Java Hashmap – containsKey(Object key) and containsValue(Object value) – Check if Key/Value Exists in Map

There are few concepts and technologies which comes by default with each and every programing language and Collection is one of them. Java Collection is a very big field. It comes with so many interfaces and operations.

In this tutorial we will go over Hashmap and two of it’s operation boolean containsKey(Object key) and boolean containsValue(Object value).

Let’s look at below Java code

package com.crunchify.tutorials;

import java.util.HashMap;
import java.util.Map;

/**
 * 
 * @author http://Crunchify.com
 */

public class CrunchifyHashMapContainsKey {
	static Map<String, String> crunchifyComapnies = new HashMap<>();

	private static void checkIfValueExist(String value) {
		// Let's checkout if Value exist
		String result = crunchifyComapnies.containsValue(value) ? ("Value (" + value + ") exist")
				: ("Value (" + value + ") doesn't exist");
		log(result);
	}

	private static void checkIfKeyExist(String key) {
		// Let's checkout if Key exist
		String result = crunchifyComapnies.containsKey(key) ? (crunchifyComapnies.get(key))
				: ("Key (" + key + ") doesn't exist");
		log(result);
	}

	public static void main(String[] args) {

		crunchifyComapnies.put("Google", "Mountain View, CA");
		crunchifyComapnies.put("Yahoo", "Santa Clara, CA");
		crunchifyComapnies.put("Microsoft", "Redmond, WA");

		checkIfKeyExist("Google");
		checkIfKeyExist("Facebook");
		checkIfKeyExist("Twitter");
		checkIfKeyExist("Yahoo");

		System.out.println("\n");
		checkIfValueExist("Mountain View, CA");
		checkIfValueExist("San Jose, CA");
	}

	private static void log(Object object) {
		System.out.println(object);

	}
}

In above tutorial we are using Java’s short if else – ternary operator ?. It’s a shortened version of an if else command.

Here we are adding 3 key,value pairs to map crunchifyCompanies Hashmap. We have created two functions – checkIfKeyExist() and checkIfValueExist(). Those functions will check if key or value exist and calls a log() which prints result on Eclipse console.

Bonus tutorial: Create simple Threadsafe Cache using Hashmap

Output

Mountain View, CA
Key (Facebook) doesn't exist
Key (Twitter) doesn't exist
Santa Clara, CA


Value (Mountain View, CA) exist
Value (San Jose, CA) doesn't exist