(转)四种复制文件的效率高低

四种复制文件的效率高低

package io2;

import java.io.*;

/**
 *
 * 测试复制的时间
 * Create by stefan
 * Date on 2018-05-28  10:28
 * Convertion over Configuration!
 */
public class copy2 {
    //一个字节一个字节的复制，耗时22697毫秒
    public static  void  fun() throws IOException {
        FileInputStream fis = new FileInputStream("F:\\汤包\\慕课大巴\\modern-java.pdf");
        FileOutputStream fos = new FileOutputStream("E:\\modern-java.pdf");
        int by = 0;
        while ((by=fis.read()) != -1) {
            fos.write(by);
            fos.flush();
        }
        fis.close();
        fos.close();
    }
    //1024字节数组复制 耗时63毫秒
    public  static void  fun1() throws IOException {
        FileInputStream fis = new FileInputStream("F:\\汤包\\慕课大巴\\modern-java.pdf");
        FileOutputStream fos = new FileOutputStream("E:\\modern-java.pdf");
        int len = 0;
        byte[] bytes =new byte[1024];
        while ((len=fis.read(bytes)) != -1) {
            fos.write(bytes,0,len);
            fos.flush();
        }
        fis.close();
        fos.close();
    }
    // 一个字节一个字节复制，但是用了缓冲流 耗时64毫秒
    public static   void  fun2() throws IOException {
        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("E:\\modern-java.pdf"));
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream("F:\\汤包\\慕课大巴\\modern-java.pdf"));
        int by = 0;
        while ((by=bis.read()) != -1) {
            bos.write(by);
            bos.flush();
        }
        bis.close();
        bos.close();
    }
    // 1024字节数组复制并用了缓冲流 耗时7毫秒
    public  static void  fun3() throws IOException {
        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream("E:\\modern-java.pdf"));
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream("F:\\汤包\\慕课大巴\\modern-java.pdf"));
        int len = 0;
        byte[] bytes =new byte[1024];
        while ((len=bis.read(bytes)) != -1) {
            bos.write(bytes,0,len);
            bos.flush();
        }
        bis.close();
        bos.close();
    }

    public static void main(String args[]) throws IOException {
        long t1 = System.currentTimeMillis();
        fun3();
        long t2 = System.currentTimeMillis();
        System.out.println(t2-t1);
    }

}

转自https://www.jianshu.com/p/63d1751d3eac