Java ArrayDeque clear() Method

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Description

The Java ArrayDeque clear() method removes all of the elements from this deque. This method is very useful when we want to reuse a queue or reset the queue.

Declaration

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

public void clear()

Parameters

NA

Return Value

This method does not return any value.

Exception

NA

Clearing an ArrayDeque of Integers Example

The following example shows the usage of Java ArrayDeque clear() method. In this example, we're using Integers. As first step, we're populating the arraydeque object and printing it. Then we're print the size of the arraydeque object and perform clear operation. After clearing, we're printing the size of the arraydeque object which is 0 now.

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(20);
      deque.add(30);
      deque.add(10);

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

      // finding size of this deque
      int retval = deque.size();
      System.out.println("Deque consists of "+ retval +" elements");

      System.out.println("Performing clear operation !!");
      deque.clear();
      retval = deque.size();
      System.out.println("Now, deque consists of "+ retval +" elements");
   }
}   

Output

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

ArrayDeque = [20, 30, 10]
Deque consists of 3 elements
Performing clear operation !!
Now, deque consists of 0 elements

Clearing an ArrayDeque of Strings Example

The following example shows the usage of Java ArrayDeque clear() method. In this example, we're using Strings. As first step, we're populating the arraydeque object and printing it. Then we're print the size of the arraydeque object and perform clear operation. After clearing, we're printing the size of the arraydeque object which is 0 now.

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("A");
      deque.add("B");
      deque.add("C");

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

      // finding size of this deque
      int retval = deque.size();
      System.out.println("Deque consists of "+ retval +" elements");

      System.out.println("Performing clear operation !!");
      deque.clear();
      retval = deque.size();
      System.out.println("Now, deque consists of "+ retval +" elements");
   }
}   

Output

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

ArrayDeque = [A, B, C]
Deque consists of 3 elements
Performing clear operation !!
Now, deque consists of 0 elements

Clearing an ArrayDeque of Objects Example

The following example shows the usage of Java ArrayDeque clear() method. In this example, we're using Student objects. As first step, we're populating the arraydeque object and printing it. Then we're print the size of the arraydeque object and perform clear operation. After clearing, we're printing the size of the arraydeque object which is 0 now.

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(1, "Julie"));
      deque.add(new Student(2, "Robert"));
      deque.add(new Student(3, "Adam"));

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

      // finding size of this deque
      int retval = deque.size();
      System.out.println("Deque consists of "+ retval +" elements");

      System.out.println("Performing clear operation !!");
      deque.clear();
      retval = deque.size();
      System.out.println("Now, deque consists of "+ retval +" elements");
   }
} 

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, Julie ], [ 2, Robert ], [ 3, Adam ]]
Deque consists of 3 elements
Performing clear operation !!
Now, deque consists of 0 elements