Java – Check if a particular key exists in HashMap example

In the last tutorial we learnt how to check whether a particular value exists in HashMap. In this example we are gonna see how to check if a particular key is present in HashMap. We will be using containsKey() method of HashMap class to perform this check. The method definition and description are as follows:

public boolean containsKey(Object key): Returns true if this map contains a mapping for the specified key.

Example

The steps we followed in the below example are:

1) Create a HashMap and populate it with key-value pairs.
2) Check any key existence by calling containsKey() method. This method returns a boolean value.

import java.util.HashMap;

public class CheckKeyExample {
 
 public static void main(String[] args) {
 
    // Creating a HashMap of int keys and String values
    HashMap<Integer, String> hashmap = new HashMap<Integer, String>();
 
    // Adding Key and Value pairs to HashMap
    hashmap.put(11,"Chaitanya");
    hashmap.put(22,"Pratap");
    hashmap.put(33,"Singh");
    hashmap.put(44,"Rajesh");
    hashmap.put(55,"Kate");
 
    // Checking Key Existence
    boolean flag = hashmap.containsKey(22);
    System.out.println("Key 22 exists in HashMap? : " + flag);
 
    boolean flag2 = hashmap.containsKey(55);
    System.out.println("Key 55 exists in HashMap? : " + flag2);
 
    boolean flag3 = hashmap.containsKey(99);
    System.out.println("Key 99 exists in HashMap? : " + flag3);
 }
}

Output:

Key 22 exists in HashMap? : true
Key 55 exists in HashMap? : true
Key 99 exists in HashMap? : false