Java中的 DoubleBuffer reset() 方法及示例

Java.nio.DoubleBuffer 类的reset()方法用于将此缓冲区的位置重置为先前标记的位置。在这种情况下，标记值既不会改变也不会被丢弃。它有助于恢复缓冲区中先前标记的值。

句法：

public final DoubleBuffer reset()

参数：该方法不带任何参数。

返回值：此方法返回此缓冲区。

以下是说明 reset() 方法的示例：

示例 1：

// Java program to demonstrate
// reset() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        try {
  
            double[] darr = { 10.5, 20.5, 30.5, 40.5 };
  
            // 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 reset() to restore
            // to the position we marked
            db.reset();
  
            // 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: 2

示例 2：

// Java program to demonstrate
// reset() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        try {
  
            double[] darr = { 10.5, 20.5, 30.5, 40.5 };
  
            // 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(1);
  
            // display position
            System.out.println("position before reset: "
                               + db.position());
  
            // try to call reset() to restore
            // to the position we marked
            db.reset();
  
            // display position
            System.out.println("position after reset: "
                               + db.position());
        }
  
        catch (InvalidMarkException e) {
            System.out.println("\nnew position is less than "
                               + "the position we"
                               + " marked before ");
            System.out.println("Exception throws: " + e);
        }
    }
}

输出：

position before reset: 1

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

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