Java中的 FloatBuffer mark() 方法及示例

Java.nio.FloatBuffer 类的mark()方法用于将这个FloatBuffer 的当前位置标记为这个缓冲区的标记。

句法：

public final FloatBuffer mark()

参数：该方法不带任何参数。

返回值：该方法在将缓冲区的标记设置在当前位置后返回此 FloatBuffer。

下面的示例说明了 mark() 方法：

示例 1：

// Java program to demonstrate
// mark() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        try {
  
            float[] farr = { 10.5f, 20.5f, 30.5f, 40.5f };
  
            // creating object of FloatBuffer
            // and allocating size capacity
            FloatBuffer fb = FloatBuffer.wrap(farr);
  
            // try to set the position at index 2
            fb.position(2);
  
            // Set this buffer mark position
            // using mark() method
            fb.mark();
  
            // try to set the position at index 4
            fb.position(4);
  
            // display position
            System.out.println("position before reset: "
                               + fb.position());
  
            // try to call reset() to restore
            // to the position we marked
            fb.reset();
  
            // display position
            System.out.println("position after reset: "
                               + fb.position());
        }
  
        catch (InvalidMarkException e) {
            System.out.println("New position "
                               + "is less than "
                               + "the position "
                               + "marked before ");
            System.out.println("Exception throws: "
                               + e);
        }
    }
}

输出：

position before reset: 4
position after reset: 2

示例 2：演示 InvalidMarkException

// Java program to demonstrate
// mark() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        try {
  
            float[] farr = { 10.5f, 20.5f, 30.5f, 40.5f };
  
            // creating object of FloatBuffer
            // and allocating size capacity
            FloatBuffer fb = FloatBuffer.wrap(farr);
  
            // try to set the position at index 2
            fb.position(2);
  
            // Set this buffer mark position
            // using mark() method
            fb.mark();
  
            // try to set the position at index 1
            fb.position(1);
  
            // display position
            System.out.println("position before reset: "
                               + fb.position());
  
            // try to call reset() to restore
            // to the position we marked
            fb.reset();
  
            // display position
            System.out.println("position after reset: "
                               + fb.position());
        }
  
        catch (InvalidMarkException e) {
            System.out.println("\nNew position "
                               + "is less than "
                               + "the position "
                               + "marked before ");
            System.out.println("Exception throws: "
                               + e);
        }
    }
}

输出：

position before reset: 1

New position is less than the position marked before 
Exception throws: java.nio.InvalidMarkException

参考： https://docs.oracle.com/javase/9/docs/api/ Java/nio/FloatBuffer.html#mark–