//自己測試了一個3.8G的文件，有興趣的可以自己試試看，初學java寫的不對的地方希望大家能指出，有疑問可以留言一起探討，謝謝！

 1 package cn.String.Day.IO;
 2 
 3 import java.io.*;
 4 
 5 /**
 6  * Created by Void on 2017/6/20.
 7  */
 8         public class copyInputOutput {
 9             public static void main(String[] args) throws IOException {
10                 bufferTime();
 
11                 imbufferTime();
12 
13             }
14     private static void imbufferTime() throws IOException {
15         FileInputStream fileInputStream = new FileInputStream("D:\\360安全瀏覽器下載\\win7中文旗艦版64位系統.iso");
16         FileOutputStream fileOutputStream = new FileOutputStream("e:\\win7旗艦版64bit.iso");
 
17         long startTime = System.currentTimeMillis() ;
18         byte[] by = new byte[4096];
19         int len = 0;
20         while ((len = fileInputStream.read(by))!=-1){
21             fileOutputStream.write(by,0,len);
22 
23         }
24         fileOutputStream.close();
25         fileInputStream.close();
 
26         long endTime = System.currentTimeMillis();
27         System.out.println("自定義緩沖花費的時間是："+(endTime-startTime)/1000);
28     }
29 
30     private static void bufferTime() throws IOException {
31 
32         BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream("D:\\360安全瀏覽器下載\\win7中文旗艦版64位系統.iso"),4096);
33 
34         BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream("e:\\win7旗艦版64bit.iso"),4096);
35         long startTime = System.currentTimeMillis() ;
36         int len = 0;
37         while ((len = bufferedInputStream.read())!=-1){
38             bufferedOutputStream.write(len);
39 
40         }
41         bufferedOutputStream.close();
42         bufferedInputStream.close();
43         long endTime = System.currentTimeMillis();
44         System.out.println("原緩沖花費的時間是："+(endTime-startTime)/1000);
45     }
46 }

IO中關於自定義緩沖區和使用默認緩沖區哪個效率更高的對比