使用4个线程拷贝一个文件，实现断点下载。比如：这个文件500M，分四段下载。

package com.softeem.test8;import java.io.File;import java.io.FileNotFoundException;import java.io.IOException;import java.io.RandomAccessFile;public class ThreadFileCopy extends Thread {private File source;//源文件private File target;//目标文件private long start;//开始位置private long end;//结束位置public ThreadFileCopy(File source, File target, long start, long end) {super();this.source = source;this.target = target;this.start = start;this.end = end;}public void run() {System.out.println(this.getName()+"开始拷贝");int count = 0;RandomAccessFile rafread = null;RandomAccessFile rafwrite = null;try {rafread = new RandomAccessFile(source, "r");//只读rafwrite = new RandomAccessFile(target, "rw");//可读可写rafread.seek(start);rafwrite.seek(start);int len = 0;byte[] b = new byte[50];while ((len = rafread.read(b)) != -1 && count <= (end - start)) {//拷贝文件count += len;rafwrite.write(b, 0, len);}System.out.println(this.getName()+"完成");} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} finally {try {if (rafwrite != null)rafwrite.close();if (rafread != null)rafread.close();} catch (IOException e) {e.printStackTrace();}}}public static void main(String[] args) {File source = new File("d:\\larva搞笑虫子\\src.zip");//源文件File target = new File("d:\\目的\\src.zip");//目标文件long item = source.length() / 4;for (int i = 0; i < 4; i++) {new ThreadFileCopy(source, target, i * item, (i + 1) * item).start();//四个进程分段拷贝}}} 1_mr_tangshuaimr_tangshuai编辑预览