How to Check whether Element Exists in Java ArrayList?

Java ArrayList is a resizable array, which can be found in java.util package. We can add or delete elements from an ArrayList whenever we want, unlike a built-in array.

We can check whether an element exists in ArrayList in java in two ways:

1. Using contains() method
2. Using indexOf() method

Method 1: Using contains() method

The contains() method of the java.util.ArrayList class can be used to check whether an element exists in Java ArrayList.

Syntax:

public boolean contains(Object)

Parameter:

• object – element whose presence in this list is to be tested

Returns: It returns true if the specified element is found in the list else it returns false.

Java

// Java program to check
// whether element exists
// in Java ArrayList

import java.io.*;
import java.util.ArrayList;

class GFG {
    public static void main(String[] args)
    {
        ArrayList<Integer> list = new ArrayList<>();

        // use add() method to add elements in the list
        list.add(1);
        list.add(2);
        list.add(3);
        list.add(4);

        // passing 5 as a
        // parameter to contains()
        // function
        if (list.contains(5))
            System.out.println("5 exists in the ArrayList");

        else
            System.out.println("5 does not exist in the ArrayList");

        if (list.contains(2))
            System.out.println("2 exists in the ArrayList");

        else
            System.out.println("2 does not exist in the ArrayList");

    }
}

Output

5 does not exist in the ArrayList
2 exists in the ArrayList

Method 2: Using indexOf() method

• Contains() method uses indexOf() method to determine if a specified element is present in the list or not. 
• So we can also directly use the indexOf() method to check the existence of any supplied element value.

Java

// Java program to check
// whether element exists
// in Java ArrayList

import java.io.*;
import java.util.ArrayList;

class GFG {
    public static void main (String[] args) {
        ArrayList<Integer> list = new ArrayList<>();

      // use add() method to add elements in the list
      list.add(2);
      list.add(5);
      list.add(1);
      list.add(6);

      // passing 5 as a
      // parameter to contains()
      // function
      if(list.indexOf(5)>=0)
        System.out.println("5 exists in the ArrayList");

      else
        System.out.println("5 does not exist in the ArrayList");

      if(list.indexOf(8)>=0)
         System.out.println("8 exists in the ArrayList");

      else
        System.out.println("8 does not exist in the ArrayList");

    }
}

Output

5 exists in the ArrayList
8 does not exist in the ArrayList