Java ArrayDeque isEmpty() Method

Description

The Java ArrayDeque isEmpty() method returns true if this deque contains no elements otherwise it returns false.

Declaration

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

public boolean isEmpty()

Parameters

NA

Return Value

This method returns true if this deque contains no elements, else false.

Exception

NA

Checking emptyness of an ArrayDeque of Integers Example

The following example shows the usage of Java ArrayDeque isEmpty() method. Here we are working with an ArrayDeque of Integers. At first, we initialize an ArrayDeque object and then check if it is empty or not. Then we'll be adding few elements and then check again if arraydeque object is empty or not.

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<>();

      if (deque.isEmpty()) {
         System.out.println("deque is empty");
      } else {
         System.out.println("deque is not empty");
      }

      // printing all the elements available in deque
      System.out.println("ArrayDeque = " + deque);

      // use add() method to add elements in the deque
      deque.add(25);
      deque.add(30);
      deque.add(20);
      deque.add(18);        

      if (deque.isEmpty()) {
         System.out.println("deque is empty");
      } else {
         System.out.println("deque is not empty");
      }

      // printing 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 −

deque is empty
ArrayDeque = []
deque is not empty
ArrayDeque = [25, 30, 20, 18]

Checking emptyness of an ArrayDeque of Strings Example

The following example shows the usage of Java ArrayDeque isEmpty() method with an ArrayDeque of Strings. At first, we initialize an ArrayDeque object and then check if it is empty or not. Then we'll be adding few elements and then check again if arraydeque object is empty or not.

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<>();

      if (deque.isEmpty()) {
         System.out.println("deque is empty");
      } else {
         System.out.println("deque is not empty");
      }

      // printing all the elements available in deque
      System.out.println("ArrayDeque = " + deque);

      // use add() method to add elements in the deque
      deque.add("A");
      deque.add("B");
      deque.add("C");
      deque.add("D");        

      if (deque.isEmpty()) {
         System.out.println("deque is empty");
      } else {
         System.out.println("deque is not empty");
      }

      // printing 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 −

deque is empty
ArrayDeque = []
deque is not empty
ArrayDeque = [A, B, C, D]

Checking emptyness of an ArrayDeque of Objects Example

The following example shows the usage of Java ArrayDeque isEmpty() method with an ArrayDeque of Student objects. At first, we initialize an ArrayDeque object and then check if it is empty or not. Then we'll be adding few elements and then check again if arraydeque object is empty or not.

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<>();

      if (deque.isEmpty()) {
         System.out.println("deque is empty");
      } else {
         System.out.println("deque is not empty");
      }

      // printing all the elements available in deque
      System.out.println("ArrayDeque = " + deque);

      // 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"));       

      if (deque.isEmpty()) {
         System.out.println("deque is empty");
      } else {
         System.out.println("deque is not empty");
      }

      // printing 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 + " ]";
   }
   
   @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 −

deque is empty
ArrayDeque = []
deque is not empty
ArrayDeque = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ]]