Java LinkedHashMap isEmpty() Method

The LinkedHashMap.isEmpty() method in Java is used to check if a LinkedHashMap is empty.

Table of Contents

1. Introduction
2. isEmpty Method Syntax
3. Examples
   • Checking if a LinkedHashMap is Empty
4. Real-World Use Case
   • Example: Validating User Session Storage
5. Conclusion

Introduction

The LinkedHashMap.isEmpty() method is a member of the LinkedHashMap class in Java. It allows you to check if the map is empty, meaning it contains no key-value pairs. This can be useful in scenarios where you need to verify if a map is empty before performing certain operations.

isEmpty() Method Syntax

The syntax for the isEmpty method is as follows:

public boolean isEmpty()

• The method does not take any parameters.
• The method returns true if the map contains no key-value mappings, and false otherwise.

Examples

Checking if a LinkedHashMap is Empty

The isEmpty method can be used to check if a LinkedHashMap is empty.

Example

import java.util.LinkedHashMap;

public class IsEmptyExample {
    public static void main(String[] args) {
        // Creating an empty LinkedHashMap with String keys and Integer values
        LinkedHashMap<String, Integer> people = new LinkedHashMap<>();

        // Checking if the LinkedHashMap is empty
        boolean isEmptyBefore = people.isEmpty();

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

        // Checking if the LinkedHashMap is empty after adding entries
        boolean isEmptyAfter = people.isEmpty();

        // Printing the results
        System.out.println("Is LinkedHashMap empty before adding entries? " + isEmptyBefore);
        System.out.println("Is LinkedHashMap empty after adding entries? " + isEmptyAfter);
    }
}

Output:

Is LinkedHashMap empty before adding entries? true
Is LinkedHashMap empty after adding entries? false

Real-World Use Case

Example: Validating User Session Storage

A common real-world use case for LinkedHashMap.isEmpty() is validating if user session storage is empty. For example, let's consider a scenario where we need to check if any user sessions are currently active before performing maintenance operations.

Example

import java.util.LinkedHashMap;

public class SessionManager {
    public static void main(String[] args) {
        // Creating a LinkedHashMap to store user sessions
        LinkedHashMap<String, String> userSessions = new LinkedHashMap<>();

        // Function to check if there are active sessions
        checkActiveSessions(userSessions);

        // Adding some user sessions
        userSessions.put("Ravi", "Session1");
        userSessions.put("Priya", "Session2");

        // Function to check if there are active sessions after adding sessions
        checkActiveSessions(userSessions);

        // Clearing the sessions
        userSessions.clear();

        // Function to check if there are active sessions after clearing sessions
        checkActiveSessions(userSessions);
    }

    public static void checkActiveSessions(LinkedHashMap<String, String> sessions) {
        if (sessions.isEmpty()) {
            System.out.println("No active sessions.");
        } else {
            System.out.println("There are active sessions.");
        }
    }
}

Output:

No active sessions.
There are active sessions.
No active sessions.

In this example, LinkedHashMap.isEmpty() is used to validate if the user session storage is empty, demonstrating how to handle both empty and non-empty states.

Conclusion

The LinkedHashMap.isEmpty() method in Java provides a way to check if a LinkedHashMap is empty. By understanding how to use this method, you can efficiently verify the state of collections of key-value pairs in your Java applications. The method allows you to handle both empty and non-empty maps, making it a versatile tool for data management.