Java - Deque addLast() Method

The Java Deque addLast(E e) method inserts the specified element E at the end of the deque. It maintains the insertion order. When we calls this method multiple times, elements keeps appending to the list in the end of it.

Declaration

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

public void addLast(E e)

Parameters

e − The element to be added at the end.

Return Value

This method does not return any value.

Exception

IllegalStateException − if not all the elements can be added at this time due to insertion restrictions.

ClassCastException − if the class of an element of the specified collection prevents it from being added to this deque.

NullPointerException − if the specified collection contains a null element and this deque does not permit null elements, or if the specified collection is null.

IllegalArgumentException − if some property of an element of the specified collection prevents it from being added to this deque.

Example 1

The following example shows the usage of Java Deque addLast(E) method with Integers. We're adding few elements to list using add() method and then using addLast() method, we're adding two elements in the end. Lastly we're printing the Deque object to see the final result.

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(1);
      deque.add(2);
      deque.add(3);
      deque.add(4);        
      deque.add(5);
      deque.add(6);

      // the values will be printed in the same order
      deque.addLast(7);
      deque.addLast(8);

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

Output

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

Deque = [1, 2, 3, 4, 5, 6, 7, 8]

Example 2

The following example shows the usage of Java Deque addLast(E) method with Strings. We're adding few elements to list using add() method and then using addLast() method, we're adding two elements in the end. Lastly we're printing the Deque object to see the final result.

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");        
      deque.add("E");
      deque.add("F");

      // the values will be printed in the same order
      deque.addLast("G");
      deque.addLast("H");

      // let us print all the elements available in deque
      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, E, F, G, H]

Example 3

The following example shows the usage of Java Deque addLast(E) method with Student objects. We're adding few elements to list using add() method and then using addLast() method, we're adding two elements in the end. Lastly we're printing the Deque object to see the final result.

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<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"));

      // use addLast() method to add element at the end of the deque
      deque.addLast(new Student(4, "Rohan"));
      deque.addLast(new Student(5, "Sohan"));

      // let us print all the elements available in deque
      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 + " ]";
   }
}

Output

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

Deque = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ], [ 4, Rohan ], [ 5, Sohan ]]