Java ArrayDeque offerFirst(E) Method

Description

The Java ArrayDeque offerFirst(E e) method inserts the specified element E at the front of this deque. It is similar to addFirst() method.

Declaration

Following is the declaration for java.util.ArrayDeque.offerFirst() method

public boolean offerFirst(E e)

Parameters

e − The element to be added at the front.

Return Value

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

Exception

NullPointerException − if the specified element is null.

Example 1

The following example shows the usage of Java ArrayDeque offerFirst(E) method. In this example, we're using integers. As first, we'll add some items to the deque using add() method and then using offerFirst() method, we'll add elements to the front of the deque. Then we're adding more elements using add() method again and the print the array to check if insertions in the deque are in the order we desired.

package com.tutorialspoint;
import java.util.ArrayDeque;
import java.util.Deque;
public class ArrayDequeDemo {
   public static void main(String[] args) {
      
      // create an empty array deque
      Deque<Integer> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add(4);
      deque.add(5);
      deque.add(6);

      // use offerFirst() method to add element at the front of the deque
      deque.offerFirst(3);
      deque.offerFirst(2);
      deque.offerFirst(1);//now, element 1 will be at the front

      // these elements will be added in continuation with deque.add(6)
      deque.add(7);
      deque.add(8);

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

Output

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

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

Example 2

The following example shows the usage of Java ArrayDeque offerFirst(E) method. In this example, we're using strings. As first, we'll add some items to the deque using add() method and then using offerFirst() method, we'll add elements to the front of the deque. Then we're adding more elements using add() method again and the print the array to check if insertions in the deque are in the order we desired.

package com.tutorialspoint;
import java.util.ArrayDeque;
import java.util.Deque;
public class ArrayDequeDemo {
   public static void main(String[] args) {
      
      // create an empty array deque
      Deque<String> deque = new ArrayDeque<>();

      // use add() method to add elements in the deque
      deque.add("D");
      deque.add("E");
      deque.add("F");

      // use offerFirst() method to add element at the front of the deque
      deque.offerFirst("C");
      deque.offerFirst("B");
      deque.offerFirst("A");//now, element A will be at the front

      // these elements will be added in continuation with deque.add("F")
      deque.add("G");
      deque.add("H");

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

Output

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

ArrayDeque = [A, B, C, D, E, F, G, H]

Example 3

The following example shows the usage of Java ArrayDeque offerFirst(E) method. In this example, we're using Student objects. As first, we'll add some items to the deque using add() method and then using offerFirst() method, we'll add elements to the front of the deque. Then we're adding more elements using add() method again and the print the array to check if insertions in the deque are in the order we desired.

package com.tutorialspoint;
import java.util.ArrayDeque;
import java.util.Deque;
public class ArrayDequeDemo {
   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(4, "Julie"));
      deque.add(new Student(5, "Robert"));
      deque.add(new Student(6, "Adam"));

      // use offerFirst() method to add element at the front of the deque
      deque.offerFirst(new Student(3, "Rohan"));
      deque.offerFirst(new Student(2, "Sohan"));
      deque.offerFirst(new Student(1, "Mohan"));//now, Student 1 will be at the front

      // these elments will be added in continuation with deque.add(new Student(6, "Adam"))
      deque.add(new Student(7, "Ali"));
      deque.add(new Student(8, "Ahmad"));

      // let us print all the elements available in deque
      System.out.println("ArrayDeque = " + 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 −

ArrayDeque = [[ 1, Mohan ], [ 2, Sohan ], [ 3, Rohan ], [ 4, Julie ], [ 5, Robert ], [ 6, Adam ], [ 7, Ali ], [ 8, Ahmad ]]
java_util_arraydeque.htm
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