javase多线程复制

package multiThread;

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

import org.junit.Test;

public class MultiThreadCopy {
    public void copy(String srcFile, String destFile) {
        File sf = new File(srcFile);
        // 源文件大小
        int length = (int) sf.length();
        // 线程数
        int count = 3;
        // 每个线程复制的大小
        int blockSize = length / count;
        for (int i = 0; i < count; i++) {
            int startPos = i * blockSize;
            int endPos = 0;
            if (i != (count - 1)) {
                endPos = (i + 1) * blockSize - 1;
            } else {
                endPos = length - 1;
            }
            // 开线程
            new ThreadCopy(srcFile, destFile, startPos, endPos).start();
        }
    }

    /**
     * 复制线程
     */
    class ThreadCopy extends Thread {
        private String srcFile;
        private String destFile;
        private int startPos;
        private int endPos;

        public ThreadCopy(String srcFile, String destFile, int startPos, int endPos) {
            super();
            this.srcFile = srcFile;
            this.destFile = destFile;
            this.startPos = startPos;
            this.endPos = endPos;
        }

        public void run() {
            try {
                // 源文件
                RandomAccessFile srcRaf = new RandomAccessFile(srcFile, "r");
                // 目标文件
                RandomAccessFile destRaf = new RandomAccessFile(destFile, "rw");
                // 定位读存位置
                srcRaf.seek(startPos);
                destRaf.seek(startPos);
                // 读取的字节数
                int bytes = endPos - startPos + 1;
                byte[] buf = new byte[1024];
                int len = 0;
                // 读取次数
                int count = bytes / buf.length;
                for (int i = 0; i < count; i++) {
                    // 最后一次读取
                    if (i == (count - 1)) {
                        if ((bytes % buf.length) != 0) {
                            buf = new byte[buf.length + (bytes % buf.length)];
                            srcRaf.read(buf);
                            destRaf.write(buf);
                        } else {
                            srcRaf.read(buf);
                            destRaf.write(buf);
                        }
                        srcRaf.close();
                        destRaf.close();

                    } else {
                        srcRaf.read(buf);
                        destRaf.write(buf);
                    }
                }

            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
    @Test
    public static void main(String[] args){
        MultiThreadCopy mt = new MultiThreadCopy();
        String src="E:\大数据资料\文件\java基础\视频\day09\day01_01集合的复习.avi";
        String des="E:\day01_01集合的复习.avi";
        mt.copy(src, des);
    }
}