java nio

package com.nio;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.RandomAccessFile;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.channels.FileChannel.MapMode;

/**
 * 比较IO操作的性能比较：
 * 1、内存映射最快
 * 2、NIO读写文件
 * 3、使用了缓存的IO流
 * 4、无缓存的IO流
 * 
 * @author vince
 * @description
 */
public class CopyFileDemo {
    
    
    private static void randomAccessFileCopy() throws Exception{
        RandomAccessFile in = new RandomAccessFile("c:\\3D0.jpg","r");
        RandomAccessFile out = new RandomAccessFile("c:\\test\\3D0.jpg","rw");
        
        FileChannel fcIn = in.getChannel();
        FileChannel fcOut = out.getChannel();
        
        long size = fcIn.size();//输入流的字节大小
        //输入流的缓冲区
        MappedByteBuffer inBuf = fcIn.map(MapMode.READ_ONLY, 0, size);
        //输出流的缓冲区
        MappedByteBuffer outBuf = fcOut.map(MapMode.READ_WRITE, 0, size);
        
        for(int i=0;i<size;i++){
            outBuf.put(inBuf.get());
        }
        
        //关闭（关闭通道时会写入数据块）
        fcIn.close();
        fcOut.close();
        in.close();
        out.close();
        System.out.println("copy success");
    }
    
    /**
     * 通过文件通道实现文件的复制
     * @throws Exception
     */
    private static void copyFile() throws Exception{
        //创建一个输入文件的通道
        FileChannel fcIn = new FileInputStream("c:\\3D0.jpg").getChannel();
        //创建一个输出文件的通道
        FileChannel fcOut = new FileOutputStream("c:\\test\\3D0.jpg").getChannel();
        
        ByteBuffer buf = ByteBuffer.allocate(1024);
        while(fcIn.read(buf)!=-1){
            buf.flip();
            fcOut.write(buf);
            buf.clear();
        }
        fcIn.close();
        fcOut.close();
        System.out.println("copy success.");
    }

    public static void main(String[] args) {
        try {
//            copyFile();
            randomAccessFileCopy();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

}