java Java 中的 ConcurrentLinkedQueue peek()方法

Java 中的 ConcurrentLinkedQueue peek()方法

原文:https://www . geeksforgeeks . org/concurrentlinkedqueue-peek-method-in-Java/

ConcurrentLinkedQueue 的 peek() 方法用于返回 ConcurrentLinkedQueue 的头。它检索但不移除这个 ConcurrentLinkedQueue 的头。如果 ConcurrentLinkedQueue 为空，则此方法返回 null。

语法:

public E peek()

返回:这个方法返回这个 ConcurrentLinkedQueue 的头而不删除它。

下面的程序说明了并发链接队列的 peek()方法:

例 1:

// Java Program Demonstrate peek()
// method of ConcurrentLinkedQueue

import java.util.concurrent.*;

public class GFG {
    public static void main(String[] args)
    {

        // create an ConcurrentLinkedQueue
        ConcurrentLinkedQueue<Integer>
            queue = new ConcurrentLinkedQueue<Integer>();

        // Add Numbers to queue
        queue.add(4353);
        queue.add(7824);
        queue.add(78249);
        queue.add(8724);

        // Displaying the existing ConcurrentLinkedQueue
        System.out.println("ConcurrentLinkedQueue: " + queue);

        // find peek
        int response1 = queue.peek();

        // print after applying peek method
        System.out.println("Head: " + response1);

        // Verifying that the head is not removed
        System.out.println("ConcurrentLinkedQueue after peek: " + queue);
    }
}

输出:

ConcurrentLinkedQueue: [4353, 7824, 78249, 8724]
Head: 4353
ConcurrentLinkedQueue after peek: [4353, 7824, 78249, 8724]

例 2:

// Java Program Demonstrate peek()
// method of ConcurrentLinkedQueue

import java.util.concurrent.*;

public class GFG {
    public static void main(String[] args)
    {

        // create an ConcurrentLinkedQueue
        ConcurrentLinkedQueue<String>
            queue = new ConcurrentLinkedQueue<String>();

        // Add String to queue
        queue.add("Aman");
        queue.add("Amar");
        queue.add("Sanjeet");
        queue.add("Rabi");

        // Displaying the existing ConcurrentLinkedQueue
        System.out.println("ConcurrentLinkedQueue: " + queue);

        // find peek of queue
        String response1 = queue.peek();

        // print after applying peek method
        System.out.println("Head: " + response1);

        // Verifying that the head is not removed
        System.out.println("ConcurrentLinkedQueue after peek: " + queue);

        // remove some elements
        queue.poll();
        queue.poll();

        // Displaying the existing ConcurrentLinkedQueue
        System.out.println("Updated ConcurrentLinkedQueue: " + queue);

        // find peek of queue
        String response2 = queue.peek();

        // print after applying peek method
        System.out.println("Head: " + response1);

        // Verifying that the head is not removed
        System.out.println("ConcurrentLinkedQueue after peek: " + queue);
    }
}

输出:

ConcurrentLinkedQueue: [Aman, Amar, Sanjeet, Rabi]

Head: Aman

ConcurrentLinkedQueue after peek: [Aman, Amar, Sanjeet, Rabi]

Updated ConcurrentLinkedQueue: [Sanjeet, Rabi]

Head: Aman

ConcurrentLinkedQueue after peek: [Sanjeet, Rabi]