Java - Deque peekLast() Method

The Java Deque peekLast() method retrieves the last element of the queue(but does not remove) represented by this deque.Returns null if this deque is empty.

Declaration

Following is the declaration for java.util.Deque.peekLast() method

public E peekLast()

Parameters

NA

Return Value

This method returns the last element of the queue represented by this deque, or null if this deque is empty.

Exception

NA

Example 1

The following example shows the usage of Java Deque peekLast() method with Integers. We're creating an Deque of Integers, adding some elements, print it and then use peekLast() method to get the last element. Deque remains untouched.

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;

public class DequeDemo {
   public static void main(String[] args) {
      
      // create an empty deque
      Deque<Integer> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add(25);
      deque.add(30);
      deque.add(20);
      deque.add(18);        

      // let us print all the elements available in deque
      System.out.println("Deque = " + deque);

      // it will retrieve last element
      System.out.println("Retrieved Element is = " + deque.peekLast());
	  
      // let us print all the elements available in deque again
      System.out.println("Deque = " + deque);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Deque = [25, 30, 20, 18]
Retrieved Element is = 18
Deque = [25, 30, 20, 18]

Example 2

The following example shows the usage of Java Deque peekLast() method with Strings. We're creating an Deque of Strings, adding some elements, print it and then use peekLast() method to get the last element. Deque remains untouched.

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;

public class DequeDemo {
   public static void main(String[] args) {
      
      // create an empty deque
      Deque<String> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add("A");
      deque.add("B");
      deque.add("C");
      deque.add("D");        

      // let us print all the elements available in deque
      System.out.println("Deque = " + deque);

      // it will retrieve last element
      System.out.println("Retrieved Element is = " + deque.peekLast());
	  
      // let us print all the elements available in deque again
      System.out.println("Deque = " + deque);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Deque = [A, B, C, D]
Retrieved Element is = D
Deque = [A, B, C, D]

Example 3

The following example shows the usage of Java Deque peekLast() method with Student objects. We're creating an Deque of Student objects, adding some students, print it and then use peekLast() method to get the last student. Deque remains untouched.

package com.tutorialspoint;

import java.util.ArrayDeque;
import java.util.Deque;

public class DequeDemo {
   public static void main(String[] args) {
      
      // create an empty array deque
      Deque<Student> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add(new Student(1, "Julie"));
      deque.add(new Student(2, "Robert"));
      deque.add(new Student(3, "Adam"));       

      // let us print all the elements available in deque
      System.out.println("Deque = " + deque);

      // it will retrieve last element
      System.out.println("Retrieved Element is = " + deque.peekLast());
	  
      // let us print all the elements available in deque again
      System.out.println("Deque = " + deque);
   }
}
class Student {
   int rollNo;
   String name;

   Student(int rollNo, String name){
      this.rollNo = rollNo;
      this.name = name;
   }

   @Override
   public String toString() {
      return "[ " + this.rollNo + ", " + this.name + " ]";
   }
   
   @Override
   public boolean equals(Object obj) {
      Student s = (Student)obj;
      return this.rollNo == s.rollNo && this.name.equalsIgnoreCase(s.name);
   }
}

Output

Let us compile and run the above program, this will produce the following result −

Deque = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]
Retrieved Element is = [ 3, Adam ]
Deque = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]