Java ArrayDeque push() Method

Description

The Java ArrayDeque push(E e) method pushes an element E onto the stack represented by this deque. Essentially it add the element at the front of the ArrayDeque object.

Declaration

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

public void push(E e)

Parameters

e − The element to be pushed in the deque.

Return Value

This method does not return any value.

Exception

NullPointerException − if the specified element is null.

Pushing an Element to an ArrayDeque of Integers Example

The following example shows the usage of Java ArrayDeque push(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 push() method, we'll add elements to the stack. Then we're adding more elements using add() method again and the print the arraydeque 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 push() method to add element at the front of the deque
      deque.push(3);
      deque.push(2);
      deque.push(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]

Pushing an Element to an ArrayDeque of Strings Example

The following example shows the usage of Java ArrayDeque push(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 push() method, we'll add elements to the stack. Then we're adding more elements using add() method again and the print the arraydeque 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 push() method to add element to the stack
      deque.push("C");
      deque.push("B");
      deque.push("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]

Pushing an Element to an ArrayDeque of Objects Example

The following example shows the usage of Java ArrayDeque push(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 push() 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 arraydeque 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 push() method to add element to the stack
      deque.push(new Student(3, "Rohan"));
      deque.push(new Student(2, "Sohan"));
      deque.push(new Student(1, "Mohan"));//now, Student 1 will be at the front

      // these elements 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 ]]