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

 public static void fileCopy(String source, String target,int type) {
         Date start = new Date();
         File in = null;
         File out = null;
         FileInputStream fis = null;
         FileOutputStream fos = null;
         try {
             in = new File(source);
             out = new File(target);
             switch (type) {
             case 1:
                 copyer1(in, out, fis, fos);
                 break;
             case 2:
                 copyer2(in, out, fis, fos);
                 break;
             case 3:
                 copyer3(in, out, fis, fos);
                 break;
             case 4:
                 copyer4(in, out, fis, fos);
                 break;
             default:
                 break;
             }
         } catch (Exception e) {
             e.printStackTrace();
         } finally {
             if (fis != null) {
                 try {
                     fis.close();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
             if (fos != null) {
                 try {
                     fos.close();
                 } catch (IOException e) {
                     e.printStackTrace();
                 }
             }
             Date end = new Date();
             System.out.println("方法"+type+"用时："+(end.getTime() - start.getTime())+" ms!");
         }
     }

方式一：一次读取全部数据

     /**
      * 一次全部读取文件内容
      */
     @SuppressWarnings("resource")
     public static void copyer1(File in,File out,FileInputStream fis,FileOutputStream fos) throws IOException{
         fis = new FileInputStream(in);
         int size = fis.available();
         byte[] buffer = new byte[size];
         fis.read(buffer);
         fos = new FileOutputStream(out);
         fos.write(buffer);
         fos.flush();
     }

方式二：每次读入固定字节的数据

     /**
      * 每次读取固定字节的数据
      */
     @SuppressWarnings("resource")
     public static void copyer2(File in,File out,FileInputStream fis,FileOutputStream fos) throws IOException{

         fis = new FileInputStream(in);
         fos = new FileOutputStream(out);
         byte[] buffer = new byte[1024];
         while (fis.read(buffer) != -1) {
             fos.write(buffer);
         }
         fos.flush();
     }

方式三：每次读取一行数据，适合按行解析数据的场景

     /**
      * 每次读取一行数据
      */
     @SuppressWarnings("resource")
     public static void copyer3(File in,File out,FileInputStream fis,FileOutputStream fos) throws IOException{

         fis = new FileInputStream(in);
         fos = new FileOutputStream(out);
         BufferedReader br = new BufferedReader(new InputStreamReader(fis));
         String line = null;
         while ((line = br.readLine()) != null) {
             fos.write(line.getBytes());
         }
         fos.flush();
     }

方式四：每次读取一个字符，~_~，想想都累

     /**
      * 每次读取一个字节
      */
     @SuppressWarnings("resource")
     public static void copyer4(File in,File out,FileInputStream fis,FileOutputStream fos) throws IOException{

         fis = new FileInputStream(in);
         fos = new FileOutputStream(out);
         int i = 0;
         while ((i = fis.read()) != -1) {
             fos.write(i);
         }
         fos.flush();
     }
 }

最后：测试用main函数

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

测试文件：

运行结果：