Java BlockingDeque peek()方法及示例

BlockingDeque 的 peek() 方法返回Deque容器中的前端元素。如果容器是空的，它将返回 null 。

语法

public E peek()

参数： 该方法不接受任何参数。

返回： 如果Deque容器不是空的，该方法返回该容器中的前端元素。如果容器是空的，它返回false。

注意 ： BlockingDeque 的peek()方法是继承自Java中的LinkedBlockingDeque类。

以下程序说明了BlockingDeque的peek()方法。

程序1 :

// Java Program Demonstrate peek()
// method of BlockingDeque
  
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
  
    {
  
        // create object of BlockingDeque
        BlockingDeque<Integer> BD
            = new LinkedBlockingDeque<Integer>();
  
        // Add numbers to end of BlockingDeque
        BD.add(7855642);
        BD.add(35658786);
        BD.add(5278367);
        BD.add(74381793);
  
        // Print the queue
        System.out.println("Linked Blocking Deque: " + BD);
  
        System.out.println("Front element in Deque: " + BD.peek());
    }
}

输出。

Linked Blocking Deque: [7855642, 35658786, 5278367, 74381793]
Front element in Deque: 7855642

程序2 :

// Java Program Demonstrate peek()
// method of BlockingDeque
// when Deque is empty
  
import java.util.concurrent.LinkedBlockingDeque;
import java.util.concurrent.BlockingDeque;
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
  
    {
  
        // create object of BlockingDeque
        BlockingDeque<Integer> BD
            = new LinkedBlockingDeque<Integer>();
  
        // Add numbers to end of BlockingDeque
        BD.add(7855642);
        BD.add(35658786);
        BD.add(5278367);
        BD.add(74381793);
  
        // Print the queue
        System.out.println("Blocking Deque: " + BD);
  
        // empty deque
        BD.clear();
  
        System.out.println("Front element in Deque: " + BD.peek());
    }
}

输出。

Blocking Deque: [7855642, 35658786, 5278367, 74381793]
Front element in Deque: null

**参考资料: **https: //docs.oracle.com/javase/7/docs/api/java/util/concurrent/BlockingDeque.html#peek()