Java中的 ByteBuffer position() 方法及示例

Java.nio.ByteBuffer 类的position(int newPosition)方法用于设置这个缓冲区的位置。如果标记已定义且大于新位置，则将其丢弃。

句法：

public ByteBuffer position(int newPosition)

参数：该方法以newPosition为参数，即新的位置值。它必须是非负的并且不大于当前限制。

返回值：此方法返回此缓冲区。

以下是说明position()方法的示例：

示例 1：

// Java program to demonstrate
// position() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
        byte[] barr = { 10, 20, 30, 40 };
  
        // creating object of ByteBuffer
        // and allocating size capacity
        ByteBuffer bb = ByteBuffer.wrap(barr);
  
        // try to set the position at index 2
        // using position() method
        bb.position(2);
  
        // Set this buffer mark position
        bb.mark();
  
        // try to set the position at index 4
        // using position() method
        bb.position(4);
  
        // display position
        System.out.println("position before reset: "
                           + bb.position());
  
        // try to call reset() to restore
        // to the position we marked
        bb.reset();
  
        // display position
        System.out.println("position after reset: "
                           + bb.position());
    }
}

输出：

position before reset: 4
position after reset: 2

示例 2：

// Java program to demonstrate
// position() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
        // creating object of ByteBuffer
        // and allocating size capacity
        ByteBuffer bb = ByteBuffer.allocate(4);
  
        // try to set the position at index 1
        // using position() method
        bb.position(1);
  
        // putting the value of ByteBuffer
        // using put() method
        bb.put((byte)10);
  
        // try to set the position at index 3
        // using position() method
        bb.position(3);
  
        // putting the value of ByteBuffer
        // using put() method
        bb.put((byte)30);
  
        // display position
        System.out.println("ByteBuffer: "
                           + Arrays.toString(bb.array()));
    }
}

输出：

ByteBuffer: [0, 10, 0, 30]

参考： https://docs.oracle.com/javase/9/docs/api/ Java/nio/ByteBuffer.html#position-int-