Java ArrayDeque - peekFirst() Method

The java.util.ArrayDeque.peekFirst() method is used to retrieve the head (first element) of the deque. The method returns null, if the deque is empty. Unlike the ArrayDeque pollFirst method, it does not remove the retrieved element.

Syntax

public E peekFirst()

Here, E is the type of element maintained by the container.

Parameters

No parameter is required.

Return Value

Returns the head (first element) of the deque, or null if the deque is empty.

Exception

NA.

Example:

In the example below, the java.util.ArrayDeque.peekFirst() method is used to retrieve the head of the given deque.

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //creating a ArrayDeque
    ArrayDeque<Integer> MyDeque = new ArrayDeque<Integer>();

    //populating ArrayDeque 
    MyDeque.add(10);
    MyDeque.add(20);
    MyDeque.add(30);

    //printing ArrayDeque
    System.out.println("MyDeque contains: ");
    while(MyDeque.size() != 0) {
      System.out.println(MyDeque.peekFirst());
      MyDeque.removeFirst();
   }
  }
}

The output of the above code will be:

MyDeque contains: 
10
20
30