Java代码 
- import java.io.*;
- class DownThread extends Thread {
- //定义字节数组（取水的竹筒）的长度
- private final int BUFF_LEN = 32;
- //定义读取的起始点
- private long start;
- //定义读取的结束点
- private long end;
- //读取文件对应的输入流
- private InputStream is;
- //将读取到的字节输出到raf中
- private RandomAccessFile raf;
- //构造器，传入输入流，输出流和读取起始点、结束点
- public DownThread(long start, long end, InputStream is, RandomAccessFile raf) {
- //输出该线程负责读取的字节位置
- System.out.println(start + "---->" + end);
- this.start = start;
- this.end = end;
- this.is = is;
- this.raf = raf;
- }
- public void run() {
- try {
- is.skip(start);
- raf.seek(start);
- //定义读取输入流内容的的缓存数组（竹筒）
- byte[] buff = new byte[BUFF_LEN];
- //本线程负责读取文件的大小
- long contentLen = end - start;
- //定义最多需要读取几次就可以完成本线程的读取
- long times = contentLen / BUFF_LEN + 4;
- //实际读取的字节数
- int hasRead = 0;
- for (int i = 0; i < times; i++) {
- hasRead = is.read(buff);
- //如果读取的字节数小于0，则退出循环！
- if (hasRead < 0) {
- break;
- }
- raf.write(buff, 0, hasRead);
- }
- } catch (Exception ex) {
- ex.printStackTrace();
- }
- //使用finally块来关闭当前线程的输入流、输出流
- finally {
- try {
- if (is != null) {
- is.close();
- }
- if (raf != null) {
- raf.close();
- }
- } catch (Exception ex) {
- ex.printStackTrace();
- }
- }
- }
- }
- public class MutilDown {
- public static void main(String[] args) {
- final int DOWN_THREAD_NUM = 4;
- final String OUT_FILE_NAME = "d:/copy勇敢的心.rmvb";
- InputStream[] isArr = new InputStream[DOWN_THREAD_NUM];
- RandomAccessFile[] outArr = new RandomAccessFile[DOWN_THREAD_NUM];
- try {
- isArr[0] = new FileInputStream("d:/勇敢的心.rmvb");
- long fileLen = getFileLength(new File("d:/勇敢的心.rmvb"));
- System.out.println("文件的大小" + fileLen);
- //以输出文件名创建第一个RandomAccessFile输出流
- outArr[0] = new RandomAccessFile(OUT_FILE_NAME, "rw");
- //创建一个与文件相同大小的空文件
- for (int i = 0; i < fileLen; i++) {
- outArr[0].write(0);
- }
- //每线程应该读取的字节数
- long numPerThred = fileLen / DOWN_THREAD_NUM;
- //整个文件整除后剩下的余数
- long left = fileLen % DOWN_THREAD_NUM;
- for (int i = 0; i < DOWN_THREAD_NUM; i++) {
- //为每个线程打开一个输入流、一个RandomAccessFile对象，
- //让每个线程分别负责读取文件的不同部分。
- if (i != 0) {
- isArr[i] = new FileInputStream("d:/勇敢的心.rmvb");
- //以指定输出文件创建多个RandomAccessFile对象
- outArr[i] = new RandomAccessFile(OUT_FILE_NAME, "rw");
- }
- if (i == DOWN_THREAD_NUM - 1) {
- //最后一个线程读取指定numPerThred+left个字节
- new DownThread(i * numPerThred, (i + 1) * numPerThred
- + left, isArr[i], outArr[i]).start();
- } else {
- //每个线程负责读取一定的numPerThred个字节
- new DownThread(i * numPerThred, (i + 1) * numPerThred,
- isArr[i], outArr[i]).start();
- }
- }
- } catch (Exception ex) {
- ex.printStackTrace();
- }
- }
- public static long getFileLength(File file) {
- long length = 0;
- //获取文件的长度
- long size = file.length();
- length = size;
- return length;
- }
- }
