NIO使用示例

/**  
* @Title: BuffTest.java   
* @Description: Buffer ByteBuffer LongBuffer IntegerBuffer FloatBuffer DoubleBuffer
* 缓存区分为两种，一种是直接缓冲区  另一种非缓冲区
* 非直接缓冲区主要存放在jvm缓存区中，来回拷贝
* 直接缓冲区--存放在物理内存中
* @author pcm  
* @date 2018年6月8日 下午5:22:27
* @version V1.0  
*/
public class BuffTest {

	/**
	 *Position 缓冲区正在操作的位置默认从0开始
	 *limit 写数据时，limit表示可对Buffer最多写入多少个数据。 读数据时，limit表示Buffer里有多少可读数据（not null的数据），
	 *capacity 缓冲区最大容量 一旦声明不能改变
	 *核心方法：
	 *put() 往buff存放数据
	 *get() 获取数据 
	 */
	@Test
	public void test001() {
		ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
		System.out.println(byteBuffer.position());
		System.out.println(byteBuffer.limit());
		System.out.println(byteBuffer.capacity());
		System.out.println("往bytebuffer里存放数据。。。");
		byteBuffer.put("123abc一二三".getBytes());
		System.out.println(byteBuffer.position());
		System.out.println(byteBuffer.limit());
		System.out.println(byteBuffer.capacity());

		System.out.println("往bytebuffer里读取数据。。。");
		byteBuffer.flip();// 开启读取模式
		System.out.println(byteBuffer.position());
		System.out.println(byteBuffer.limit());
		System.out.println(byteBuffer.capacity());
		byte[] bytes = new byte[byteBuffer.limit()];
		byteBuffer.get(bytes);
		System.out.println(new String(bytes, 0, bytes.length));

		System.out.println("往bytebuffer里重复读取数据。。。");
		byteBuffer.rewind();// 重复读取
		System.out.println(byteBuffer.position());
		System.out.println(byteBuffer.limit());
		System.out.println(byteBuffer.capacity());
		byte[] bytes2 = new byte[byteBuffer.limit()];
		byteBuffer.get(bytes2);
		System.out.println(new String(bytes2, 0, bytes.length));

		System.out.println("清空缓存区。。。");
		byteBuffer.clear(); 值不清空 下标清空
		System.out.println(byteBuffer.position());
		System.out.println(byteBuffer.limit());
		System.out.println(byteBuffer.capacity());
		System.out.println((char) byteBuffer.get());
	}

	/**
	* @Title: test002 
	* @Description: mark 和rest的用法   
	* @return void  
	* @throws
	 */
	@Test
	public void test002() {
		ByteBuffer byteBuffer = ByteBuffer.allocate(10);
		String str = "abcd";
		byteBuffer.put(str.getBytes());
		// 开启读的模式
		byteBuffer.flip();
		byte[] bytes = new byte[byteBuffer.limit()];
		byteBuffer.get(bytes, 0, 2);
		byteBuffer.mark(); // 打印标记
		System.out.println(new String(bytes, 0, 2));
		System.out.println(byteBuffer.position());
		System.out.println("=======================");
		byteBuffer.reset();// 还原到mark位置
		byteBuffer.get(bytes, 2, 2);
		System.out.println(new String(bytes, 0, 2));
		byteBuffer.reset();
		System.out.println("重置还原到mark标记");
		System.out.println(byteBuffer.position());
	}

	/**
	* @Title: test003 
	* @Description: 分散读取聚集写入
	* @throws IOException   
	* @return void  
	* @throws
	 */
	@Test
	public void test003() throws IOException {
		// 随机访问
		RandomAccessFile raf = new RandomAccessFile("test.txt", "rw");
		// 获取通信
		FileChannel channel = raf.getChannel();
		// 分配指定大小指定缓冲区
		ByteBuffer buf1 = ByteBuffer.allocate(100);
		ByteBuffer buf2 = ByteBuffer.allocate(1024);
		// 分散读取
		ByteBuffer[] bufs = { buf1, buf2 };
		channel.read(bufs);
		for (ByteBuffer buf : bufs) {
			// 切换成读模式
			buf.flip();
		}
		System.out.println(new String(bufs[0].array(), 0, bufs[0].limit()));
		System.out.println("-----------------------------");
		System.out.println(new String(bufs[1].array(), 1, bufs[1].limit()));
		System.out.println("-----------重复读取-------------");
		RandomAccessFile raf2 = new RandomAccessFile("test2.txt", "rw");
		// 获取通道
		FileChannel channel2 = raf2.getChannel();
		channel2.write(bufs);
		raf2.close();
		raf.close();
	}

	/**
	 * @throws CharacterCodingException 
	 * 
	* @Title: test004 
	* @Description: 编码格式   
	* @return void  
	* @throws
	 */

	@Test
	public void test004() throws CharacterCodingException {
		// 获取编码器
		Charset charset = Charset.forName("GBK");
		CharsetEncoder ce = charset.newEncoder();
		// 获取解码器
		CharsetDecoder cd = charset.newDecoder();
		CharBuffer charBuffer = CharBuffer.allocate(1024);
		charBuffer.put("解码器。。。");
		charBuffer.flip();
		// 编码
		ByteBuffer buffer = ce.encode(charBuffer);
		for (int i = 0; i < 6; i++) {
			System.out.println(buffer.get());
		}
		// 解码
		buffer.flip();
		// 编码解密
		CharBuffer decode = cd.decode(buffer);
		System.out.println(decode.toString());
		// Charset c2 = Charset.forName("utf-8");
		// CharBuffer decode2 = c2.newDecoder().decode(buffer);
		// System.out.println(decode2.toString());
	}