What is the ConcurrentLinkedDeque.peek() method in Java?

ConcurrentLinkedDeque is thread-safe, unbounded deque. The null value is not permitted as an element. We can use ConcurrentLinkedDeque when multiple threads share a single deque.

The peek method can be used to get the first element of the ConcurrentLinkedDeque object.

Syntax

public E peek()

Parameters

This method doesn’t take any parameters.

Return value

The peek method retrieves the first element of the deque object. If the deque is empty, then peek returns null

Code

The code below demonstrates how to use the peek method.

import java.util.concurrent.ConcurrentLinkedDeque;
class Peek {
    public static void main( String args[] ) {
      ConcurrentLinkedDeque<String> deque = new ConcurrentLinkedDeque<>();
      deque.add("1");
      deque.add("2");
      deque.add("3");
      System.out.println("The deque is " + deque);
      System.out.println("deque.peek() returns : " + deque.peek());
    }
}

Explanation

  • Line 1: We import the ConcurrentLinkedDeque class.

  • Line 4: We create a ConcurrentLinkedDeque object with the name deque.

  • Lines 5 to 7: We use the add() method of the deque object to add three elements ("1","2","3") to the deque.

  • Line 10: We use the peek() method of the deque object to get the first element of the deque. In our case, peek() returns 1.

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