Java HashMap containsValue() usage and example

Java HashMap Methods

The Java HashMap containsValue() method checks if the specified value exists in one or more mappings in the hash map.

The syntax of the containsValue() method is:

hashmap.containsValue(Object value)

containsValue() parameter

• value- The value exists in one or more mappings in the HashMap
  

containsValue() returns value

• If the specified value exists, it returns true
  

• If the specified value does not exist, it returns false

Example1: Java HashMap containsValue()

import java.util.HashMap;
class Main {
　　public static void main(String[] args){
　　　　//　Create HashMap
　　　　HashMap<Integer, String> languages = new HashMap<>();
　　　　//Add the mapping to the HashMap
　　　　languages.put(1, "Python");
　　　　languages.put(2, "Java");
　　　　languages.put(3, "JS");
　　　　System.out.println("HashMap"　+　languages);
　　　　//Check if the value Java exists
　　　　if(languages.containsValue("Java")) {
　　　　　　System.out.println("Java exists in the list.");
　　　　}
　　}
}

Output Result

HashMap{1=Python,　2=Java,　3=JS}
Java exists in the list.

In the above example, we created a hash map named languages. Note these expressions,

languages.containsValue("Java")　//　Returns true

Here, the specified value Java exists in the mapping ({2 = Java} Therefore, the if code block is executed, and the containsValue() method will return true and the statement.

Example2: If the value does not exist yet, add the entry to the HashMap

import java.util.HashMap;
class Main {
　　public static void main(String[] args){
　　　　//　Create HashMap
　　　　HashMap<String, String> countries = new HashMap<>();
　　　　//Add the mapping to the HashMap
　　　　countries.put("Washington", "USA");
　　　　countries.put("Canberra", "Australia");
　　　　System.out.println("HashMap:\n"　+　countries);
　　　　//Check if the value Spain exists
　　　　if(!countries.containsValue("Spain")) {
　　　　　　//If the value does not exist, add the entry
　　　　　　countries.put("Madrid", "Spain");
　　　　}
　　　　System.out.println("Updated HashMap:\n"　+　countries);
　　}
}

Output Result

HashMap:
{Canberra=Australia, Washington=USA}
Updated HashMap:
{Madrid=Spain, Canberra=Australia, Washington=USA}

In the above example, please note the following expression:

if(!countries.containsValue("Spain"))　{..}

Here, we used the containsValue() method to check if the specified value Spain exists in the hash map. Since we used the negation symbol (!), if this method returns false, the if block will be executed

Therefore, a new mapping is only added if there is no existing mapping for the specified value in the hash map.

Note: We can also useHashMap putIfAbsent()Methods perform the same task.

Java HashMap Methods