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.
