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ArrayBlockingQueue peek() Method in Java
Last Updated : 11 Jul, 2025
ArrayBlockingQueue is bounded, blocking queue that stores the elements internally backed by an array.
ArrayBlockingQueue class is a member of the Java Collections Framework.
Bounded means it will have a fixed size, you can not store number the elements more than the capacity of the queue.
The queue also follows FIFO (first-in-first-out) rule for storing and removing elements from the queue.
If you try to put an element into a full queue or to take an element from an empty queue then the queue will block you.
The peek() method is used to return the head of the queue. It retrieves but does not remove, the head of this queue. If the queue is empty then this method returns null.
Syntax:
public E peek()
Parameters: The method does not take any parameters.
Return Value: The method returns the element present at the head of this queue.
Below programs illustrate peek() method of ArrayBlockingQueue.
Program 1:
Java
// Program to demonstrate peek() method of ArrayBlockingQueue
import java.util.concurrent.ArrayBlockingQueue;
public class GFG {
public static void main(String[] args) {
// Define capacity of ArrayBlockingQueue
int capacity = 5;
// Create object of ArrayBlockingQueue
ArrayBlockingQueue<Integer> queue =
new ArrayBlockingQueue<Integer>(capacity);
// Add element to ArrayBlockingQueue
queue.add(23);
queue.add(32);
queue.add(45);
queue.add(12);
// Print queue after adding numbers
System.out.println("After adding numbers queue is ");
System.out.println(queue);
// Print head of queue using peek() method
System.out.println("Head of queue "+queue.peek());
}
}
Output: After adding numbers queue is
[23, 32, 45, 12]
Head of queue 23
Program 2:
Java
// Program to demonstrate peek( ) method of ArrayBlockingQueue
import java.util.concurrent.ArrayBlockingQueue;
public class GFG {
// Create a User Object with name and age as the attribute
public class User{
public String name;
public String age;
User(String name,String age){
this.name=name;
this.age=age;
}
}
// Main Method
public static void main(String[] args) {
GFG gfg=new GFG();
gfg.offerExample();
}
// Method to give example of offer function
public void offerExample() {
// Define capacity of ArrayBlockingQueue
int capacity = 5;
// Create object of ArrayBlockingQueue
ArrayBlockingQueue<User> queue =
new ArrayBlockingQueue<User>(capacity);
// Create user objects
User user1=new User("Aman","24");
User user2=new User("Amar","23");
User user3=new User("Sanjeet","25");
User user4=new User("Suvo","26");
User user5=new User("Ravi","22");
// Add Objects to ArrayBlockingQueue
queue.offer(user1);
queue.offer(user2);
queue.offer(user3);
queue.offer(user4);
queue.offer(user5);
// Find peek of queue
User head=queue.peek();
// Print head
System.out.println("Details of First User Inserted");
System.out.println("User Name : "+head.name);
System.out.println("User Age : "+head.age);
}
}
