Java ArrayDeque size() Method

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Description

The Java ArrayDeque size() method returns the number of elements in this deque. It is updated everytime a change is made to the ArrayDeque.

Declaration

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

public int size()

Parameters

NA

Return Value

This method returns the number of elements in this deque.

Exception

NA

Getting Size of an ArrayDeque of Integers Example

The following example shows the usage of Java ArrayDeque size() method with Integers. We're creating an ArrayDeque of Integers, adding some elements, print the size and then use remove() method to remove the first element. As ArrayDeque is modified its size is printed again.

package com.tutorialspoint;

import java.util.ArrayDeque;

public class ArrayDequeDemo {
   public static void main(String[] args) {
      
      // create an empty array deque
      ArrayDeque<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 the size of deque
      System.out.println("Size of ArrayDeque = " + deque.size());

      // it will retrieve first element after removing from deque
      deque.remove();
	  
      // let us print the size of deque again
      System.out.println("Size of ArrayDeque = " + deque.size());
   }
}

Output

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

Size of ArrayDeque = 4
Size of ArrayDeque = 3

Getting Size of an ArrayDeque of Strings Example

The following example shows the usage of Java ArrayDeque size() method with Strings. We're creating an ArrayDeque of Strings, adding some elements, print the size and then use remove() method to remove the first element. As ArrayDeque is modified its size is printed again.

package com.tutorialspoint;

import java.util.ArrayDeque;

public class ArrayDequeDemo {
   public static void main(String[] args) {
      
      // create an empty array deque
      ArrayDeque<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 the size of deque
      System.out.println("Size of ArrayDeque = " + deque.size());

      // it will retrieve first element after removing from deque
      deque.remove();
	  
      // let us print the size of deque again
      System.out.println("Size of ArrayDeque = " + deque.size());
   }
}

Output

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

Size of ArrayDeque = 4
Size of ArrayDeque = 3

Getting Size of an ArrayDeque of Objects Example

The following example shows the usage of Java ArrayDeque size() method with Student objects. We're creating an ArrayDeque of Student objects, adding some elements, print the size and then use remove() method to remove the first element. As ArrayDeque is modified its size is printed again.

package com.tutorialspoint;

import java.util.ArrayDeque;

public class ArrayDequeDemo {
   public static void main(String[] args) {
      
      // create an empty array deque
      ArrayDeque<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 the size of deque
      System.out.println("Size of ArrayDeque = " + deque.size());

      // it will retrieve first element after removing from deque
      deque.remove();
	  
      // let us print the size of deque again
      System.out.println("Size of ArrayDeque = " + deque.size());
   }
}
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 −

Size of ArrayDeque = 3
Size of ArrayDeque = 2