Java ArrayBlockingQueue peek() Method

The peek() method of Java ArrayBlockingQueue class retrieves the head of this queue, but doesn't remove it. The method returns null if this queue is empty.

Syntax:

Parameters:

Specified By:

The peek() method of ArrayBlockingQueue class is specified by peek() method in interface Queue.

Return Value:

The peek() method returns this queue's head and if this queue is empty,it returns null.

Example 1

import java.util.concurrent.ArrayBlockingQueue;
public class ArrayBlockingQueuePeekExample1 {
    public static void main(String[] args) {
        int capacity =100;
        ArrayBlockingQueue<String> queue = new ArrayBlockingQueue<String>(capacity);
        queue.add("Reema");
        queue.add("Rahul");
        queue.add("Rita");
        queue.add("Ramesh");
        //peek() method will retrieve the head of the queue
        System.out.println("Head of queue : "+queue.peek());
        //peek() will not remove the head from the queue
        System.out.println("        Queue : "+queue);
    }
}

Output:

Head of queue : Reema
        Queue : [Reema, Rahul, Rita, Ramesh]

Example 2

import java.util.Queue;
import java.util.concurrent.ArrayBlockingQueue;
class Student {
    int marks;
    String name;
    public Student(int marks, String name) {
        this.marks = marks;
        this.name = name;
    }
   public String toString(){
        return this.name+" got "+ this.marks +" marks.";
   }
}
public class ArrayBlockingQueuePeekExample2 {
    public static void main(String[] args) {
        Student student1 = new Student(97,"Hinna");
        Student student2 = new Student(87,"Vinni");
        Student student3 = new Student(77,"Rima");
        int capacity =100;
        Queue<Student> queue = new ArrayBlockingQueue<Student>(capacity);
        queue.add(student1);
        queue.add(student2);
        queue.add(student3);
         for (Student xyz : queue){
             System.out.println(xyz);
         }
        System.out.println();
       System.out.println("Topper of the class is "+queue.peek().name);
    }
}

Output:

Hinna got 97 marks.
Vinni got 87 marks.
Rima got 77 marks.
Topper of the class is Hinna

Example 3

import java.util.concurrent.ArrayBlockingQueue;
public class ArrayBlockingQueuePeekExample3 {
    public static void main(String[] args) {
        int capacity =100;
        ArrayBlockingQueue<String> queue = new ArrayBlockingQueue<String>(capacity);
        queue.add("Reema");
        queue.add("Rahul");
        queue.add("Rita");
        queue.add("Ramesh");
        queue.clear();
        String val = queue.peek();
        System.out.println("Head of queue is : "+val);
    }
}

Output: