深入解析FileInputStream和FileOutputStream

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FileInputStream和FileOutputStream类属于字节类，可以操作任意类型的文件。在数据流的处理过程中，有两种情况。
（1）以单个字节的形式读写文件
（2）以数据块的形式读写文件
从JDK的源码中，我们可以看出来：
FileInputStream的读：

 

1 2	public native int read() throws IOException; private native int readBytes(byte b[], int off, int len) throws IOException;

FileOutputStream的写：

 

1 2	public native void write(int b) throws IOException; private native void writeBytes(byte b[], int off, int len) throws IOException;

FileInputStream和FileOutputStream最常用的地方也就是文件的复制过程。下面通过两个例子来说明一下：
例子一：单个字节的读写

 

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public class Test {     public static void main(String[] args)     {         File src = new File("d:\\src.txt");         File dst = new File("d:\\dst.txt");         doSaveFile(src, dst);     }     public static void doSaveFile(File src, File dst)     {         InputStream in = null;         OutputStream out = null;         try         {             in = new FileInputStream(src);             out = new FileOutputStream(dst);             int len = 0;             while ((len = in.read()) > 0)             {//len表示读取的字节                 out.write(len);             }         }         catch (Exception e)         {         }         finally         {             if (null != in)             {                 try                 {                     in.close();                 }                 catch (IOException e)                 {                 }             }             if (null != out)             {                 try                 {                     out.close();                 }                 catch (IOException e)                 {                 }             }         }     } }

例子二：数据块的读写

 

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public class Test {     private final static int BUFFER_SIZE = 16 * 1024;     public static void main(String[] args)     {         File src = new File("d:\\src.txt");         File dst = new File("d:\\dst.txt");         doSaveFile(src, dst);     }     public static void doSaveFile(File src, File dst)     {         InputStream in = null;         OutputStream out = null;         try         {             in = new FileInputStream(src);             out = new FileOutputStream(dst);             byte[] buffer = new byte[BUFFER_SIZE];             int len = 0;             while ((len = in.read(buffer)) > 0)             {//len表示读取的字节数                 out.write(buffer, 0, len);             }         }         catch (Exception e)         {         }         finally         {             if (null != in)             {                 try                 {                     in.close();                 }                 catch (IOException e)                 {                 }             }             if (null != out)             {                 try                 {                     out.close();                 }                 catch (IOException e)                 {                 }             }         }     } }

疑问：
上面列出了两个例子，到底哪个例子的效率更高一些呢？
也许这个问题很难回答，因为效率的比对很难实现。而且数据流的底层实现，我们也很难搞清楚。其实，撇开这个问题，我们还有更高效的读取方式，那就是下一篇文章要讲的BufferedInputStream和BufferedOutputStream。
需要注意的是：
创建FileInputStream实例对象时，指定的文件应当是存在和可读的。创建FileOutputStream实例对象时，如果指定的文件已经存在，这个文件中的原来内容将被覆盖清除。

 

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