多线程切割文件Demo！！！

来源：互联网发布：远志多媒体教学软件编辑：程序博客网时间：2024/06/10 00:46
package mutithreaddown;import java.io.File;import java.io.FileInputStream;import java.io.RandomAccessFile;import java.util.concurrent.CountDownLatch;public class MutiThreadDownLoad2 {/**     * 同时下载的线程数     */    private int threadCount;    /**     * 服务器请求路径     */    private String sourcePath;    /**     * 本地路径     */    private String destinationPath;    /**     * 线程计数同步辅助     */    private CountDownLatch latch;        public MutiThreadDownLoad2(int threadCount, String sourcePath, String destinationPath, CountDownLatch latch) {        this.threadCount = threadCount;        this.sourcePath = sourcePath;        this.destinationPath = destinationPath;        this.latch = latch;    }    public void executeDownLoad() {        try {        File files = new File(sourcePath);                //服务器返回的数据的长度，实际上就是文件的长度,单位是字节                int length = (int) files.length();                System.out.println("文件总长度:" + length + "字节(B)");                RandomAccessFile raf = new RandomAccessFile(destinationPath, "rwd");                //指定创建的文件的长度                raf.setLength(length);                raf.close();                //分割文件                int blockSize = length / threadCount;                for (int threadId = 1; threadId <= threadCount; threadId++) {                    //第一个线程下载的开始位置                    int startIndex = (threadId - 1) * blockSize;                    int endIndex = startIndex + blockSize - 1;                    if (threadId == threadCount) {                        //最后一个线程下载的长度稍微长一点                        endIndex = length;                    }                    System.out.println("线程" + threadId + "下载:" + startIndex + "字节~" + endIndex + "字节");                    new DownLoadThread(threadId, startIndex, endIndex).start();                }        } catch (Exception e) {            e.printStackTrace();        }    }        /**     * 内部类用于实现下载     */    public class DownLoadThread extends Thread {        /**         * 线程ID         */        private int threadId;        /**         * 下载起始位置         */        private int startIndex;        /**         * 下载结束位置         */        private int endIndex;        public DownLoadThread(int threadId, int startIndex, int endIndex) {            this.threadId = threadId;            this.startIndex = startIndex;            this.endIndex = endIndex;        }        @Override        public void run() {            try {                System.out.println("线程" + threadId + "正在下载...");                File files = new File(sourcePath);                FileInputStream fis = new FileInputStream(files);                fis.skip(startIndex);                RandomAccessFile raf = new RandomAccessFile(destinationPath, "rwd");                //随机写文件的时候从哪个位置开始写                raf.seek(startIndex);//定位文件                int len = 0;                byte[] buffer = new byte[1024];                                //获取文件片段长度                int segLength = endIndex-startIndex+1;                                                while ((len = fis.read(buffer)) != -1) {                if(segLength>len){                segLength = segLength-len;                raf.write(buffer, 0, len);                }else{                raf.write(buffer,0,segLength);                break;                }                                   }                fis.close();                raf.close();                System.out.println("线程" + threadId + "下载完毕");                //计数值减一                latch.countDown();            } catch (Exception e) {                e.printStackTrace();            }        }    }            public static void main(String[] args) {int threadSize=4;String sourcePath = "D:\\新建文件夹\\小项目.rar";String destnationPath = "D:\\bbb.rar";CountDownLatch latch = new CountDownLatch(threadSize);MutiThreadDownLoad2 m = new MutiThreadDownLoad2(threadSize, sourcePath, destnationPath, latch);long startTime = System.currentTimeMillis();try {            m.executeDownLoad();            latch.await();        } catch (InterruptedException e) {            e.printStackTrace();        }        long endTime = System.currentTimeMillis();        System.out.println("全部下载结束,共耗时" + (endTime - startTime) / 1000 + "s");}    }控制台如下：文件总长度:120586816字节(B)线程1下载:0字节~30146703字节线程2下载:30146704字节~60293407字节线程1正在下载...线程3下载:60293408字节~90440111字节线程4下载:90440112字节~120586816字节线程2正在下载...线程4正在下载...线程3正在下载...线程1下载完毕线程3下载完毕线程2下载完毕线程4下载完毕全部下载结束,共耗时120s
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