NIO

 http://tutorials.jenkov.com/java-nio/socketchannel.html

 

package com.gc;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;

import junit.framework.TestCase;

public class Test extends TestCase{
	/**
	 * 通道
	 * 缓冲区
	 * 异步IO
	 * 直接缓冲区
	 */
	Charset utf8 = Charset.forName("UTF-8");
	
	CharsetEncoder encoder = utf8.newEncoder();
	CharsetDecoder decoder = utf8.newDecoder();
	
	
	//clear() 方法重设缓冲区，使它可以接受读入的数据。
	//Clears this buffer. The position is set to zero, the limit is set to the capacity, and the mark is discarded.
	public  void testReadWithCharset() throws Exception {
		String fileName = "test.txt";
		FileInputStream fin = new FileInputStream(fileName);
		FileChannel fc = fin.getChannel();
		
		ByteBuffer buffer = ByteBuffer.allocate(100);
		fc.read(buffer);
		
		//从缓冲区读之前必须调用flip()-->设置limit与position的位置
		buffer.flip();
		
		//使用Charset进行解码，正确显示中文
		CharBuffer charBuf = decoder.decode(buffer);
		
		while(charBuf.remaining()>0) {
			System.out.print(charBuf.get());
		}
		
		
		fin.close();
		
	}
	
	//flip() 方法重新调整position和limit在缓冲区数组中的位置，以便将读入的数据完整写入通道。
	//The limit is set to the current position and then the position is set to zero
	public void testWriteWithCharset()throws Exception {
		FileOutputStream fout = new FileOutputStream("write.txt");
		FileChannel fc = fout.getChannel();
		
		CharBuffer buffer = CharBuffer.allocate(1024);
		
		char[] message = {'该','睡','觉','了'};
		
		
		for(int i=0;i<message.length;i++) {
			buffer.put(message[i]);
		}
		
		buffer.flip();//编码之前先调用flip()

		//写数据，必须使用 CharsetEncoder将它转换回字节
		ByteBuffer byteBuf = encoder.encode(buffer);
		
		fc.write(byteBuf);
		
		fout.close();
		
	}
	
	
	//clear() 和 flip() 方法用于让缓冲区在读和写之间切换。 
	public void testCopy()throws Exception {
		
		FileInputStream fin = new FileInputStream("cp-source.txt");
		FileChannel fic = fin.getChannel();
		
		FileOutputStream fout = new FileOutputStream("cp-result.txt");
		FileChannel foc = fout.getChannel();
		
		ByteBuffer buffer = ByteBuffer.allocate(1024);
		
		while(true) {
			//read
			buffer.clear();
			int r = fic.read(buffer);
			
			if(r==-1)
				break;
			
			//write
			buffer.flip();
			foc.write(buffer);
		}
		
		fin.close();
		fout.close();
	}
	
}