Java TreeMap values() Method

The TreeMap.values() method in Java is used to retrieve a collection view of the values contained in the TreeMap. This guide will cover the method’s usage, explain how it works, and provide examples to demonstrate its functionality. We will also cover a real-world use case to show how TreeMap.values() can be used effectively.

Table of Contents

1. Introduction
2. values Method Syntax
3. Examples
   • Retrieving Values from a TreeMap
   • Iterating Over Values
4. Real-World Use Case
   • Example: Collecting Ages of Contacts
5. Conclusion

Introduction

The TreeMap.values() method is a member of the TreeMap class in Java. It provides a way to retrieve a collection view of the values contained in the TreeMap. This collection is backed by the map, so changes to the map are reflected in the collection, and vice versa.

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<V> view of the values contained in this map.

Examples

Retrieving Values from a TreeMap

The values method can be used to get a collection view of the values in a TreeMap.

Example

import java.util.TreeMap;
import java.util.Collection;

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

        // Adding entries to the TreeMap
        treeMap.put("Ravi", 25);
        treeMap.put("Priya", 30);
        treeMap.put("Vijay", 35);
        treeMap.put("Anita", 28);
        treeMap.put("Suresh", 40);

        // Retrieving the values from the TreeMap
        Collection<Integer> values = treeMap.values();

        // Printing the values
        System.out.println("Values in TreeMap: " + values);
    }
}

Output:

Values in TreeMap: [28, 30, 25, 40, 35]

Iterating Over Values

You can also iterate over the values retrieved from a TreeMap.

Example

import java.util.TreeMap;
import java.util.Collection;

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

        // Adding entries to the TreeMap
        treeMap.put("Ravi", 25);
        treeMap.put("Priya", 30);
        treeMap.put("Vijay", 35);
        treeMap.put("Anita", 28);
        treeMap.put("Suresh", 40);

        // Retrieving the values from the TreeMap
        Collection<Integer> values = treeMap.values();

        // Iterating over the values
        System.out.println("Iterating over values:");
        for (Integer value : values) {
            System.out.println(value);
        }
    }
}

Output:

Iterating over values:
28
30
25
40
35

Real-World Use Case

Example: Collecting Ages of Contacts

A common real-world use case for TreeMap.values() is collecting a list of values (such as ages) from a map of contacts.

Example

import java.util.TreeMap;
import java.util.Collection;

public class ContactManager {
    public static void main(String[] args) {
        // Creating a TreeMap to manage contacts
        TreeMap<String, Integer> contacts = new TreeMap<>();

        // Adding contacts to the TreeMap
        contacts.put("Ravi", 25);
        contacts.put("Priya", 30);
        contacts.put("Vijay", 35);
        contacts.put("Anita", 28);
        contacts.put("Suresh", 40);

        // Retrieving the ages of contacts
        Collection<Integer> ages = contacts.values();

        // Printing the ages
        System.out.println("Ages of contacts: " + ages);
    }
}

Output:

Ages of contacts: [28, 30, 25, 40, 35]

In this example, TreeMap.values() is used to collect the ages of contacts, making it easy to manage and view the list of ages.

Conclusion

The TreeMap.values() method in Java provides a way to retrieve a collection view of the values contained in a TreeMap. By understanding how to use this method, you can efficiently manage collections of values in your Java applications. The method allows you to access and manipulate the values in the map, making it a versatile tool for data management in various scenarios.