几种基于javaI/O的文件拷贝操作比较

最近公司的项目用到文件拷贝，由于涉及到的大量大文件的拷贝工作，代码性能问题显得尤为重要，所以写了以下例子对几种文件拷贝操作做一比较：

0、文件拷贝测试方法

 1 public static void fileCopy(String source, String target,int type) {
 2         Date start = new Date();
 3         File in = null;
 4         File out = null;
 5         FileInputStream fis = null;
 6         FileOutputStream fos = null;
 7         try {
 8             in = new File(source);
 9             out = new File(target);
10             switch (type) {
11             case 1:
12                 copyer1(in, out, fis, fos);
13                 break;
14             case 2:
15                 copyer2(in, out, fis, fos);
16                 break;
17             case 3:
18                 copyer3(in, out, fis, fos);
19                 break;
20             case 4:
21                 copyer4(in, out, fis, fos);
22                 break;
23             default:
24                 break;
25             }
26         } catch (Exception e) {
27             e.printStackTrace();
28         } finally {
29             if (fis != null) {
30                 try {
31                     fis.close();
32                 } catch (IOException e) {
33                     e.printStackTrace();
34                 }
35             }
36             if (fos != null) {
37                 try {
38                     fos.close();
39                 } catch (IOException e) {
40                     e.printStackTrace();
41                 }
42             }
43             Date end = new Date();
44             System.out.println("方法"+type+"用时："+(end.getTime() - start.getTime())+" ms!");
45         }
46     }

方式一：一次读取全部数据

 1     /**
 2      * 一次全部读取文件内容
 3      */
 4     @SuppressWarnings("resource")
 5     public static void copyer1(File in,File out,FileInputStream fis,FileOutputStream fos) throws IOException{
 6         fis = new FileInputStream(in);
 7         int size = fis.available();
 8         byte[] buffer = new byte[size];
 9         fis.read(buffer);
10         fos = new FileOutputStream(out);
11         fos.write(buffer);
12         fos.flush();
13     }

方式二：每次读入固定字节的数据

 1     /**
 2      * 每次读取固定字节的数据
 3      */
 4     @SuppressWarnings("resource")
 5     public static void copyer2(File in,File out,FileInputStream fis,FileOutputStream fos) throws IOException{
 6
 7         fis = new FileInputStream(in);
 8         fos = new FileOutputStream(out);
 9         byte[] buffer = new byte[1024];
10         while (fis.read(buffer) != -1) {
11             fos.write(buffer);
12         }
13         fos.flush();
14     }

方式三：每次读取一行数据，适合按行解析数据的场景

 1     /**
 2      * 每次读取一行数据
 3      */
 4     @SuppressWarnings("resource")
 5     public static void copyer3(File in,File out,FileInputStream fis,FileOutputStream fos) throws IOException{
 6
 7         fis = new FileInputStream(in);
 8         fos = new FileOutputStream(out);
 9         BufferedReader br = new BufferedReader(new InputStreamReader(fis));
10         String line = null;
11         while ((line = br.readLine()) != null) {
12             fos.write(line.getBytes());
13         }
14         fos.flush();
15     }

方式四：每次读取一个字符，~_~，想想都累

 1     /**
 2      * 每次读取一个字节
 3      */
 4     @SuppressWarnings("resource")
 5     public static void copyer4(File in,File out,FileInputStream fis,FileOutputStream fos) throws IOException{
 6
 7         fis = new FileInputStream(in);
 8         fos = new FileOutputStream(out);
 9         int i = 0;
10         while ((i = fis.read()) != -1) {
11             fos.write(i);
12         }
13         fos.flush();
14     }
15 }

最后：测试用main函数

1     public static void main(String[] args) {
2         String source = "e:\\in.txt";
3         String target = "e:\\out.txt";
4         for (int i = 1; i < 5; i++) {
5             fileCopy(source, target, i);
6         }
7     }

测试文件：

运行结果：