Java – Get all values in HashMap using values()

Java HashMap.values()

In this tutorial, we will learn about the Java HashMap.values() function, and learn how to use this function to get all the values in this HashMap as a Collection, with the help of examples.

values()

HashMap.values() returns a values contained in this HashMap as a Collection.

The syntax of values() function is

values()

Returns

The function returns Collection of values.

Examples

1. values() basic example

In this example, we will initialize a HashMap hashMap with four mappings in it. To get all the values in this collection, call values() method on this HashMap.

Java Program

import java.util.Collection;
import java.util.HashMap;

public class Example{ 
	public static void main(String[] args) {
		HashMap<Integer, String> hashMap = new HashMap<>();
		hashMap.put(1, "A");
		hashMap.put(2, "B");
		hashMap.put(3, "C");
		hashMap.put(4, "D");
		System.out.println("HashMap  : " + hashMap);
		
		Collection<String> values = hashMap.values();
		System.out.println("Values   : " + values);
	}
}

Output

HashMap  : {1=A, 2=B, 3=C, 4=D}
Values   : [A, B, C, D]

2. values() – When HashMap is null

In this example, we will initialize a HashMap hashMap with null value. values() method throws java.lang.NullPointerException when called on a null HashMap.

Java Program

import java.util.Collection;
import java.util.HashMap;

public class Example{ 
	public static void main(String[] args) {
		HashMap<Integer, String> hashMap = null;
		
		Collection<String> values = hashMap.values();
		System.out.println("Values   : " + values);
	}
}

Output

Exception in thread "main" java.lang.NullPointerException
	at Example.main(Example.java:8)

Conclusion

In this Java Tutorial, we have learnt the syntax of Java HashMap.values() function, and also learnt how to use this function with the help of examples.