JAVA基础之java简单命令

java -cp命令
存在两个路径，其中psdir下com/test/training/路径下有Main.class和Student.class
另外路径，libdir下com/newtest/support/路径下有Other.class
在mydir下执行命令

//Windows
java -cp \psdir;\libdir com.test.training.Main
//Unix platforms
java -cp /psdir:/libdir com.test.training.Main

如果在psdir路径下，是training.jar包，包内com/test/training/路径下有Main.class和Student.class
另外路径，libdir下com/newtest/support/路径下有Other.class
在mydir下执行命令

//Windows
java -cp \psdir\training.jar;\libdir com.test.training.Main
//Unix platforms
java -cp /psdir/training.jar:/libdir com.test.training.Main

mydir路径下ourapp.jar，jar包内包含Manifest文件，以及com/test/training/路径下有Main.class和Student.class，com/newtest/support/路径下有Other.class

Manifest-Version: 1.0
Main-Class: com.test.training.Main

此时才可以执行

java -jar ourapp.jar

环境变量

//设置变量以及取出
Properties props = new Properties();
props.setProperty("displayName","Bu Xuesong");
String name = props.getProperty("displayName");
System.out.println("name:"+name);
String acctNum = props.getProperty("accountNumber");
System.out.println("acctNum:"+acctNum);
String nextPosition = props.getProperty("accountNumber","1");
System.out.println("nextPosition:"+nextPosition);

//获取系统变量
String username = System.getProperty("user.name");
System.out.println(username);
String userHome = System.getProperty("user.home");
System.out.println(userHome);
String osArchitecture = System.getProperty("os.arch");
System.out.println(osArchitecture);

String javaVendor = System.getProperty("java.vendor");
System.out.println(javaVendor);

Map<String,String> map = System.getenv();
for (String key:map.keySet()) {
    System.out.println("key:"+key+";value="+map.get(key));
}

String logName = System.getenv("LOGNAME");
System.out.println(logName);

将properties变量存入xml中

public static void XMLtest() {
    Properties prop = new Properties();
    prop.setProperty("displayName","Xuesong Bu");
    prop.setProperty("accountNumber","1-234-567");
    try(OutputStream out = Files.newOutputStream(Paths.get("/Users/buxuesong/Documents/svn_code/demo/prop.xml"))){
        prop.storeToXML(out,"My account");
    }catch (Exception e){
        System.out.println(e.getClass().getSimpleName()+" | "+e.getMessage());
    }

    Properties inProp = new Properties();
    try(InputStream in = Files.newInputStream(Paths.get("/Users/buxuesong/Documents/svn_code/demo/prop.xml"))){
        inProp.loadFromXML(in);
    }catch(Exception e){
        System.out.println(e.getClass().getSimpleName()+" | "+e.getMessage());
    }
    String displayName = inProp.getProperty("displayName");
    System.out.println("displayName:"+displayName);
    String accountNumber = inProp.getProperty("accountNumber");
    System.out.println("accountNumber:"+accountNumber);

}

生成的xml

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
<comment>My account</comment>
<entry key="displayName">Xuesong Bu</entry>
<entry key="accountNumber">1-234-567</entry>
</properties>
 输出的日志：
displayName:Xuesong Bu
accountNumber:1-234-567

默认Properties方式，当创建Properties的时候不必每次都去重新读区，可以通过之前的Properties构造方法来默认创建

public static void defaultProperties() {
    Properties defaults = new Properties();
    defaults.setProperty("position","1");
    Properties props = new Properties(defaults);

    String nextPos = props.getProperty("position");
    int pos = Integer.parseInt(nextPos);
    System.out.println("pos:"+pos);

    props.setProperty("position",Integer.toString(++pos));

    nextPos = props.getProperty("position");
    System.out.println("nextPos:"+nextPos);
}
输出：
pos:1
nextPos:2

通过读取默认的Properties以及将期存储为xml，后期可以再次取出。
以下程序在第一次执行时从默认MyDefaultValues.xml取出内容，放入userProps中，然后再将userProps存储到文件userValues.xml中，第二次执行就可以从userValues取出上一次存储的值

public class Main {

    public static void main(String[] args) {
        try{
            Properties defaultProps = new Properties();
            try(InputStream inputStream = Main.class.getClassLoader().getResourceAsStream("MyDefaultValues.xml")){
                defaultProps.loadFromXML(inputStream);
            }
            Properties userProps = new Properties(defaultProps);
            loadUserProps(userProps);
            String welcomeMessage = userProps.getProperty("welcomeMessage");
            String farewellMessage = userProps.getProperty("farewellMessage");
            System.out.println("welcomeMessage:"+welcomeMessage);
            System.out.println("farewellMessage:"+farewellMessage);

            if(userProps.getProperty("isFirstRun").equalsIgnoreCase("Y")){
                userProps.setProperty("welcomeMessage","Welcome back");
                userProps.setProperty("farewellMessage","Things will be familiar now");
                userProps.setProperty("isFirstRun","N");
                saveUserProps(userProps);
            }

        }catch (Exception e){
            System.out.println(e.getClass().getSimpleName()+" | "+e.getMessage());
        }
    }
    private static Properties loadUserProps(Properties userProps){
        Path userFile = Paths.get("/Users/buxuesong/Documents/svn_code/demo/userValues.xml");
        if(Files.exists(userFile)){
            try(InputStream inputStream = Files.newInputStream(userFile)){
                userProps.loadFromXML(inputStream);
            }catch (Exception e){
                System.out.println(e.getClass().getSimpleName()+" | "+e.getMessage());
            }
        }
        return userProps;
    }
    private static void saveUserProps(Properties userProps){
        try(OutputStream outputStream = Files.newOutputStream(Paths.get("/Users/buxuesong/Documents/svn_code/demo/userValues.xml"))){
            userProps.storeToXML(outputStream,null);
        }catch (Exception e){
            System.out.println(e.getClass().getSimpleName()+" | "+e.getMessage());
        }
    }
}

MyDefaultValues.xml内容为：

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
    <entry key="isFirstRun">Y</entry>
    <entry key="welcomeMessage">111Hello newcomer</entry>
    <entry key="farewellMessage">It'll all be different soon</entry>
</properties>

第一次运行输出：

welcomeMessage:111Hello newcomer
farewellMessage:It'll all be different soon

第二次运行输出：

welcomeMessage:Welcome back
farewellMessage:Things will be familiar now