Java ArrayDeque removeFirstOccurrence() Method with Examples

Description

The Java ArrayDeque removeFirstOccurrence(Object) method removes the first occurrence of the specified element in this deque. This operation modifies the ArrayDeque instance.

Declaration

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

public boolean removeFirstOccurrence(Object o)

Parameters

o − The element whose first occurrence is to be removed from this deque, if present.

Return Value

This method returns true if the deque contains the specified element.

Exception

NA

Example #1

The following example shows the usage of Java ArrayDeque removeFirstOccurrence() method with Integers. We're creating an ArrayDeque of Integers, adding some elements, print it and then use removeFirstOccurrence() method to remove first occurence of an element. As ArrayDeque is modified it is printed to check if first occurence of that element is removed or not.

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);  
      deque.add(20);      

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

      // it will remove first occurrence of element
      System.out.println("Element removed : " + deque.removeFirstOccurrence(20));
	  
      // let us print all the elements available in deque again
      System.out.println("ArrayDeque = " + deque);
   }
}

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

ArrayDeque = [25, 30, 20, 18, 20]
Element removed : true
ArrayDeque = [25, 30, 18, 20]

Example #2

The following example shows the usage of Java ArrayDeque removeFirstOccurrence() method with Strings. We're creating an ArrayDeque of Strings, adding some elements, print it and then use removeFirstOccurrence() method to remove first occurence of an element. As ArrayDeque is modified it is printed to check if first occurence of that element is removed or not.

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

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

      // it will remove first occurrence of element
      System.out.println("Element removed : " + deque.removeFirstOccurrence("C"));
	  
      // let us print all the elements available in deque again
      System.out.println("ArrayDeque = " + deque);
   }
}

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

ArrayDeque = [A, B, C, D, C]
Element removed : true
ArrayDeque = [A, B, D, C]

Example #3

The following example shows the usage of Java ArrayDeque removeFirstOccurrence() method with Student objects. We're creating an ArrayDeque of Student objects, adding some elements, print it and then use removeFirstOccurrence() method to remove first occurence of an element. As ArrayDeque is modified it is printed to check if first occurence of that element is removed or not.

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"));       
      deque.add(new Student(2, "Robert"));
	  
      // let us print all the elements available in deque
      System.out.println("ArrayDeque = " + deque);

      // it will remove first occurrence of element
      System.out.println("Element removed : " + deque.removeFirstOccurrence(new Student(2, "Robert")));
	  
      // let us print all the elements available in deque again
      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);
   }
}

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

ArrayDeque = [[ 1, Julie ], [ 2, Robert ], [ 3, Adam ], [ 2, Robert ]]
Element removed : true
ArrayDeque = [[ 1, Julie ], [ 3, Adam ], [ 2, Robert ]]