Java - Deque offer(E) Method

The Java Deque offer(E e) method inserts the specified element E at the end of this deque. It is similar to add() method.

Declaration

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

public boolean offer(E e)

Parameters

e − The element to be added at the end.

Return Value

This method returns true if the element was added to this deque, else false.

Exception

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

NullPointerException − if the specified element is null and this deque does not permit null elements.

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

Example 1

The following example shows the usage of Java Deque offer(E) method with Integers. We're adding few elements to list using add() method and then using offer() 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.offer(7);
      deque.offer(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 offer(E) method with Strings. We're adding few elements to list using add() method and then using offer() 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.offer("G");
      deque.offer("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 offer(E) method with Student objects. We're adding few elements to list using add() method and then using offer() 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 offer() method to add element at the end of the deque
      deque.offer(new Student(4, "Rohan"));
      deque.offer(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 ]]