Java HashMap values() Method

The HashMap.values() method in Java is used to retrieve a collection view of the values contained in the HashMap. This guide will cover the method's usage, explain how it works, and provide examples to demonstrate its functionality.

Table of Contents

1. Introduction
2. values Method Syntax
3. Examples
   • Iterating Over Values in a HashMap
   • Real-World Use Case: Calculating the Average Age
4. Conclusion

Introduction

The HashMap.values() method is a member of the HashMap class in Java. It provides a collection view of the values contained in the HashMap. This can be useful for operations that need to process or analyze the values without concerning the keys.

values() Method Syntax

The syntax for the values method is as follows:

public Collection<V> values()

• The method does not take any parameters.
• The method returns a Collection view of the values in the HashMap.

Examples

Iterating Over Values in a HashMap

The values method can be used to retrieve a collection of the values in a HashMap, which can then be iterated over.

Example

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

public class ValuesExample {
    public static void main(String[] args) {
        // Creating a HashMap with String keys and Integer values
        HashMap<String, Integer> people = new HashMap<>();

        // Adding entries to the HashMap
        people.put("Ravi", 25);
        people.put("Priya", 30);
        people.put("Vijay", 35);

        // Getting the collection of values
        Collection<Integer> values = people.values();

        // Iterating over the values
        values.forEach(value -> System.out.println("Value: " + value));
    }
}

Output:

Value: 25
Value: 30
Value: 35

Real-World Use Case: Calculating the Average Age

In a real-world scenario, you might use the values method to retrieve all values from a HashMap and perform calculations such as finding the average age of people in a list.

Example

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

public class AverageAgeCalculator {
    public static void main(String[] args) {
        // Creating a HashMap with String keys and Integer values
        HashMap<String, Integer> people = new HashMap<>();

        // Adding entries to the HashMap
        people.put("Ravi", 25);
        people.put("Priya", 30);
        people.put("Vijay", 35);

        // Getting the collection of values
        Collection<Integer> values = people.values();

        // Calculating the average age
        double averageAge = values.stream().mapToInt(Integer::intValue).average().orElse(0);

        // Printing the average age
        System.out.println("Average Age: " + averageAge);
    }
}

Output:

Average Age: 30.0

Conclusion

The HashMap.values() method in Java provides a way to retrieve a collection view of the values contained in the HashMap. By understanding how to use this method, you can efficiently access and process the values in your map. This method is useful in various scenarios, such as iterating over values, performing calculations, and analyzing data stored in a HashMap. Using lambda expressions and streams with this method makes the code more concise and readable.