[java][nio]三种流获得可写/可读可写/可读的通道

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

/**
 * 
 * 从流中获得通道
 * FileInputStream, FileOutputStream, RandomAccessFile
 *
 */
public class GetChannel {

	private static final int BSIZE = 1024;
	
	public static void main(String[] args) throws IOException {
		//写文件
		FileChannel fc = new FileOutputStream("d:\\a.txt").getChannel();
		fc.write(ByteBuffer.wrap("This is a test for nio.\n".getBytes()));
		fc.close();
		
		//向文件末尾添加数据
		fc = new RandomAccessFile("d:\\a.txt","rw").getChannel();
		//定位到文件末尾
		fc.position(fc.size());
		fc.write(ByteBuffer.wrap("This is the end of file.".getBytes()));
		fc.close();
		
		//读文件
		fc = new FileInputStream("D:\\a.txt").getChannel();
		ByteBuffer bb = ByteBuffer.allocate(BSIZE);
		fc.read(bb);
		//转换缓冲开关，由读转为写
		bb.flip();
		while(bb.hasRemaining()){
			System.out.print((char)bb.get());
		}
		fc.close();
	}

}