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:
- Using contains() method
- 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 as as // 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" ); } } |
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 as as // 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" ); } } |
5 exists in the ArrayList 8 does not exist in the ArrayList
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