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About Byron Kiourtzoglou

Byron Kiourtzoglou
Byron is a master software engineer working in the IT and Telecom domains. He is an applications developer in a wide variety of applications/services. He is currently acting as the team leader and technical architect for a proprietary service creation and integration platform for both the IT and Telecom industries in addition to a in-house big data real-time analytics solution. He is always fascinated by SOA, middleware services and mobile development. Byron is co-founder and Executive Editor at Java Code Geeks.

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.

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