Java ConcurrentLinkedDeque peek()用法及代码示例

Java中的java.util.ConcurrentLinkedDeque.peek()方法用于检索或获取Deque头部的元素。检索到的元素不会从Deque中删除或删除，而是方法仅返回它。如果双端队列中没有元素，则返回Null。

用法:

Array_Deque.peek()

参数：该方法不带任何参数。

返回值：该方法返回双端队列顶部的元素。

以下程序说明了Java.util.ConcurrentLinkedDeque.peek()方法：

示例1:

// Java code to illustrate peek() 
  
import java.util.concurrent.*; 
  
public class ConcurrentLinkedDequeDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty ConcurrentLinkedDeque 
        ConcurrentLinkedDeque<String> de_que 
            = new ConcurrentLinkedDeque<String>(); 
  
        // Use add() method to add elements into the Deque 
        de_que.add("Welcome"); 
        de_que.add("To"); 
        de_que.add("Geeks"); 
        de_que.add("4"); 
        de_que.add("Geeks"); 
  
        // Displaying the ConcurrentLinkedDeque 
        System.out.println("Initial ConcurrentLinkedDeque: "
                           + de_que); 
  
        // Displaying the head 
        System.out.println("The element at head is: "
                           + de_que.peek()); 
  
        // Displaying the ConcurrentLinkedDeque after operation 
        System.out.println("Final ConcurrentLinkedDeque: "
                           + de_que); 
    } 
}

输出：

Initial ConcurrentLinkedDeque: [Welcome, To, Geeks, 4, Geeks]
The element at head is: Welcome
Final ConcurrentLinkedDeque: [Welcome, To, Geeks, 4, Geeks]

示例2:

// Java code to illustrate peek() 
import java.util.concurrent.*; 
  
public class ConcurrentLinkedDequeDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty ConcurrentLinkedDeque 
        ConcurrentLinkedDeque<Integer> de_que 
            = new ConcurrentLinkedDeque<Integer>(); 
  
        // Use add() method to add elements into the Deque 
        de_que.add(10); 
        de_que.add(15); 
        de_que.add(30); 
        de_que.add(20); 
        de_que.add(5); 
  
        // Displaying the ConcurrentLinkedDeque 
        System.out.println("Initial ConcurrentLinkedDeque: "
                           + de_que); 
  
        // Displaying the head 
        System.out.println("The element at head is: "
                           + de_que.peek()); 
  
        // Displaying the ConcurrentLinkedDeque after operation 
        System.out.println("Final ConcurrentLinkedDeque: "
                           + de_que); 
    } 
}

输出：

Initial ConcurrentLinkedDeque: [10, 15, 30, 20, 5]
The element at head is: 10
Final ConcurrentLinkedDeque: [10, 15, 30, 20, 5]

示例3:对于空的双端队列：

// Java code to illustrate peek() 
import java.util.concurrent.*; 
  
public class ConcurrentLinkedDequeDemo { 
    public static void main(String args[]) 
    { 
        // Creating an empty ConcurrentLinkedDeque 
        ConcurrentLinkedDeque<Integer> de_que 
            = new ConcurrentLinkedDeque<Integer>(); 
  
        // Displaying the ConcurrentLinkedDeque 
        System.out.println("ConcurrentLinkedDeque: "
                           + de_que); 
  
        // Displaying the head 
        System.out.println("The element at head is: "
                           + de_que.peek()); 
    } 
}

输出：

ConcurrentLinkedDeque: []
The element at head is: null

相关用法

注：本文由纯净天空筛选整理自MerlynShelley大神的英文原创作品 ConcurrentLinkedDeque peek() method in Java with Example。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。