HashMap
Check key existence in HashMap example
With this example we are going to demonstrate how to check a key existence in a HashMap. In short, to check if a key exists in a HashMap you should:
- Create a new HashMap.
- Populate the hashMap with elements, with the
put(K key, V value)
API method of HashMap. - Invoke the
containsKey(Object key)
API method of the HashMap. The method returns true if the HashMap contains the specific key, otherwise it returns false.
Let’s take a look at the code snippet that follows:
package com.javacodegeeks.snippets.core; import java.util.HashMap; public class CheckKeyHashMap { public static void main(String[] args) { // Create a HashMap and populate it with elements HashMap hashMap = new HashMap(); hashMap.put("key_1","value_1"); hashMap.put("key_2","value_2"); hashMap.put("key_3","value_3"); // boolean containsKey(Object key) returns true if the HashMap contains the key, otherwise false. boolean exists = hashMap.containsKey("key_2"); System.out.println("key_2 exists in HashMap ? : " + exists); } }
Output:
key_2 exists in HashMap ? : true
This was an example of how to check a key existence in a HashMap in Java.