Java中的 DoubleBuffer clear() 方法及示例

Java.nio.CharBuffer类的clear()方法用于清除这个缓冲区。在完成更改后清除此缓冲区时：

• 位置设置为零
• 限制设置为容量
• 标记被丢弃。

句法：

public final DoubleBuffer clear()

返回值：此方法在清除其中的所有数据后返回此 DoubleBuffer 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 {
  
            double[] darr = { 2.5, 3.5, 4.5, 6.7 };
  
            // creating object of DoubleBuffer
            // and allocating size capacity
            DoubleBuffer db
                = DoubleBuffer.wrap(darr);
  
            // try to set the position at index 2
            db.position(2);
  
            // Set this buffer mark position
            // using mark() method
            db.mark();
  
            // try to set the position at index 4
            db.position(4);
  
            // display position
            System.out.println("position before reset: "
                               + db.position());
  
            // try to call clear() to restore
            // to the position at index 0
            // by discarding the mark
            db.clear();
  
            // display position
            System.out.println("position after reset: "
                               + db.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)
    {
  
        double[] carr = { 2.4, 105.4, 13.9, 23.45d };
  
        // creating object of DoubleBuffer
        // and allocating size capacity
        DoubleBuffer db = DoubleBuffer.wrap(carr);
  
        // try to set the position at index 3
        db.position(3);
  
        // display position
        System.out.println("position before clear: "
                           + db.position());
  
        // try to call clear() to restore
        // to the position at index 0
        // by discarding the mark
        db.clear();
  
        // display position
        System.out.println("position after clear: "
                           + db.position());
    }
}

输出：

position before clear: 3
position after clear: 0

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