【247天】我爱刷题系列（6）

叨叨两句

1. 越来越难啦！干死它们！

题15: 多线程下载

package com.test;

import java.io.File;
import java.io.FileFilter;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.URL;
import java.net.URLConnection;

public class DownloadThread extends Thread{
    
    //正在运行的线程个数
    public static int threadCount = 0;
    
    private int startIndex;
    private int endIndex;
    private String path;
    private int id;
    
    public DownloadThread() {
        
    }
    
    public DownloadThread(int startIndex, int endIndex, String path, int id) {
        this.startIndex = startIndex;
        this.endIndex = endIndex;
        this.path = path;
        this.id = id;
        threadCount++;
    }
    
    public void run() {
        try {
            //创建URL对象
            URL url = new URL(path);
            //建立连接
            URLConnection conn = url.openConnection();
            //配置连接
            conn.setRequestProperty("Range","bytes" + startIndex + "-" + endIndex);
            //通过连接获取流
            InputStream is = conn.getInputStream();
            
            FileOutputStream fos = new FileOutputStream(id + ".temp");
            
            byte[] arr = new byte[8 * 1024];
            int len;
            
            while((len = is.read(arr)) != -1) {
                fos.write(arr, 0, len);
            }
            
            is.close();
            fos.close();
            
            threadCount--;
            System.out.println(getName() + "下载完毕");
            
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

class FileUtil {
    public static void mergeFile(String srcPath,String destPath) throws Exception {
        File file = new File(srcPath);
        File[] subFiles = file.listFiles(new FileFilter() {
            public boolean accept(File pathname) {
                if(pathname.isFile() && pathname.getName().endsWith(".temp")) {
                    return true;
                }
                return false;
            }
        });
        
        FileOutputStream fos = new FileOutputStream(destPath);
        for (File subFile : subFiles) {
            FileInputStream fis = new FileInputStream(subFile);
            byte[] arr = new byte[8 * 1024];
            int len;
            while((len = fis.read(arr)) != -1) {
                fos.write(arr, 0, len);
            }
            fis.close();
        }
        fos.close();
        System.out.println("合并完毕");
    }
}

class ServerUtils {
    public static int getFileLength(String path) {
        try {
            URL url = new URL(path);
            URLConnection conn = url.openConnection();
            int fileLength = conn.getContentLength();
            return fileLength;
        } catch(Exception e) {
            return -1;
        }
    }
}

package com.test;

public class Test05 {

    public static void main(String[] args) throws Exception {
        String path = "http://ox4j4dsnp.bkt.clouddn.com/17-10-1/58878601.jpg";
        
        int length = ServerUtils.getFileLength(path);
        int count = 6;
        int perLength = length / count;
        for(int i = 0; i < count; i++) {
            int startIndex = perLength * i;
            int endIndex = perLength * (i + 1) - 1;
            if(i == count - 1) {
                endIndex = length - 1;
                System.out.println(endIndex);
            }
            new DownloadThread(startIndex, endIndex, path, i).start();
        }
        
        while(DownloadThread.threadCount > 0) {
            Thread.sleep(20);
        }
        
        FileUtil.mergeFile("D:\\workspace\\test","D:\\workspace\\test\\copy.jpg");
    }

}