Java中的 FloatBuffer clear() 方法及示例

Java.nio.FloatBuffer类的clear()方法用于清除这个缓冲区。该方法将位置和限制分别设置为零和容量并丢弃标记。当有任何必要的通道读取或放置操作序列时，应调用此方法。这意味着如果需要读取缓冲区，则 clear() 方法使缓冲区准备好并将位置设置为零。例如：

buf.clear();     // Prepare buffer for reading
in.read(buf);    // Read data

该方法实际上并没有擦除缓冲区中的数据，但它被命名为好像它确实删除了一样，因为它最常用于可能出现删除的情况。

句法：

public final FloatBuffer clear()

参数：该方法不带任何参数。

返回值：此方法在清除其中的所有数据后返回此 FloatBuffer 实例。

以下是说明 clear() 方法的示例：

示例 1：

// Java program to demonstrate
// clear() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        try {
  
            float[] farr = { 2.5f, 3.5f, 4.5f, 6.7f };
  
            // 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 clear() to restore
            // to the position at index 0
            // by discarding the mark
            fb.clear();
  
            // display position
            System.out.println("position after reset: "
                               + fb.position());
        }
  
        catch (InvalidMarkException e) {
            System.out.println("new position is less than "
                               + "the position we "
                               + "marked before ");
            System.out.println("Exception throws: " + e);
        }
    }
}

输出：

position before reset: 4
position after reset: 0

示例 2：

// Java program to demonstrate
// clear() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        float[] farr = { 2.4f, 105.4f, 13.9f, 23.45f };
  
        // creating object of FloatBuffer
        // and allocating size capacity
        FloatBuffer fb = FloatBuffer.wrap(farr);
  
        // try to set the position at index 3
        fb.position(3);
  
        // display position
        System.out.println("position before clear: "
                           + fb.position());
  
        // try to call clear() to restore
        // to the position at index 0
        // by discarding the mark
        fb.clear();
  
        // display position
        System.out.println("position after clear: "
                           + fb.position());
    }
}

输出：

position before clear: 3
position after clear: 0

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