java学习_小程序(四线程断点网络资源下载，即时进度反馈)

package com.netDemo;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;

public class MyThreadCopy extends Thread  {

/**
* 完成一个多线程断点下载工具
* 1.通过提供的网络文件地址，下载该文件
* 2.使用多个线程同时下载，并且实时更新下载进度(0%~100%)
* 3.能够实现断点功能
*/

private String sorce ;
private File target ;
privat
4000
e long start ;
private long end ;

public MyThreadCopy(String sorce,File target, long start, long end) {
this.sorce = sorce ;
this.target = target;
this.start = start;
this.end = end;
}

@Override
public void run() {
InputStream input = null ;
RandomAccessFile output = null;
long count = 0;
try {
URL url =  new URL(sorce);
HttpURLConnection conn =  (HttpURLConnection)url.openConnection();
conn.setRequestMethod("GET");
conn.setReadTimeout(100);
input =  conn.getInputStream();
output = new RandomAccessFile(target, "rw");

long total = conn.getContentLength();
File targetp = new File(target.getParent(),"copy");
ProgressReturn pr = new ProgressReturn (total,Long.valueOf(getName().substring(7)),targetp,target);
pr.start();
input.skip(start+pr.getCurrent());
output.seek(start+pr.getCurrent());
byte[] b = new byte[1024];
int len = 0;
while ((len = input.read(b)) != -1 && count <= (end - start)) {
sleep(1000);
output.write(b, 0, len);
count += len;
pr.setCurrent(count);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
try {
if (output != null)
output.close();
if (input != null)
input.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}

public static void main(String[] args) throws IOException {
String sorce = "http://img.taopic.com/uploads/allimg/131117/234805-13111FZ25393.jpg";
URL url =  new URL(sorce);
HttpURLConnection conn =  (HttpURLConnection)url.openConnection();
conn.setRequestMethod("GET");
conn.setReadTimeout(10000);
int code =	conn.getResponseCode();
if(code == HttpURLConnection.HTTP_OK){
long length = conn.getContentLength();
long needToCopy = length/4 ;
File target = new File ("C:\\Users\\ddf\\Desktop\\test",sorce.substring(sorce.lastIndexOf("/")));//新生成的目标文件 路径
for(int i = 0 ;i < 4 ;i++){
new MyThreadCopy(sorce,target,i*needToCopy,(i+1)*needToCopy).start();
}
}
}
}

package com.netDemo;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;

public class ProgressReturn extends Thread  {
private long total ;	//源文件要拷贝的总字节数目
private long current ;//记录当前所有线程共写了多少字节
private long index ;	//当前是哪个线程 由 thread.getId()传值;
private File targetP ;	//记录文件
private long ctotal ;	//当前四个进程一共写了多少
private File target ;   //要写入的目标文件

public ProgressReturn(long total, long index, File targetP,File target) {
super();
this.total = total;
this.index = index;
this.targetP = targetP;
this.target = target;
}

public  long getCurrent(){
return current; // 向外提供每个线程当前拷贝字节数 ，用于断点拷贝
}
public void setCurrent(long current){
this.current = current;
}

@Override
public void run() {
while(ctotal != total)
{
try {
RandomAccessFile raf = new RandomAccessFile(targetP,"rw");
raf.seek(index*8);
raf.writeLong(current);
ctotal = target.length();
System.out.println("当前总进程拷贝了:"+ctotal*1.0/total*100+"%");
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}

}
System.out.println("拷贝100%，完成");
if(	ctotal == total) {
if(targetP.exists())
{
targetP.delete();
}
System.out.println("已删除记录文件");
}

}
}