AccessRandomFile multi-thread download file, accessrandomfile

AccessRandomFile multi-thread download file, accessrandomfile

 

Write a tool class

Package com. pb. thread. demo; import java. io. file; import java. io. fileNotFoundException; import java. io. IOException; import java. io. randomAccessFile;/*** multithread file copying tool class ** @ author denny **/public class MutiCopyFileUtil {private String src; // source file private String dst; // private int threadSize of the target file; // how many threads are enabled to copy the source file/*** constructor containing three parameters ** @ param src * Source File * @ param dst * target file * @ param threadSize * Enabled how many threads are used to copy source files? */Public MutiCopyFileUtil (String src, String dst, int threadSize) {super (); this. src = src; this. dst = dst; this. threadSize = threadSize;}/*** method of copying a File */public void copyFile () {file File = new File (src ); // File object of the source file // obtain the size of the source File in bytes long fsize = file. length (); // calculate the number of bytes downloaded by each thread. long block = fsize % threadSize = 0? Fsize/threadSize: fsize/threadSize + 1; // enable loop call for (int threadId = 0; threadId <threadSize; threadId ++) {// enable multiple threads to copy files, new DownloadThread (fsize, block, threadId ). start () ;}}/***** @ author denny **/private class DownloadThread extends Thread {private long fsize; // file size private long block; // The number of bytes downloaded by each thread private int threadId; // The thread ID, starting from 0 private int buffSize = 1024*1024; // the buffer size Public DownloadThread (long fsize, long block, int threadId) {super (); this. fsize = fsize; this. block = block; this. threadId = threadId;}/*** override the run Method */public void run () {try {// declare the IO class for randomly Accessing file objects, access the file RandomAccessFile reader = new RandomAccessFile (src, "r") in read-only mode; // randomly access the file object RandomAccessFile writer = new RandomAccessFile (dst, "rw "); // the start position of each thread to download long startPos = threadId * block; // determine the download position of each thread Long endPos = startPos + block> fsize? Fsize: startPos + block;/** determine whether the download end location is greater than the maximum position of the file. * If yes, it is the maximum position of the file, * No, it is the start position + the size of the byte to be downloaded * // you can specify the cursor position as reader. seek (startPos); // set the writer of the target file. seek (startPos); // set the buffer byte [] buf = new byte [buffSize]; while (startPos <endPos) {int len = 0; // determine whether it is to the end position if (startPos + buffSize <endPos) {// read the file to the buffer, read the file full len = reader. read (buf);} else {// write the remaining data that is not in the buffer zone to len = reader. read (buf, 0, (int) (endPos-startPos);} // change the starting position startPos + = len; /* write the target file * write the buffer file to the target file */writer. write (buf, 0, len); System. out. println ("Thread" + (threadId + 1) + "downloaded:" + len);} reader. close (); writer. close (); System. out. println ("Thread" + (threadId + 1) + "download completed");} catch (IOException e) {e. printStackTrace ();}}}}

Test class

package com.pb.thread.demo;import java.io.File;/** *  * @author denny * */public class MutiCopyFileDemo {    public static void main(String[] args) {        /*         * /home/denny/Downloads         * android-studio-ide-141.2135290-linux.zip         */        String src="/home/denny/Downloads/android-studio-ide-141.2135290-linux.zip";        String dst="/home/denny/Downloads/a.zip";        MutiCopyFileUtil mcf=new MutiCopyFileUtil(src,dst,10);        mcf.copyFile();    }}

 

Result:

Thread 9 download: 1048576 thread 6 download: 1048576 thread 4 download: 1048576 thread 3 download: 1048576 thread 1 download: 1048576 thread 8 download: 1048576 thread 2 download: 1048576 thread 5 download: 1048576 thread 7 download: 1048576 thread 10 download: 1048576 thread 9 download: 1048576 thread 1 download: 1048576 thread 7 download: 1048576 thread 3 download: 1048576 thread 6 download: 1048576 thread 4 download: 1048576 thread 2 download: 1048576 thread 10 download: 1048576 thread 3 download: 1048576 thread 8 download: 1048576 thread 6 download: 1048576 thread 5 download: 1048576 thread 1 download: 1048576 thread 4 download: 1048576 thread 7 download: 1048576 thread 9 download: 1048576 thread 2 download: 1048576 thread 4 download: 1048576 thread 6 download: 1048576 thread 8 download: 1048576 thread 7 download: 1048576 thread 9 download: 1048576 thread 1 download: 1048576 thread 2 download: 1048576 thread 5 download: 1048576 thread 3 download: 1048576 thread 7 download: 1048576 thread 10 download: 1048576 thread 2 download: 1048576 thread 5 download: 1048576 thread 2 download: 1048576 thread 9 download: 1048576 thread 4 download: 1048576 thread 10 download: 1048576 thread 5 download: 1048576 thread 10 download: 1048576 thread 9 download: 1048576 thread 4 download: 1048576 thread 2 download: 1048576 thread 5 download: 1048576 thread 3 download: 1048576 thread 8 download: 1048576 thread 10 download: 1048576 thread 9 download: 1048576 thread 1 downloaded: 1048576 thread 7 downloaded: 1048576 thread 6 downloaded: 1048576 thread 10 downloaded: 1048576 thread 4 downloaded: 1048576 thread 3 downloaded: 1048576 thread 9 download: 1048576 thread 1 download: 1048576 thread 8 download: 1048576 thread 6 download: 1048576 thread 4 download: 1048576 thread 10 download: 1048576 thread 5 download: 1048576 thread 7 download: 1048576 thread 3 download: 1048576 thread 1 download: 1048576 thread 9 download: 1048576 thread 2 download: 1048576 thread 5 download: 1048576 thread 4 download: 1048576 thread 10 download: 1048576 thread 1 download: 1048576 thread 2 download: 1048576 thread 1 download: thread 1 download: 1048576 thread 7 download: 1048576 thread 8 download: 1048576 thread 6 download: 1048576 thread 9 download: 1048576 thread 3 download: 1048576 thread 1 download: 1048576 thread 2 download: 1048576 thread 5 download: 1048576 thread 10 download: 1048576 thread 4 download: 1048576 thread 7 download: 1048576 thread 10 download: 1048576 thread 3 download: 1048576 thread 7 download: 1048576 thread 6 download: 1048576 thread 8 download: 1048576 thread 9 download: 1048576 thread 10 download: 1048576 thread 6 download: 1048576 thread 1 download: 1048576 thread 5 download: 1048576 thread 4 download: 1048576 thread 2 download: 1048576 thread 9 download: 1048576 thread 7 download: 1048576 thread 6 download: 1048576 thread 8 download: 1048576 thread 2 download: 1048576 thread 7 download: 1048576 thread 3 download: 1048576 thread 9 download: 1048576 thread 6 download: 1048576 thread 10 download: 1048576 thread 5 download: 1048576 thread 4 download: 1048576 thread 1 download: 1048576 thread 8 download: 1048576 thread 3 download: 1048576 thread 6 download: 1048576 thread 9 download: 1048576 thread 4 download: 1048576 thread 7 download: 1048576 thread 2 download: 1048576 thread 5 download: 1048576 thread 1 download: 1048576 thread 10 download: 1048576 thread 6 download: 1048576 thread 10 download: thread 10 download: 1048576 thread 9 download: 1048576 thread 1 download: 1048576 thread 8 download: 1048576 thread 5 download: 1048576 thread 3 download: 1048576 thread 4 download: 1048576 thread 7 download: 1048576 thread 2 download: 1048576 thread 10 download: 1048576 thread 6 download: 1048576 thread 9 download: 1048576 thread 5 download: 1048576 thread 10 download: 1048576 thread 8 download: 1048576 thread 7 download: 1048576 thread 1 download: 1048576 thread 2 download: 1048576 thread 4 download: 1048576 thread 6 download: 1048576 thread 10 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thread 6 download: 1048576 thread 1 download: 1048576 thread 6 download: 1048576 thread 5 download: thread 5 download: 1048576 thread 9 download: 1048576 thread 7 download: 1048576 thread 6 download: 1048576 thread 3 download: 1048576 thread 7 download: 1048576 thread 10 download: 1048576 thread 8 download: 1048576 thread 5 download: 1048576 thread 7 download: 1048576 thread 1 download: 1048576 thread 2 download: 1048576 thread 6 download: 1048576 thread 9 download: 1048576 thread 5 download: 1048576 thread 4 download: 1048576 thread 8 download: 1048576 thread 3 download: 1048576 thread 8 download: thread 8 download: 1048576 thread 7 download: 1048576 thread 7 download: 1048576 thread 7 download: 1048576 thread 7 download: 1048576 thread 6 download: 1048576 thread 3 download: 1048576 thread 8 download: 1048576 thread 5 download: 1048576 thread 9 download: 1048576 thread 10 download: 1048576 thread 2 download: 1048576 thread 4 download: 1048576 thread 2 download: 1048576 thread 1 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1048576 thread 6 download: 1048576 thread 6 download: 596259 thread 5 download: 1048576 thread 10 download: 1048576 thread 9 download: 1048576 thread 10 download: 1048576 thread 1 download: 1048576 thread 3 download: 1048576 thread 2 download: 1048576 thread 7 download: 1048576 thread 6 download completed thread 9 download: 1048576 thread 2 download: 1048576 thread 7 download: 1048576 thread 10 download: 1048576 thread 4 download: 1048576 thread 5 download: 1048576 thread 2 download: 1048576 thread 8 download: 1048576 thread 9 download: 1048576 thread 5 download: 1048576 thread 7 download: 1048576 thread 1 download: 1048576 thread 2 download: 1048576 thread 3 download: 1048576 thread 2 download: 1048576 thread 3 download: 1048576 thread 1 download: 1048576 thread 10 download: 1048576 thread 7 download: 1048576 thread 5 download: 1048576 thread 8 download: 1048576 thread 2 download: 1048576 thread 7 download: 596259 thread 7 download completed thread 10 download: 1048576 thread 4 download: 1048576 thread 9 download: 1048576 thread 3 download: 1048576 thread 1 download: 1048576 thread 10 download: 596259 thread 10 download completed thread 2 download: 1048576 thread 4 download: 1048576 thread 9 download: 1048576 thread 8 download: 1048576 thread 5 download: 1048576 thread 2 download: 596259 thread 2 download completed thread 3 download: 1048576 thread 1 download: 1048576 thread 3 download: 1048576 thread 4 download: 1048576 thread 1 download: 1048576 thread 9 download: 1048576 thread 8 download: 1048576 thread 3 download: 1048576 thread 4 download: 1048576 thread 5 download: 1048576 thread 8 download: 1048576 thread 9 download: 1048576 thread 3 download: 1048576 thread 5 download: 596259 thread 9 download: 1048576 thread 1 download: 1048576 thread 5 download completed thread 4 download: 1048576 thread 8 download: 1048576 thread 3 download: 1048576 thread 9 download: 1048576 thread 3 download: 1048576 thread 8 download: 1048576 thread 4 download: 1048576 thread 9 download: 596259 thread 9 download completed thread 1 download: 1048576 thread 4 download: 1048576 thread 3 download: 1048576 thread 8 download: 1048576 thread 1 download: 1048576 thread 4 download: 1048576 thread 8 download: 1048576 thread 3 download: 1048576 thread 1 download: 1048576 thread 4 download: 1048576 thread 3 download: 596259 thread 3 download completed thread 4 download: 596259 thread 1 download: 1 048576 thread 4 download completed thread 8 download: 1048576 thread 8 download: 596259 thread 8 download completed thread 1 download: 1048576 thread 1 download: 1048576 thread 1 download: thread 1 download: 596259 thread 1 download complete