <= 4; m++) {
        //打印空格
        for (int n = 0; n <= m; n++) {
            System.out.print(" ");
        }
        //打印*
        for (int x = 1; x <= 7 -2 * (m - 1); x++) {
            System.out.print("*");
        }
        System.out.println();
    }        
}

}

5.Java 实例 – 打印平行四边形
public class Parallelogram {

public static void main(String[] args) {
     //外层循环 每次打出一个*
    for (int i = 1; i <=5; i++) {
        //填充空格
        for (int j = 1; j <= 5 - i; j++) {
            System.out.print(" ");
        }
        //内层循环 每次打印一个*
        for (int k = 1; k <= 5; k++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

}

6.Java 实例 – 打印矩形
public class Rect {

public static void main(String[] args) {
     //外层循环 每次输出一行*
    for (int i = 1; i <= 5; i++) {
        System.out.print("*");
        //内层循环 每次输出一个*
        for (int j = 1; j <= 5; j++) {
            System.out.print("*");
        }
        System.out.println();
    }
}

}

六.Java 文件操作
1.Java 实例 - 文件写入
/*
author by runoob.com
Main.java
*/

import java.io.*;

public class Main {

public static void main(String[] args)  {
    try {
        BufferedWriter out = new BufferedWriter(new FileWriter("runoob.txt"));
        out.write("菜鸟教程");
        out.close();
        System.out.println("文件创建成功！");
    } catch (IOException e) {
    }
}

}

2.Java 实例 - 读取文件内容
import java.io.*;

public class Main {

public static void main(String[] args)  {
    try {
        BufferedReader in = new BufferedReader(new FileReader("test.log"));
        String str;
        while ((str = in.readLine()) != null) {
            System.out.println(str);
        }
        System.out.println(str);
    } catch (IOException e) {
    }
}

}

3.Java 实例 - 删除文件
import java.io.*;

public class Main
{

public static void main(String[] args)
{
    try{
        File file = new File("c:\\test.txt");
        if(file.delete()){
            System.out.println(file.getName() + " 文件已被删除！");
        }else{
            System.out.println("文件删除失败！");
        }
    }catch(Exception e){
        e.printStackTrace();
    }
}

}

4.Java 实例 - 将文件内容复制到另一个文件
import java.io.*;

public class Main {

public static void main(String[] args) throws Exception {
    BufferedWriter out1 = new BufferedWriter(new FileWriter("srcfile"));
    out1.write("string to be copied\n");
    out1.close();
    InputStream in = new FileInputStream(new File("srcfile"));
    OutputStream out = new FileOutputStream
    (new File("destnfile"));
    byte[] buf = new byte[1024];
    int len;
    while ((len = in.read(buf)) > 0) {
        out.write(buf, 0, len);
    }
    in.close();
    out.close();
    BufferedReader in1 = new BufferedReader(new FileReader("destnfile"));
    String str;
    while ((str = in1.readLine()) != null) {
        System.out.println(str);
    }
    in1.close();
}

}

5.Java 实例 - 向文件中追加数据
import java.io.*;

public class Main {

public static void main(String[] args) throws Exception {
    try {
        BufferedWriter out = new BufferedWriter(new FileWriter("filename"));
        out.write("aString1\n");
        out.close();
        out = new BufferedWriter(new FileWriter("filename",true));
        out.write("aString2");
        out.close();
        BufferedReader in = new BufferedReader(new FileReader("filename"));
        String str;
        while ((str = in.readLine()) != null) {
            System.out.println(str);
        }
        in.close();
    }
        catch (IOException e) {
        System.out.println("exception occoured"+ e);
    }
}

}

6.Java 实例 - 创建临时文件
import java.io.*;

public class Main {

public static void main(String[] args) throws Exception {
    File temp = File.createTempFile("testrunoobtmp", ".txt");
    System.out.println("文件路径: "+temp.getAbsolutePath());
    temp.deleteOnExit();
    BufferedWriter out = new BufferedWriter(new FileWriter(temp));
    out.write("aString");
    System.out.println("临时文件已创建:");
    out.close();
}

}

7.Java 实例 - 修改文件最后的修改日期
import java.io.File;
import java.util.Date;

public class Main {

public static void main(String[] args) throws Exception {
    File fileToChange = new File("C:/myjavafile.txt");
    fileToChange.createNewFile();
    Date filetime = new Date(fileToChange.lastModified());
    System.out.println(filetime.toString());
    System.out.println(fileToChange.setLastModified(System.currentTimeMillis()));
    filetime = new Date(fileToChange.lastModified());
    System.out.println(filetime.toString());
}

}

8.Java 实例 - 获取文件大小
import java.io.File;

public class Main {

public static long getFileSize(String filename) {
    File file = new File(filename);
    if (!file.exists() || !file.isFile()) {
        System.out.println("文件不存在");
        return -1;
    }
    return file.length();
}
public static void main(String[] args) {
    long size = getFileSize("c:/java.txt");
    System.out.println("java.txt文件大小为: " + size);
}

}

9.Java 实例 - 文件重命名
import java.io.File;
import java.io.IOException;

public class RunoobTest {

public static void main(String[] args) throws IOException {
    // 旧的文件或目录
    File oldName = new File("./runoob-test.txt");
    // 新的文件或目录
    File newName = new File("./runoob-test-2.txt");
    if (newName.exists()) {  //  确保新的文件名不存在
        throw new java.io.IOException("file exists");
    }
    if(oldName.renameTo(newName)) {
        System.out.println("已重命名");
    } else {
        System.out.println("Error");
    }
}

}

10.Java 实例 - 设置文件只读
import java.io.File;

public class Main {

public static void main(String[] args) {
    File file = new File("C:/java.txt");
    System.out.println(file.setReadOnly());
    System.out.println(file.canWrite());
}

}

11.Java 实例 - 检测文件是否存在
import java.io.File;

public class Main {

public static void main(String[] args) {
    File file = new File("C:/java.txt");
    System.out.println(file.exists());
}

}

12.Java 实例 - 在指定目录中创建文件
import java.io.File;

public class Main {

public static void main(String[] args) throws Exception {
    File file = null;
    File dir = new File("C:/");
    file = File.createTempFile
    ("JavaTemp", ".javatemp", dir);
    System.out.println(file.getPath());
}

}

13.Java 实例 - 获取文件修改时间
import java.io.File;
import java.util.Date;

public class Main {

public static void main(String[] args) {
    File file = new File("Main.java");
    Long lastModified = file.lastModified();
    Date date = new Date(lastModified);
    System.out.println(date);
}

}

14.Java 实例 - 创建文件
import java.io.File;
import java.io.IOException;

public class Main {

public static void main(String[] args) {
    try{
        File file = new File("C:/myfile.txt");
        if(file.createNewFile())
            System.out.println("文件创建成功！");
        else
            System.out.println("出错了，该文件已经存在。");
    }
    catch(IOException ioe) {
        ioe.printStackTrace();
    }
}

}

15.Java 实例 - 文件路径比较
import java.io.File;

public class Main {

public static void main(String[] args) {
    File file1 = new File("C:/File/demo1.txt");
    File file2 = new File("C:/java/demo1.txt");
    if(file1.compareTo(file2) == 0) {
        System.out.println("文件路径一致！");
    } else {
        System.out.println("文件路径不一致！");
    }
}

}

七.Java 目录操作
1.Java 实例 - 递归创建目录
import java.io.File;

public class Main {

public static void main(String[] args) {
    String directories = "D:\\a\\b\\c\\d\\e\\f\\g\\h\\i";
    File file = new File(directories);
    boolean result = file.mkdirs();
    System.out.println("Status = " + result);
}

}

2.Java 实例 - 删除目录
import java.io.File;

public class Main {

public static void main(String[] argv) throws Exception {
    // 删除当前目录下的 test 目录
    deleteDir(new File("./test"));
}
public static boolean deleteDir(File dir) {
    if (dir.isDirectory()) {
        String[] children = dir.list();
        for (int i = 0; i < children.length; i++) {
            boolean success = deleteDir
            (new File(dir, children[i]));
            if (!success) {
                return false;
            }
        }
    }
    if(dir.delete()) {
        System.out.println("目录已被删除！");
        return true;
    } else {
        System.out.println("目录删除失败！");
        return false;
    }
}

}

3.Java 实例 - 判断目录是否为空
import java.io.File;

public class Main
{

public static void main(String[] args)
{
    File file = new File("./testdir");  // 当前目录下的 testdir目录
    if(file.isDirectory()){
        if(file.list().length>0){
            System.out.println("目录不为空!");
        }else{
            System.out.println("目录为空!");
        }
    }else{
        System.out.println("这不是一个目录!");
    }
}

}

4.Java 实例 - 判断文件是否隐藏
import java.io.File;

public class Main {

public static void main(String[] args) {
    File file = new File("C:/Demo.txt");
    System.out.println(file.isHidden());
}

}

5.Java 实例 - 获取目录大小
import java.io.File;
import org.apache.commons.io.FileUtils;

public class Main {

public static void main(String[] args) {
    long size = FileUtils.sizeOfDirectory(new File("C:/test"));
    System.out.println("Size: " + size + " bytes");
}

}

6.Java 实例 - 在指定目录中查找文件
import java.io.File;

public class Main {

public static void main(String[] argv) throws Exception {
    File dir = new File("../java");
    String[] children = dir.list();
    if (children == null) {
        System.out.println("该目录不存在");
    }
    else {
        for (int i = 0; i < children.length; i++) {
            String filename = children[i];
            System.out.println(filename);
        }
    }
}

}

7.Java 实例 - 获取文件的上级目录
import java.io.File;

public class Main {

public static void main(String[] args) {
    File file = new File("C:/File/demo.txt");
    String strParentDirectory = file.getParent();
    System.out.println("文件的上级目录为 : " + strParentDirectory);
}

}

8.Java 实例 - 获取目录最后修改时间
import java.io.File;
import java.util.Date;

public class Main {

public static void main(String[] args) {
    File file = new File("C://FileIO//demo.txt");
    System.out.println("最后修改时间：" + new Date(file.lastModified()));
}

}

9.Java 实例 - 打印目录结构
import java.io.File;
import java.io.IOException;

public class FileUtil {

public static void main(String[] a)throws IOException{
    showDir(1, new File("d:\\Java"));
}
static void showDir(int indent, File file) throws IOException {
    for (int i = 0; i < indent; i++)
        System.out.print('-');
    System.out.println(file.getName());
    if (file.isDirectory()) {
        File[] files = file.listFiles();
        for (int i = 0; i < files.length; i++)
            showDir(indent + 4, files[i]);
    }
}

}

10.Java 实例 - 遍历指定目录下的所有目录
import java.io.*;

class Main {
public static void main(String[] args) {

  File dir = new File("F:");
  File[] files = dir.listFiles();
  FileFilter fileFilter = new FileFilter() {
     public boolean accept(File file) {
        return file.isDirectory();
     }
  };
  files = dir.listFiles(fileFilter);
  System.out.println(files.length);
  if (files.length == 0) {
     System.out.println("目录不存在或它不是一个目录");
  }
  else {
     for (int i=0; i< files.length; i++) {
        File filename = files[i];
        System.out.println(filename.toString());
     }
  }

}
}

11.Java 实例 - 遍历指定目录下的所有文件
import java.io.File;

class Main {

public static void main(String[] args) {
    File dir = new File("C:");
    String[] children = dir.list();
    if (children == null) {
        System.out.println( "目录不存在或它不是一个目录");
    }
    else {
        for (int i=0; i< children.length; i++) {
            String filename = children[i];
            System.out.println(filename);
        }
    }
}

}

12.Java 实例 - 在指定目录中查找文件
import java.io.*;

class Main {
public static void main(String[] args) {

  File dir = new File("C:");
  FilenameFilter filter = new FilenameFilter() {
     public boolean accept
     (File dir, String name) {
        return name.startsWith("b");
    }
  };
  String[] children = dir.list(filter);
  if (children == null) {
     System.out.println("目录不存在或它不是一个目录");
  } 
  else {
     for (int i=0; i < children.length; i++) {
        String filename = children[i];
        System.out.println(filename);
     }
  }

}
}

13.Java 实例 - 遍历系统根目录
import java.io.*;

class Main{

public static void main(String[] args){
    File[] roots = File.listRoots();
    System.out.println("系统所有根目录：");
    for (int i=0; i < roots.length; i++) {
        System.out.println(roots[i].toString());
    }
}

}

14.Java 实例 - 查看当前工作目录
class Main {

public static void main(String[] args) {
    String curDir = System.getProperty("user.dir");
    System.out.println("你当前的工作目录为 :" + curDir);
}

}

15.Java 实例 - 遍历目录
import java.io.File;

public class Main {

public static void main(String[] argv) throws Exception {
    System.out.println("遍历目录");
    File dir = new File("/www/java"); //要遍历的目录
    visitAllDirsAndFiles(dir);
}
public static void visitAllDirsAndFiles(File dir) {
    System.out.println(dir);
    if (dir.isDirectory()) {
        String[] children = dir.list();
        for (int i = 0; i < children.length; i++) {
            visitAllDirsAndFiles(new File(dir, children[i]));
        }
    }
}

}

八.Java 异常处理
1.Java 实例 - 异常处理方法
class ExceptionDemo
{

public static void main(String[] args) {
    try {
        throw new Exception("My Exception");
    } catch (Exception e) {
        System.err.println("Caught Exception");
        System.err.println("getMessage():" + e.getMessage());
        System.err.println("getLocalizedMessage():" + e.getLocalizedMessage());
        System.err.println("toString():" + e);
        System.err.println("printStackTrace():");
        e.printStackTrace();
    }
}

}

2.Java 实例 - 多个异常处理（多个catch）
class Demo
{

int div(int a,int b) throws ArithmeticException,ArrayIndexOutOfBoundsException//在功能上通过throws的关键字声明该功能可能出现问题  
{  
    int []arr = new int [a];  

    System.out.println(arr[4]);//制造的第一处异常  

    return a/b;//制造的第二处异常  
}

}

class ExceptionDemo
{

public static void main(String[]args) //throws Exception  
{  
    Demo d = new Demo();  

    try  
        {  
            int x = d.div(4,0);//程序运行截图中的三组示例 分别对应此处的三行代码  
            //int x = d.div(5,0);  
            //int x = d.div(4,1);  
            System.out.println("x="+x);   
    }  
    catch (ArithmeticException e)  
    {  
        System.out.println(e.toString());  
    }  
    catch (ArrayIndexOutOfBoundsException e)  
    {  
        System.out.println(e.toString());  
    }  
    catch (Exception e)//父类 写在此处是为了捕捉其他没预料到的异常 只能写在子类异常的代码后面  
                        //不过一般情况下是不写的   
    {  
        System.out.println(e.toString());  
    }  
      


    System.out.println("Over");  
}

}

3.Java 实例 - Finally的用法
public class ExceptionDemo2 {
public static void main(String[] argv) {

  new ExceptionDemo2().doTheWork();

}
public void doTheWork() {

  Object o = null;
  for (int i=0; i<5; i++) {
     try {
        o = makeObj(i);
     }
     catch (IllegalArgumentException e) {
        System.err.println
        ("Error: ("+ e.getMessage()+").");
        return;   
     }
     finally {
        System.err.println("都已执行完毕");
        if (o==null)
        System.exit(0);
    }
    System.out.println(o); 
  }

}
public Object makeObj(int type)
throws IllegalArgumentException {

  if (type == 1)  
  throw new IllegalArgumentException
  ("不是指定的类型： " + type);
  return new Object();

}
}

4.Java 实例 - 使用 catch 处理异常
public class Main {

public static void main (String args[]) {
    int array[]={20,20,40};
    int num1=15,num2=10;
    int result=10;
    try{
        result = num1/num2;
        System.out.println("结果为 " +result);
        for(int i =5;i >=0; i--) {
            System.out.println ("数组的元素值为 " +array[i]);
        }
    }
    catch (Exception e) {
        System.out.println("触发异常 : "+e);
    }
}

}

5.Java 实例 - 多线程异常处理
class MyThread extends Thread{

public void run(){
    System.out.println("Throwing in " +"MyThread");
    throw new RuntimeException();
}

}
class Main {

public static void main(String[] args){
    MyThread t = new MyThread();
    t.start();
    try{
        Thread.sleep(1000);
    }
    catch (Exception x){
        System.out.println("Caught it" + x);
    }
    System.out.println("Exiting main");
}

}

6.Java 实例 - 获取异常的堆栈信息
public class Main{

public static void main (String args[]){
    int array[]={20,20,40};
    int num1=15,num2=10;
    int result=10;
    try{
        result = num1/num2;
        System.out.println("The result is" +result);
        for(int i =5; i>=0; i--) {
            System.out.println("The value of array is" +array[i]);
        }
    }
    catch (Exception e) {
        e.printStackTrace();
    }
}

}

7.Java 实例 - 重载方法异常处理
public class Main {

double method(int i) throws Exception{
    return i/0;
}
boolean method(boolean b) {
    return !b;
}
static double method(int x, double y) throws Exception  {
    return x + y ;
}
static double method(double x, double y) {
    return x + y - 3;
}   
public static void main(String[] args) {
    Main mn = new Main();
    try{
        System.out.println(method(10, 20.0));
        System.out.println(method(10.0, 20));
        System.out.println(method(10.0, 20.0));
        System.out.println(mn.method(10));
    }
    catch (Exception ex){
        System.out.println("exception occoure: "+ ex);
    }
}

}

8.Java 实例 - 链试异常
public class Main {

public static void main (String args[])throws Exception  {
    int n=20,result=0;
    try{
        result=n/0;
        System.out.println("结果为"+result);
    }
    catch(ArithmeticException ex){
        System.out.println("发算术异常: "+ex);
        try {
            throw new NumberFormatException();
        }
        catch(NumberFormatException ex1) {
            System.out.println("手动抛出链试异常 : "+ex1);
        }
    }
}

}

9.Java 实例 - 自定义异常
class WrongInputException extends Exception { // 自定义的类

WrongInputException(String s) {
    super(s);
}

}
class Input {

void method() throws WrongInputException {
    throw new WrongInputException("Wrong input"); // 抛出自定义的类
}

}
class TestInput {

public static void main(String[] args){
    try {
        new Input().method();
    }
    catch(WrongInputException wie) {
        System.out.println(wie.getMessage());
    }
}

}

九.Java 数据结构
1.Java 实例 – 数字求和运算
public class Main {

public static void main(String[] args) {
    int limit=100;
    int sum=0;
    int i=1;
    do
    {
        sum=sum+i;
        i++;
    }
    while(i<=limit);
    System.out.println("sum="+sum);
}

}

2.Java 实例 – 利用堆栈将中缀表达式转换成后缀
import java.io.IOException;

public class InToPost {
private Stack theStack;
private String input;
private String output = "";
public InToPost(String in) {

  input = in;
  int stackSize = input.length();
  theStack = new Stack(stackSize);

}
public String doTrans() {

  for (int j = 0; j < input.length(); j++) {
     char ch = input.charAt(j);
     switch (ch) {
        case '+': 
        case '-':
        gotOper(ch, 1); 
        break; 
        case '*': 
        case '/':
        gotOper(ch, 2); 
        break; 
        case '(': 
        theStack.push(ch);
        break;
        case ')': 
        gotParen(ch); 
        break;
        default: 
        output = output + ch; 
        break;
     }
  }
  while (!theStack.isEmpty()) {
     output = output + theStack.pop();
  }
  System.out.println(output);
  return output;

}
public void gotOper(char opThis, int prec1) {

  while (!theStack.isEmpty()) {
     char opTop = theStack.pop();
     if (opTop == '(') {
        theStack.push(opTop);
        break;
     }
     else {
        int prec2;
        if (opTop == '+' || opTop == '-')
        prec2 = 1;
        else
        prec2 = 2;
        if (prec2 < prec1) { 
           theStack.push(opTop);
           break;
        }
        else
        output = output + opTop;
     }
  }
  theStack.push(opThis);

}
public void gotParen(char ch){

  while (!theStack.isEmpty()) {
     char chx = theStack.pop();
     if (chx == '(') 
     break; 
     else
     output = output + chx; 
  }

}
public static void main(String[] args)
throws IOException {

  String input = "1+2*4/5-7+3/6";
  String output;
  InToPost theTrans = new InToPost(input);
  output = theTrans.doTrans(); 
  System.out.println("Postfix is " + output + '\n');

}
class Stack {

  private int maxSize;
  private char[] stackArray;
  private int top;
  public Stack(int max) {
     maxSize = max;
     stackArray = new char[maxSize];
     top = -1;
  }
  public void push(char j) {
     stackArray[++top] = j;
  }
  public char pop() {
     return stackArray[top--];
  }
  public char peek() {
     return stackArray[top];
  }
  public boolean isEmpty() {
     return (top == -1);
 }

}
}

3.Java 实例 – 在链表（LinkedList）的开头和结尾
import java.util.LinkedList;

public class Main {

public static void main(String[] args) {
    LinkedList<String> lList = new LinkedList<String>();
    lList.add("1");
    lList.add("2");
    lList.add("3");
    lList.add("4");
    lList.add("5");
    System.out.println(lList);
    lList.addFirst("0");
    System.out.println(lList);
    lList.addLast("6");
    System.out.println(lList);
}

}

4.Java 实例 – 获取链表（LinkedList）的第一个
import java.util.LinkedList;

public class Main {

public static void main(String[] args) {
    LinkedList<String> lList = new LinkedList<String>();
    lList.add("100");
    lList.add("200");
    lList.add("300");
    lList.add("400");
    lList.add("500");
    System.out.println("链表的第一个元素是：" + lList.getFirst());
    System.out.println("链表的最后一个元素是：" + lList.getLast());
}

}

5.Java 实例 – 删除链表中的元素
import java.util.*;

public class Main {
public static void main(String[] args) {

  LinkedList<String> lList = new LinkedList<String>();
  lList.add("1");
  lList.add("8");
  lList.add("6");
  lList.add("4");
  lList.add("5");
  System.out.println(lList);
  lList.subList(2, 4).clear();
  System.out.println(lList);

}
}

6.Java 实例 – 获取链表的元素
import java.util.*;

public class Main {
private LinkedList list = new LinkedList();
public void push(Object v) {

  list.addFirst(v);

}
public Object top() {

  return list.getFirst();

}
public Object pop() {

  return list.removeFirst();

}
public static void main(String[] args) {

  Main stack = new Main();
  for (int i = 30; i < 40; i++)
     stack.push(new Integer(i));
  System.out.println(stack.top());
  System.out.println(stack.pop());
  System.out.println(stack.pop());
  System.out.println(stack.pop());

}
}

7.Java 实例 – 获取向量元素的索引值
import java.util.Collections;
import java.util.Vector;

public class Main {
public static void main(String[] args) {

  Vector v = new Vector();
  v.add("X");
  v.add("M");
  v.add("D");
  v.add("A");
  v.add("O");
  Collections.sort(v);
  System.out.println(v);
  int index = Collections.binarySearch(v, "D");
  System.out.println("元素索引值为 : " + index);

}
}

8.Java 实例 – 栈的实现
]`public class MyStack {
private int maxSize;
private long[] stackArray;
private int top;
public MyStack(int s) {

  maxSize = s;
  stackArray = new long[maxSize];
  top = -1;

}
public void push(long j) {

  stackArray[++top] = j;

}
public long pop() {

  return stackArray[top--];

}
public long peek() {

  return stackArray[top];

}
public boolean isEmpty() {

  return (top == -1);

}
public boolean isFull() {

  return (top == maxSize - 1);

}
public static void main(String[] args) {

  MyStack theStack = new MyStack(10); 
  theStack.push(10);
  theStack.push(20);
  theStack.push(30);
  theStack.push(40);
  theStack.push(50);
  while (!theStack.isEmpty()) {
     long value = theStack.pop();
     System.out.print(value);
     System.out.print(" ");
  }
  System.out.println("");

}
}`

9.Java 实例 – 链表元素查找
import java.util.LinkedList;

public class Main {
public static void main(String[] args) {

  LinkedList lList = new LinkedList();
  lList.add("1");
  lList.add("2");
  lList.add("3");
  lList.add("4");
  lList.add("5");
  lList.add("2");
  System.out.println("元素 2 第一次出现的位置：" + lList.indexOf("2"));
  System.out.println("元素 2 最后一次出现的位置："+ lList.lastIndexOf("2"));

}
}

10.Java 实例 – 压栈出栈的方法实现字符串反转
import java.io.IOException;

public class StringReverserThroughStack {
private String input;
private String output;
public StringReverserThroughStack(String in) {

  input = in;

}
public String doRev() {

  int stackSize = input.length(); 
  Stack theStack = new Stack(stackSize); 
  for (int i = 0; i < input.length(); i++) {
     char ch = input.charAt(i); 
     theStack.push(ch); 
  }
  output = "";
  while (!theStack.isEmpty()) {
     char ch = theStack.pop(); 
     output = output + ch; 
  }
  return output;

}
public static void main(String[] args)
throws IOException {

  String input = "www.w3cschool.cc";
  String output;
  StringReverserThroughStack theReverser = 
  new StringReverserThroughStack(input);
  output = theReverser.doRev();
  System.out.println("反转前： " + input);
  System.out.println("反转后： " + output);

}
class Stack {

  private int maxSize;
  private char[] stackArray;
  private int top;
  public Stack(int max) {
     maxSize = max;
     stackArray = new char[maxSize];
     top = -1;
  }
  public void push(char j) {
     stackArray[++top] = j;
  }
  public char pop() {
     return stackArray[top--];
  }
  public char peek() {
     return stackArray[top];
  }
  public boolean isEmpty() {
     return (top == -1);
  }

}
}

11.Java 实例 – 队列（Queue）用法
import java.util.LinkedList;
import java.util.Queue;

public class Main {

public static void main(String[] args) {
    //add()和remove()方法在失败的时候会抛出异常(不推荐)
    Queue<String> queue = new LinkedList<String>();
    //添加元素
    queue.offer("a");
    queue.offer("b");
    queue.offer("c");
    queue.offer("d");
    queue.offer("e");
    for(String q : queue){
        System.out.println(q);
    }
    System.out.println("===");
    System.out.println("poll="+queue.poll()); //返回第一个元素，并在队列中删除
    for(String q : queue){
        System.out.println(q);
    }
    System.out.println("===");
    System.out.println("element="+queue.element()); //返回第一个元素 
    for(String q : queue){
        System.out.println(q);
    }
    System.out.println("===");
    System.out.println("peek="+queue.peek()); //返回第一个元素 
    for(String q : queue){
        System.out.println(q);
    }
}

}

12.Java 实例 – 获取向量的最大元素
import java.util.Collections;
import java.util.Vector;

public class Main {
public static void main(String[] args) {

  Vector v = new Vector();
  v.add(new Double("3.4324"));
  v.add(new Double("3.3532"));
  v.add(new Double("3.342"));
  v.add(new Double("3.349"));
  v.add(new Double("2.3"));
  Object obj = Collections.max(v);
  System.out.println("最大元素是："+obj);

}
}

13.Java 实例 – 链表修改
import java.util.LinkedList;

public class Main {
public static void main(String[] a) {

  LinkedList officers = new LinkedList();
  officers.add("B");
  officers.add("B");
  officers.add("T");
  officers.add("H");
  officers.add("P");
  System.out.println(officers);
  officers.set(2, "M");
  System.out.println(officers);

}
}

14.Java 实例 – 旋转向量
import java.util.Collections;
import java.util.Vector;

public class Main {
public static void main(String[] args) {

  Vector<String> v = new Vector();
  v.add("1");
  v.add("2");
  v.add("3");
  v.add("4");
  v.add("5");
  System.out.println(v);
  Collections.swap(v, 0, 4);
  System.out.println("旋转后");
  System.out.println(v);

}
}

十.Java 集合
1.Java 实例 – 数组转集合
import java.util.*;
import java.io.*;

public class ArrayToCollection{
public static void main(String args[])
throws IOException{

  int n = 5;         // 5 个元素
  String[] name = new String[n];
  for(int i = 0; i < n; i++){
     name[i] = String.valueOf(i);
  }
  List<String> list = Arrays.asList(name); 
  System.out.println();
  for(String li: list){
     String str = li;
     System.out.print(str + " ");
  }

}
}

2.Java 实例 – 集合比较
import java.util.Collections;
import java.util.Set;
import java.util.TreeSet;

class Main {

public static void main(String[] args) {
    String[] coins = { "Penny", "nickel", "dime", "Quarter", "dollar" };
    Set<String> set = new TreeSet<String>();
    for (int i = 0; i < coins.length; i++) {
        set.add(coins[i]);
    }
    System.out.println(Collections.min(set));
    System.out.println(Collections.min(set, String.CASE_INSENSITIVE_ORDER));
    for (int i = 0; i <= 10; i++) {
        System.out.print("-");
    }
    System.out.println("");
    System.out.println(Collections.max(set));
    System.out.println(Collections.max(set, String.CASE_INSENSITIVE_ORDER));
}

}

3.Java 实例 – HashMap遍历
import java.util.*;

public class Main {
public static void main(String[] args) {

  HashMap< String, String> hMap = 
  new HashMap< String, String>();
  hMap.put("1", "1st");
  hMap.put("2", "2nd");
  hMap.put("3", "3rd");
  Collection cl = hMap.values();
  Iterator itr = cl.iterator();
  while (itr.hasNext()) {
     System.out.println(itr.next());
 }

}
}

4.Java 实例 – 集合长度
import java.util.*;

public class Main {
public static void main(String [] args) {

  System.out.println( "集合实例!\n" ); 
  int size;
  HashSet collection = new HashSet ();
  String str1 = "Yellow", str2 = "White", str3 = 
  "Green", str4 = "Blue";  
  Iterator iterator;
  collection.add(str1);    
  collection.add(str2);   
  collection.add(str3);   
  collection.add(str4);
  System.out.print("集合数据: ");  
  iterator = collection.iterator();     
  while (iterator.hasNext()){
     System.out.print(iterator.next() + " ");  
  }
  System.out.println();
  size = collection.size();
  if (collection.isEmpty()){
     System.out.println("集合是空的");
  }
  else{
     System.out.println( "集合长度: " + size);
  }
  System.out.println();

}
}

5.Java 实例 – 集合打乱顺序
import java.util.*;

public class Main {

public static void main(String[] args) {
    List<Integer> list = new ArrayList<Integer>();
    for (int i = 0; i < 10; i++)
        list.add(new Integer(i));
    System.out.println("打乱前:");
    System.out.println(list);

    for (int i = 1; i < 6; i++) {
        System.out.println("第" + i + "次打乱：");
        Collections.shuffle(list);
        System.out.println(list);
    }
}

6.Java 实例 – 集合遍历
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;

public class Main {

public static void main(String[] args) {

  // List集合的遍历
  listTest();
  // Set集合的遍历
  setTest();

}

private static void setTest() {

  Set<String> set = new HashSet<String>();
  set.add("JAVA");
  set.add("C");
  set.add("C++");
  // 重复数据添加失败
  set.add("JAVA");
  set.add("JAVASCRIPT");

  // 使用iterator遍历set集合
  Iterator<String> it = set.iterator();
  while (it.hasNext()) {
     String value = it.next();
     System.out.println(value);
  }
  
  // 使用增强for循环遍历set集合
  for(String s: set){
     System.out.println(s);
  }

}

// 遍历list集合
private static void listTest() {

  List<String> list = new ArrayList<String>();
  list.add("菜");
  list.add("鸟");
  list.add("教");
  list.add("程");
  list.add("www.runoob.com");

  // 使用iterator遍历
  Iterator<String> it = list.iterator();
  while (it.hasNext()) {
     String value = it.next();
     System.out.println(value);
  }

  // 使用传统for循环进行遍历
  for (int i = 0, size = list.size(); i < size; i++) {
     String value = list.get(i);
     System.out.println(value);
  }

  // 使用增强for循环进行遍历
  for (String value : list) {
     System.out.println(value);
  }

}
}

7.Java 实例 – 集合反转
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.ListIterator;

class Main {
public static void main(String[] args) {

  String[] coins = { "A", "B", "C", "D", "E" };
  List l = new ArrayList();
  for (int i = 0; i < coins.length; i++)
     l.add(coins[i]);
  ListIterator liter = l.listIterator();
  System.out.println("反转前");
  while (liter.hasNext())
     System.out.println(liter.next());
  Collections.reverse(l);
  liter = l.listIterator();
  System.out.println("反转后");
  while (liter.hasNext())
     System.out.println(liter.next());

}
}

8.Java 实例 – 删除集合中指定元素
import java.util.*;

public class Main {
public static void main(String [] args) {

  System.out.println( "集合实例!\n" ); 
  int size;
  HashSet collection = new HashSet ();
  String str1 = "Yellow", str2 = "White", str3 = 
  "Green", str4 = "Blue";  
  Iterator iterator;
  collection.add(str1);    
  collection.add(str2);   
  collection.add(str3);   
  collection.add(str4);
  System.out.print("集合数据: ");  
  iterator = collection.iterator();     
  while (iterator.hasNext()){
     System.out.print(iterator.next() + " ");  
  }
  System.out.println();
  collection.remove(str2);
  System.out.println("删除之后 [" + str2 + "]\n");
  System.out.print("现在集合的数据是: ");
  iterator = collection.iterator();     
  while (iterator.hasNext()){
     System.out.print(iterator.next() + " ");  
  }
  System.out.println();
  size = collection.size();
  System.out.println("集合大小: " + size + "\n");

}
}

9.Java 实例 – 只读集合
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;

public class Main {
public static void main(String[] argv)
throws Exception {

  List stuff = Arrays.asList(new String[] { "a", "b" });
  List list = new ArrayList(stuff);
  list = Collections.unmodifiableList(list);
  try {
     list.set(0, "new value");
  } 
    catch (UnsupportedOperationException e) {
  }
  Set set = new HashSet(stuff);
  set = Collections.unmodifiableSet(set);
  Map map = new HashMap();
  map = Collections.unmodifiableMap(map);
  System.out.println("集合现在是只读");

}
}

10.Java 实例 – 集合输出
import java.util.*;

public class Main{
public static void main(String[] args) {

  System.out.println("TreeMap 实例！\n");
  TreeMap tMap = new TreeMap();
  tMap.put(1, "Sunday");
  tMap.put(2, "Monday");
  tMap.put(3, "Tuesday");
  tMap.put(4, "Wednesday");
  tMap.put(5, "Thursday");
  tMap.put(6, "Friday");
  tMap.put(7, "Saturday");
  System.out.println("TreeMap 键：" 
  + tMap.keySet());
  System.out.println("TreeMap 值：" 
  + tMap.values());
  System.out.println("键为 5 的值为: " + tMap.get(5)+ "\n");
  System.out.println("第一个键: " + tMap.firstKey() 
  + " Value: " 
  + tMap.get(tMap.firstKey()) + "\n");
  System.out.println("最后一个键: " + tMap.lastKey() 
  + " Value: "+ tMap.get(tMap.lastKey()) + "\n");
  System.out.println("移除第一个数据: " 
  + tMap.remove(tMap.firstKey()));
  System.out.println("现在 TreeMap 键为: " 
  + tMap.keySet());
  System.out.println("现在 TreeMap 包含: " 
  + tMap.values() + "\n");
  System.out.println("移除最后一个数据: " 
  + tMap.remove(tMap.lastKey()));
  System.out.println("现在 TreeMap 键为: " 
  + tMap.keySet());
  System.out.println("现在 TreeMap 包含: " 
  + tMap.values());

}
}

11.Java 实例 – 集合转数组
import java.util.*;

public class Main{
public static void main(String[] args){

  List<String> list = new ArrayList<String>();
  list.add("菜"); 
  list.add("鸟"); 
  list.add("教");
  list.add("程");
  list.add("www.runoob.com");
  String[] s1 = list.toArray(new String[0]); 
  for(int i = 0; i < s1.length; ++i){
     String contents = s1[i];
     System.out.print(contents);
 }

}
}

12.Java 实例 – List 循环移动元素
import java.util.*;

public class Main {
public static void main(String[] args) {

  List list = Arrays.asList("one Two three Four five six".split(" "));
  System.out.println("List :"+list);
  Collections.rotate(list, 3);
  System.out.println("rotate: " + list);

}
}

13.Java 实例 – 查找 List 中的最大最小值
import java.util.*;

public class Main {
public static void main(String[] args) {

  List list = Arrays.asList("one Two three Four five six one three Four".split(" "));
  System.out.println(list);
  System.out.println("最大值: " + Collections.max(list));
  System.out.println("最小值: " + Collections.min(list));

}
}

14.Java 实例 – 遍历 HashTable 的键值
import java.util.Enumeration;
import java.util.Hashtable;

public class Main {
public static void main(String[] args) {

  Hashtable ht = new Hashtable();
  ht.put("1", "One");
  ht.put("2", "Two");
  ht.put("3", "Three");
  Enumeration e = ht.keys();
  while (e.hasMoreElements()){
     System.out.println(e.nextElement());
  }

}
}

15.Java 实例 – 使用 Enumeration 遍历 HashTable
import java.util.Enumeration;
import java.util.Hashtable;

public class Main {
public static void main(String[] args) {

  Hashtable ht = new Hashtable();
  ht.put("1", "One");
  ht.put("2", "Two");
  ht.put("3", "Three");
  Enumeration e = ht.elements();
  while(e.hasMoreElements()){
     System.out.println(e.nextElement());
  }

}
}

16.Java 实例 – 集合中添加不同类型元素
import java.util.Map;
import java.util.Set;
import java.util.SortedMap;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;

public class Main {
public static void main(String[] args) {

  List lnkLst = new LinkedList();
  lnkLst.add("element1");
  lnkLst.add("element2");
  lnkLst.add("element3");
  lnkLst.add("element4");
  displayAll(lnkLst);
  List aryLst = new ArrayList();
  aryLst.add("x");
  aryLst.add("y");
  aryLst.add("z");
  aryLst.add("w");
  displayAll(aryLst);
  Set hashSet = new HashSet();
  hashSet.add("set1");
  hashSet.add("set2");
  hashSet.add("set3");
  hashSet.add("set4");
  displayAll(hashSet);
  SortedSet treeSet = new TreeSet();
  treeSet.add("1");
  treeSet.add("2");
  treeSet.add("3");
  treeSet.add("4");
  displayAll(treeSet);
  LinkedHashSet lnkHashset = new LinkedHashSet();
  lnkHashset.add("one");
  lnkHashset.add("two");
  lnkHashset.add("three");
  lnkHashset.add("four");
  displayAll(lnkHashset);
  Map map1 = new HashMap();
  map1.put("key1", "J");
  map1.put("key2", "K");
  map1.put("key3", "L");
  map1.put("key4", "M");
  displayAll(map1.keySet());
  displayAll(map1.values());
  SortedMap map2 = new TreeMap();
  map2.put("key1", "JJ");
  map2.put("key2", "KK");
  map2.put("key3", "LL");
  map2.put("key4", "MM");
  displayAll(map2.keySet());
  displayAll(map2.values());
  LinkedHashMap map3 = new LinkedHashMap();
  map3.put("key1", "JJJ");
  map3.put("key2", "KKK");
  map3.put("key3", "LLL");
  map3.put("key4", "MMM");
  displayAll(map3.keySet());
  displayAll(map3.values());

}
static void displayAll(Collection col) {

  Iterator itr = col.iterator();
  while (itr.hasNext()) {
     String str = (String) itr.next();
     System.out.print(str + " ");
  }
  System.out.println();

}
}

17.Java 实例 – List 元素替换
import java.util.*;

public class Main {
public static void main(String[] args) {

  List list = Arrays.asList("one Two three Four five six one three Four".split(" "));
  System.out.println("List :"+list);
  Collections.replaceAll(list, "one", "hundrea");
  System.out.println("replaceAll: " + list);

}
}

18.Java 实例 – List 截取
import java.util.*;

public class Main {
public static void main(String[] args) {

  List list = Arrays.asList("one Two three Four five six one three Four".split(" "));
  System.out.println("List :"+list);
  List sublist = Arrays.asList("three Four".split(" "));
  System.out.println("子列表 :"+sublist);
  System.out.println("indexOfSubList: "
  + Collections.indexOfSubList(list, sublist));
  System.out.println("lastIndexOfSubList: "
  + Collections.lastIndexOfSubList(list, sublist));

}
}

十一.Java 网络实例
1.Java 实例 – 获取指定主机的IP地址
import java.net.InetAddress;
import java.net.UnknownHostException;

public class GetIP {

public static void main(String[] args) {
    InetAddress address = null;
    try {
        address = InetAddress.getByName("www.runoob.com");
    }
    catch (UnknownHostException e) {
        System.exit(2);
    }
    System.out.println(address.getHostName() + "=" + address.getHostAddress());
    System.exit(0);
}

}

2.Java 实例 – 查看端口是否已使用
import java.net.*;
import java.io.*;

public class Main {
public static void main(String[] args) {

  Socket Skt;
  String host = "localhost";
  if (args.length > 0) {
     host = args[0];
  }
  for (int i = 0; i < 1024; i++) {
     try {
        System.out.println("查看 "+ i);
        Skt = new Socket(host, i);
        System.out.println("端口 " + i + " 已被使用");
     }
     catch (UnknownHostException e) {
        System.out.println("Exception occured"+ e);
        break;
     }
     catch (IOException e) {
     }
  }

}
}

3.Java 实例 – 获取本机ip地址及主机名
import java.net.InetAddress;
import java.net.UnknownHostException;

public class NetworkInfo {

public static void main(String[] args) {
    try {
        // 获取本地主机对象
        InetAddress localHost = InetAddress.getLocalHost();
        
        // 获取主机名
        String hostName = localHost.getHostName();
        System.out.println("主机名: " + hostName);
        
        // 获取IP地址
        String hostAddress = localHost.getHostAddress();
        System.out.println("IP地址: " + hostAddress);
    } catch (UnknownHostException e) {
        System.err.println("无法获取本机IP地址及主机名: " + e.getMessage());
        e.printStackTrace();
    }
}

}

4.Java 实例 – 获取远程文件大小
import java.net.URL;
import java.net.URLConnection;

public class Main {
public static void main(String[] args) throws Exception {

  int size;
  URL url = new URL("http://www.runoob.com/wp-content/themes/runoob/assets/img/newlogo.png");
  URLConnection conn = url.openConnection();
  size = conn.getContentLength();
  if (size < 0)
      System.out.println("无法获取文件大小。");
  else
    System.out.println("文件大小为：" + size + " bytes");
  conn.getInputStream().close();

}
}

5.Java 实例 – Socket 实现多线程服务器程序
import java.io.*;
import java.net.*;

public class MultiThreadedServer {

public static void main(String[] args) {
    int port = 12345; // 定义服务器端口
    try (ServerSocket serverSocket = new ServerSocket(port)) {
        System.out.println("服务器已启动，等待客户端连接...");

        while (true) {
            Socket clientSocket = serverSocket.accept(); // 接受客户端连接
            System.out.println("客户端已连接: " + clientSocket.getInetAddress().getHostAddress());

            // 为每个客户端连接启动一个新的线程
            ClientHandler clientHandler = new ClientHandler(clientSocket);
            new Thread(clientHandler).start();
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

}

class ClientHandler implements Runnable {

private Socket clientSocket;

public ClientHandler(Socket socket) {
    this.clientSocket = socket;
}

@Override
public void run() {
    try (
        InputStream input = clientSocket.getInputStream();
        OutputStream output = clientSocket.getOutputStream();
        BufferedReader reader = new BufferedReader(new InputStreamReader(input));
        PrintWriter writer = new PrintWriter(output, true)
    ) {
        String clientMessage;
        while ((clientMessage = reader.readLine()) != null) {
            System.out.println("收到客户端消息: " + clientMessage);
            writer.println("服务器回应: " + clientMessage); // 发送回应消息给客户端
        }
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        try {
            clientSocket.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

}

6.Java 实例 – 查看主机指定文件的最后修改时间
import java.net.URL;
import java.net.URLConnection;
import java.util.Date;
import java.text.SimpleDateFormat;

public class Main {

public static void main(String[] argv) throws Exception {
    URL u = new URL("http://127.0.0.1/test/test.html");
    URLConnection uc = u.openConnection();
    SimpleDateFormat ft = new SimpleDateFormat ("yyyy-MM-dd hh:mm:ss");
    uc.setUseCaches(false);
    long timestamp = uc.getLastModified();
    System.out.println("test.html 文件最后修改时间 :" + ft.format(new Date(timestamp)));
}

}

7.Java 实例 – 使用 Socket 连接到指定主机
import java.net.InetAddress;
import java.net.Socket;

public class WebPing {

public static void main(String[] args) {
    try {
        InetAddress addr;
        Socket sock = new Socket("www.runoob.com", 80);
        addr = sock.getInetAddress();
        System.out.println("连接到 " + addr);
        sock.close();
    } catch (java.io.IOException e) {
        System.out.println("无法连接 " + args[0]);
        System.out.println(e);
    }
}

}

8.Java 实例 – 网页抓取
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.InputStreamReader;
import java.net.URL;

public class Main {
public static void main(String[] args)
throws Exception {

  URL url = new URL("http://www.runoob.com");
  BufferedReader reader = new BufferedReader
  (new InputStreamReader(url.openStream()));
  BufferedWriter writer = new BufferedWriter
  (new FileWriter("data.html"));
  String line;
  while ((line = reader.readLine()) != null) {
     System.out.println(line);
     writer.write(line);
     writer.newLine();
  }
  reader.close();
  writer.close();

}
}

9.Java 实例 – 获取 URL响应头的日期信息
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.Date;

public class Main{
public static void main(String args[])
throws Exception {

  URL url = new URL("http://www.runoob.com");
  HttpURLConnection httpCon = 
  (HttpURLConnection) url.openConnection();
  long date = httpCon.getDate();
  if (date == 0)
  System.out.println("无法获取信息。");
  else
  System.out.println("Date: " + new Date(date));

}
}

10.Java 实例 – 获取 URL 响应头信息
import java.io.IOException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Map;
import java.util.Set;

public class Main {

public static void main(String[] args) throws IOException{
    URL url = new URL("http://www.runoob.com");
    URLConnection conn = url.openConnection();
    
    Map headers = conn.getHeaderFields();
    Set<String> keys = headers.keySet();
    for( String key : keys ){
        String val = conn.getHeaderField(key);
        System.out.println(key+"    "+val);
    }
    System.out.println( conn.getLastModified() );
}

}

11.Java 实例 – 解析 URL
import java.net.URL;

public class Main {
public static void main(String[] args)
throws Exception {

  URL url = new URL("http://www.runoob.com/html/html-tutorial.html");
  System.out.println("URL 是 " + url.toString());
  System.out.println("协议是 " + url.getProtocol());
  System.out.println("文件名是 " + url.getFile());
  System.out.println("主机是 " + url.getHost());
  System.out.println("路径是 " + url.getPath());
  System.out.println("端口号是 " + url.getPort());
  System.out.println("默认端口号是 " 
  + url.getDefaultPort());

}
}

12.Java 实例 – ServerSocket 和 Socket 通信实例
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
public static void main(String[] args) {

  try {
     ServerSocket ss = new ServerSocket(8888);
     System.out.println("启动服务器....");
     Socket s = ss.accept();
     System.out.println("客户端:"+s.getInetAddress().getLocalHost()+"已连接到服务器");
     
     BufferedReader br = new BufferedReader(new InputStreamReader(s.getInputStream()));
     //读取客户端发送来的消息
     String mess = br.readLine();
     System.out.println("客户端："+mess);
     BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(s.getOutputStream()));
     bw.write(mess+"\n");
     bw.flush();
  } catch (IOException e) {
     e.printStackTrace();
  }

}
}

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.Socket;
import java.net.UnknownHostException;

public class Client {
public static void main(String[] args) {

  try {
     Socket s = new Socket("127.0.0.1",8888);
     
     //构建IO
     InputStream is = s.getInputStream();
     OutputStream os = s.getOutputStream();
     
     BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(os));
     //向服务器端发送一条消息
     bw.write("测试客户端和服务器通信，服务器接收到消息返回到客户端\n");
     bw.flush();
     
     //读取服务器返回的消息
     BufferedReader br = new BufferedReader(new InputStreamReader(is));
     String mess = br.readLine();
     System.out.println("服务器："+mess);
  } catch (UnknownHostException e) {
     e.printStackTrace();
  } catch (IOException e) {
     e.printStackTrace();
  }

}
}

十二.Java 线程
1.Java 实例 – 查看线程是否存活
public class TwoThreadAlive extends Thread {
public void run() {

  for (int i = 0; i < 10; i++) {
     printMsg();
  }

}

public void printMsg() {

  Thread t = Thread.currentThread();
  String name = t.getName();
  System.out.println("name=" + name);

}

public static void main(String[] args) {

  TwoThreadAlive tt = new TwoThreadAlive();
  tt.setName("Thread");
  System.out.println("before start(), tt.isAlive()=" + tt.isAlive());
  tt.start();
  System.out.println("just after start(), tt.isAlive()=" + tt.isAlive());
  for (int i = 0; i < 10; i++) {
     tt.printMsg();
  }
  System.out.println("The end of main(), tt.isAlive()=" + tt.isAlive());

}
}

2.Java 实例 – 获取当前线程名称
public class TwoThreadGetName extends Thread {
public void run() {

  for (int i = 0; i < 10; i++) {
     printMsg();
  }

}
public void printMsg() {

  Thread t = Thread.currentThread();
  String name = t.getName();
  System.out.println("name=" + name);

}
public static void main(String[] args) {

  TwoThreadGetName tt = new TwoThreadGetName();
  tt.start();
  for (int i = 0; i < 10; i++) {
     tt.printMsg();
  }

}
}

3.Java 实例 – 状态监测
class MyThread extends Thread{
boolean waiting= true;
boolean ready= false;
MyThread() {
}
public void run() {

  String thrdName = Thread.currentThread().getName();
  System.out.println(thrdName + " starting.");
  while(waiting) 
  System.out.println("waiting:"+waiting); 
  System.out.println("waiting...");
  startWait(); 
  try {
     Thread.sleep(1000);
  }
  catch(Exception exc) {
     System.out.println(thrdName + " interrupted.");
  }
  System.out.println(thrdName + " terminating.");

}
synchronized void startWait() {

  try {
     while(!ready) wait();
  }
  catch(InterruptedException exc) {
     System.out.println("wait() interrupted");
  }

}
synchronized void notice() {

  ready = true;
  notify();

}
}
public class Main {
public static void main(String args[])
throws Exception{

  MyThread thrd = new MyThread();
  thrd.setName("MyThread #1");
  showThreadStatus(thrd);
  thrd.start();
  Thread.sleep(50);
  showThreadStatus(thrd);
  thrd.waiting = false;
  Thread.sleep(50); 
  showThreadStatus(thrd);
  thrd.notice();
  Thread.sleep(50);
  showThreadStatus(thrd);
  while(thrd.isAlive()) 
  System.out.println("alive");
  showThreadStatus(thrd);

}
static void showThreadStatus(Thread thrd) {

  System.out.println(thrd.getName() + "Alive:=" + thrd.isAlive() + " State:=" + thrd.getState());

}
}

4.Java 实例 – 线程优先级设置
public class SimplePriorities extends Thread {
private int countDown = 5;
private volatile double d = 0;
public SimplePriorities(int priority) {

  setPriority(priority);
  start();

}
public String toString() {

  return super.toString() + ": " + countDown;

}
public void run() {

  while(true) {
     for(int i = 1; i < 100000; i++)
     d = d + (Math.PI + Math.E) / (double)i;
     System.out.println(this);
     if(--countDown == 0) return;
  }

}
public static void main(String[] args) {

  new SimplePriorities(Thread.MAX_PRIORITY);
  for(int i = 0; i < 5; i++)
  new SimplePriorities(Thread.MIN_PRIORITY);

}
}

5.Java 实例 – 死锁及解决方法
import java.util.Date;

public class LockTest {
public static String obj1 = "obj1";
public static String obj2 = "obj2";
public static void main(String[] args) {

  LockA la = new LockA();
  new Thread(la).start();
  LockB lb = new LockB();
  new Thread(lb).start();

}
}
class LockA implements Runnable{
public void run() {

  try {
     System.out.println(new Date().toString() + " LockA 开始执行");
     while(true){
        synchronized (LockTest.obj1) {
           System.out.println(new Date().toString() + " LockA 锁住 obj1");
           Thread.sleep(3000); // 此处等待是给B能锁住机会
           synchronized (LockTest.obj2) {
              System.out.println(new Date().toString() + " LockA 锁住 obj2");
              Thread.sleep(60 * 1000); // 为测试，占用了就不放
           }
        }
     }
  } catch (Exception e) {
     e.printStackTrace();
  }

}
}
class LockB implements Runnable{
public void run() {

  try {
     System.out.println(new Date().toString() + " LockB 开始执行");
     while(true){
        synchronized (LockTest.obj2) {
           System.out.println(new Date().toString() + " LockB 锁住 obj2");
           Thread.sleep(3000); // 此处等待是给A能锁住机会
           synchronized (LockTest.obj1) {
              System.out.println(new Date().toString() + " LockB 锁住 obj1");
              Thread.sleep(60 * 1000); // 为测试，占用了就不放
           }
        }
     }
  } catch (Exception e) {
     e.printStackTrace();
  }

}
}

6.Java 实例 – 获取线程id
public class Main extends Object implements Runnable {
private ThreadID var;

public Main(ThreadID v) {

this.var = v;

}

public void run() {

try {
  print("var getThreadID =" + var.getThreadID());
  Thread.sleep(2000);
  print("var getThreadID =" + var.getThreadID());
} catch (InterruptedException x) {
}

}

private static void print(String msg) {

String name = Thread.currentThread().getName();
System.out.println(name + ": " + msg);

}

public static void main(String[] args) {

ThreadID tid = new ThreadID();
Main shared = new Main(tid);

try {
  Thread threadA = new Thread(shared, "threadA");
  threadA.start();

  Thread.sleep(500);

  Thread threadB = new Thread(shared, "threadB");
  threadB.start();

  Thread.sleep(500);

  Thread threadC = new Thread(shared, "threadC");
  threadC.start();
} catch (InterruptedException x) {
}

}
}

class ThreadID extends ThreadLocal {
private int nextID;

public ThreadID() {

nextID = 10001;

}

private synchronized Integer getNewID() {

Integer id = new Integer(nextID);
nextID++;
return id;

}

protected Object initialValue() {

print("in initialValue()");
return getNewID();

}

public int getThreadID() {

Integer id = (Integer) get();
return id.intValue();

}

private static void print(String msg) {

String name = Thread.currentThread().getName();
System.out.println(name + ": " + msg);

}
}

7.Java 实例 – 线程挂起
public class SleepingThread extends Thread {
private int countDown = 5;
private static int threadCount = 0;
public SleepingThread() {

  super("" + ++threadCount);
  start();

}
public String toString() {

  return "#" + getName() + ": " + countDown;

}
public void run() {

  while (true) {
     System.out.println(this);
     if (--countDown == 0)
        return;
     try {
        sleep(100);
     }
     catch (InterruptedException e) {
        throw new RuntimeException(e);
     }
  }

}
public static void main(String[] args)
throws InterruptedException {

  for (int i = 0; i < 5; i++)
  new SleepingThread().join();
  System.out.println("线程已被挂起");

}
}

8.Java 实例 – 终止线程
public class ThreadInterrupt extends Thread
{

public void run() 
{ 
    try 
    { 
        sleep(50000);  // 延迟50秒 
    } 
    catch (InterruptedException e) 
    { 
        System.out.println(e.getMessage()); 
    } 
} 
public static void main(String[] args) throws Exception 
{ 
    Thread thread = new ThreadInterrupt(); 
    thread.start(); 
    System.out.println("在50秒之内按任意键中断线程!"); 
    System.in.read(); 
    thread.interrupt(); 
    thread.join(); 
    System.out.println("线程已经退出!"); 
}

}

9.Java 实例 – 生产者/消费者问题
/*
author by runoob.com
ProducerConsumerTest.java
*/

public class ProducerConsumerTest {
public static void main(String[] args) {

  CubbyHole c = new CubbyHole();
  Producer p1 = new Producer(c, 1);
  Consumer c1 = new Consumer(c, 1);
  p1.start(); 
  c1.start();

}
}
class CubbyHole {
private int contents;
private boolean available = false;
public synchronized int get() {

  while (available == false) {
     try {
        wait();
     }
     catch (InterruptedException e) {
     }
  }
  available = false;
  notifyAll();
  return contents;

}
public synchronized void put(int value) {

  while (available == true) {
     try {
        wait();
     }
     catch (InterruptedException e) { 
     } 
  }
  contents = value;
  available = true;
  notifyAll();

}
}

class Consumer extends Thread {
private CubbyHole cubbyhole;
private int number;
public Consumer(CubbyHole c, int number) {

  cubbyhole = c;
  this.number = number;

}
public void run() {

  int value = 0;
     for (int i = 0; i < 10; i++) {
        value = cubbyhole.get();
        System.out.println("消费者 #" + this.number+ " got: " + value);
     }
}

}

class Producer extends Thread {
private CubbyHole cubbyhole;
private int number;

public Producer(CubbyHole c, int number) {

  cubbyhole = c;
  this.number = number;

}

public void run() {

  for (int i = 0; i < 10; i++) {
     cubbyhole.put(i);
     System.out.println("生产者 #" + this.number + " put: " + i);
     try {
        sleep((int)(Math.random() * 100));
     } catch (InterruptedException e) { }
  }

}
}

10.Java 实例 – 获取线程状态
// Java 程序 - 演示线程状态
class thread implements Runnable
{

public void run() 
{ 
    //  thread2  - 超时等待
    try
    { 
        Thread.sleep(1500); 
    }  
    catch (InterruptedException e)  
    { 
        e.printStackTrace(); 
    } 
      
    System.out.println("State of thread1 while it called join() method on thread2 -"+ 
        Test.thread1.getState()); 
    try
    { 
        Thread.sleep(200); 
    }  
    catch (InterruptedException e)  
    { 
        e.printStackTrace(); 
    }      
}

}

public class Test implements Runnable
{

public static Thread thread1; 
public static Test obj; 
  
public static void main(String[] args) 
{ 
    obj = new Test(); 
    thread1 = new Thread(obj); 
      
    // 创建 thread1，现在是初始状态
    System.out.println("State of thread1 after creating it - " + thread1.getState()); 
    thread1.start(); 
      
    // thread1 - 就绪状态
    System.out.println("State of thread1 after calling .start() method on it - " +  
        thread1.getState()); 
} 
  
public void run() 
{ 
    thread myThread = new thread(); 
    Thread thread2 = new Thread(myThread); 
      
    // 创建 thread1，现在是初始状态
    System.out.println("State of thread2 after creating it - "+ thread2.getState()); 
    thread2.start(); 
      
    // thread2 - 就绪状态
    System.out.println("State of thread2 after calling .start() method on it - " +  
        thread2.getState()); 
      
    // moving thread1 to timed waiting state 
    try
    { 
        //moving - 超时等待
        Thread.sleep(200); 
    }  
    catch (InterruptedException e)  
    { 
        e.printStackTrace(); 
    } 
    System.out.println("State of thread2 after calling .sleep() method on it - "+  
        thread2.getState() ); 
      
      
    try 
    { 
        // 等待 thread2 终止
        thread2.join(); 
    }  
    catch (InterruptedException e)  
    { 
        e.printStackTrace(); 
    } 
    System.out.println("State of thread2 when it has finished it's execution - " +  
        thread2.getState()); 
}

}

11.Java 实例 – 获取所有线程
public class Main extends Thread {
public static void main(String[] args) {

  Main t1 = new Main();
  t1.setName("thread1");
  t1.start();
  ThreadGroup currentGroup = 
  Thread.currentThread().getThreadGroup();
  int noThreads = currentGroup.activeCount();
  Thread[] lstThreads = new Thread[noThreads];
  currentGroup.enumerate(lstThreads);
  for (int i = 0; i < noThreads; i++)
  System.out.println("线程号：" + i + " = " + lstThreads[i].getName());

}
}

12.Java 实例 – 查看线程优先级
public class Main extends Object {
private static Runnable makeRunnable() {

  Runnable r = new Runnable() {
     public void run() {
        for (int i = 0; i < 5; i++) {
           Thread t = Thread.currentThread();
           System.out.println("in run() - priority="
           + t.getPriority()+ ", name=" + t.getName());
           try {
              Thread.sleep(2000);
           }
           catch (InterruptedException x) {
           }
        }
     }
  };
  return r;

}
public static void main(String[] args) {

  System.out.println("in main() - Thread.currentThread().getPriority()=" + Thread.currentThread().getPriority());
  System.out.println("in main() - Thread.currentThread().getName()="+ Thread.currentThread().getName());
  Thread threadA = new Thread(makeRunnable(), "threadA");
  threadA.start();
  try {
     Thread.sleep(3000);
  }
  catch (InterruptedException x) {
  }
  System.out.println("in main() - threadA.getPriority()="+ threadA.getPriority());

}
}

13.Java 实例 – 中断线程
public class Main extends Object
implements Runnable {
public void run() {

  try {
     System.out.println("in run() - 将运行 work2() 方法");
     work2();
     System.out.println("in run() - 从 work2() 方法回来");
  }
  catch (InterruptedException x) {
     System.out.println("in run() - 中断 work2() 方法");
     return;
  }
  System.out.println("in run() - 休眠后执行");
  System.out.println("in run() - 正常离开");

}
public void work2() throws InterruptedException {

  while (true) {
     if (Thread.currentThread().isInterrupted()) {
        System.out.println("C isInterrupted()=" + Thread.currentThread().isInterrupted());
        Thread.sleep(2000);
        System.out.println("D isInterrupted()=" + Thread.currentThread().isInterrupted());
     }
  }

}
public void work() throws InterruptedException {

  while (true) {
     for (int i = 0; i < 100000; i++) {
        int j = i * 2;
     }
     System.out.println("A isInterrupted()=" + Thread.currentThread().isInterrupted());
     if (Thread.interrupted()) {
        System.out.println("B isInterrupted()=" + Thread.currentThread().isInterrupted());
        throw new InterruptedException();
     }
  }

}
public static void main(String[] args) {

  Main si = new Main();
  Thread t = new Thread(si);
  t.start();
  try {
     Thread.sleep(2000);
  }
  catch (InterruptedException x) {
  }
  System.out.println("in main() - 中断其他线程");
  t.interrupt();
  System.out.println("in main() - 离开");

}
}

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java菜鸟教程学习（完整版）

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