Java NIO Buffer詳解

1、ByteBuffer類型化的put與get方法

/**
 * ByteBuffer類型化的put與get方法
 */
public class NioTest5 {

    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(64);

        buffer.putInt(5);
        buffer.putLong(500000000L);
        buffer.putDouble(13.456);
        buffer.putChar('你');
        buffer.putShort((short) 3);

        buffer.flip();

        System.out.println(buffer.getInt());
        System.out.println(buffer.getLong());
        System.out.println(buffer.getDouble());
        System.out.println(buffer.getChar());
        System.out.println(buffer.getShort());
    }
}

　　put和get的類型要一致。如第一個是putInt， 輸出的使用第一個要用getInt。

 

2、Slice Buffer

/**
 * Slice Buffer和原Buffer共享底層數組，任一一個改變，另一個也會改變
 */
public class NioTest6 {

    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(10);
        for(int i = 0; i < buffer.capacity(); ++i){
            buffer.put((byte)i);
        }

        buffer.position(2);
        buffer.limit(6);

        ByteBuffer sliceBuffer = buffer.slice();

        for(int i = 0; i < sliceBuffer.capacity(); ++i){
            byte b = sliceBuffer.get(i);
            b *= 2;
            sliceBuffer.put(i,  b);
        }

        buffer.position(0);
        buffer.limit(buffer.capacity());

       while (buffer.hasRemaining()){
           System.out.println(buffer.get());
       }
    }
}

　　

3、只讀Buffer

/**
 * 只讀buffer,咱們能夠隨時將一個普通Buffer調用asReadOnlyBuffer方法返回一個只讀Buffer
 * 但不能將一個只讀Buffer轉換爲讀寫Buffer
 */
public class NioTest7 {

    public static void main(String[] args) {
        ByteBuffer buffer = ByteBuffer.allocate(10);

        System.out.println(buffer.getClass());
        for(int i = 0; i < buffer.capacity(); ++i){
            buffer.put((byte)i);
        }

        ByteBuffer readonlyBuffer = buffer.asReadOnlyBuffer();
        System.out.println(readonlyBuffer.getClass());

        readonlyBuffer.position(0);
        readonlyBuffer.put((byte)2);


    }
}

　　對只讀Buffer進行修改，將拋出異常