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ArrayList contains() method in Java

In this article, we will see the contains() method of ArrayList class in Java. This method is used to check if the list contains the element.

Introduction

ArrayList is an ordered collection and it allows duplicate elements. It is widely used to store and retrieve data.

We have seen a few methods of the ArrayList class before like add(), addAll(), remove(), set(), iterate() and clear(). Today we will see the contains() method.

If we need to check if any element is present in the list or not, we can use the contains() method from the ArrayList class in Java.

ArrayList contains() method

It has a method signature as given below.

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public boolean contains(Object o)

This method is used to check if the ArrayList contains the specified element.

This method accepts a single parameter of type Object

  • o: - an Object o whose presence in this list is to be tested

This method has a return type as a boolean. It returns true if the list contains the specified element. Otherwise, it returns false.

I have given a Java program to check if the list contains the specified element using the ArrayList contains() method.

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import java.util.ArrayList;
import java.util.List;
/**
 * A Java program to check if the ArrayList 
 * contains the specified element.
 * 
 * @author coderolls.com
 *
 */
public class ArrayListContainsMethodExample {

  public static void main(String[] args) {
  
    //create an empty ArrayList object 'states'
    List<String> states = new ArrayList<String>();
    
    //add state in the ArrayList 
    states.add("California");
    states.add("Texas");
    states.add("Florida");
    states.add("New Jersey");
    states.add("Washington");
    
    //check if states contain Florida
    boolean isPresent1 = states.contains("Florida");
    System.out.println("Is Florida present in the list: "+ isPresent1);
    
    //check if states contain Alaska
    boolean isPresent2 =states.contains("Alaska");
    System.out.println("\nIs Alaska present in the list: "+ isPresent2);
  }
}

Output:

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Is Florida present in the list: true

Is Alaska present in the list: false

Explanation

  1. I have created an ArrayList object states.
  2. I have added a few String objects in the states.
  3. I have checked if the list states contains the Florida string object using the contains() method. Since Florida is present in the states list, it returns true.
  4. I have captured the return value for the first contains() method in the isPresent1 boolean variable. When we print the isPresent1, it has a value true.
  5. Next time, I checked if the states list contains the Alaska using the contains() method. Since Alaska is not present in the states list, it returns false
  6. I have captured the return value for the second contains() method in the isPresent2 boolean variable. When we print the isPresent2, it has a value false.

Conclusion

The ArrayList contains() method is used to check if the list contains the specified element.

This method returns true if the specified element is present in the list. Otherwise, it returns false

The example Java program used in the above article can be found at this GitHub repository.

If you know anything other than this, kindly write in the comment section below.

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