Java EnumMap isEmpty() Method

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The EnumMap.isEmpty() method in Java is used to check if the map contains no key-value mappings. This guide will cover the method's usage with examples, and we will also cover a real-world use case to show how EnumMap.isEmpty() can be used effectively.

Table of Contents

1. Introduction
2. isEmpty Method Syntax
3. Examples
   • Basic Usage of isEmpty Method
   • Working with Non-Empty and Empty Maps
4. Real-World Use Case
   • Example: Checking if an EnumMap of Employee Roles is Empty
5. Conclusion

Introduction

The EnumMap.isEmpty() method is a member of the EnumMap class in Java. It returns true if the map contains no key-value mappings, and false otherwise.

isEmpty() Method Syntax

The syntax for the isEmpty method is as follows:

public boolean isEmpty()

• Returns: true if this map contains no key-value mappings, false otherwise.

Examples

Basic Usage of isEmpty Method

The isEmpty method can be used to check if an EnumMap is empty.

Example

import java.util.EnumMap;

public class EnumMapIsEmptyExample {
    // Define an enum representing months of the year
    enum Month {
        JANUARY, FEBRUARY, MARCH, APRIL, MAY, JUNE, JULY, AUGUST, SEPTEMBER, OCTOBER, NOVEMBER, DECEMBER
    }

    public static void main(String[] args) {
        // Create an EnumMap with Month as key and String as value
        EnumMap<Month, String> holidays = new EnumMap<>(Month.class);

        // Checking if the EnumMap is empty initially
        boolean isEmptyInitial = holidays.isEmpty();
        System.out.println("Is the holidays map empty initially? " + isEmptyInitial);

        // Adding entries to the EnumMap
        holidays.put(Month.JANUARY, "New Year's Day");
        holidays.put(Month.DECEMBER, "Christmas Day");

        // Checking if the EnumMap is empty after adding entries
        boolean isEmptyAfterAdding = holidays.isEmpty();
        System.out.println("Is the holidays map empty after adding entries? " + isEmptyAfterAdding);
    }
}

Output:

Is the holidays map empty initially? true
Is the holidays map empty after adding entries? false

Working with Non-Empty and Empty Maps

The isEmpty method returns true for an empty EnumMap and false for a non-empty EnumMap.

Example

import java.util.EnumMap;

public class EnumMapEmptyExample {
    // Define an enum representing types of transportation
    enum Transportation {
        CAR, BUS, TRAIN, AIRPLANE, BICYCLE
    }

    public static void main(String[] args) {
        // Create an empty EnumMap with Transportation as key and Integer as value
        EnumMap<Transportation, Integer> transportMap = new EnumMap<>(Transportation.class);

        // Checking if the EnumMap is empty initially
        boolean isEmptyInitial = transportMap.isEmpty();
        System.out.println("Is the transport map empty initially? " + isEmptyInitial);

        // Adding an entry to the EnumMap
        transportMap.put(Transportation.CAR, 50);

        // Checking if the EnumMap is empty after adding an entry
        boolean isEmptyAfterAdding = transportMap.isEmpty();
        System.out.println("Is the transport map empty after adding an entry? " + isEmptyAfterAdding);

        // Clearing the EnumMap
        transportMap.clear();

        // Checking if the EnumMap is empty after clearing it
        boolean isEmptyAfterClearing = transportMap.isEmpty();
        System.out.println("Is the transport map empty after clearing it? " + isEmptyAfterClearing);
    }
}

Output:

Is the transport map empty initially? true
Is the transport map empty after adding an entry? false
Is the transport map empty after clearing it? true

Real-World Use Case

Example: Checking if an EnumMap of Employee Roles is Empty

A common real-world use case for EnumMap.isEmpty() is checking if a map of employee roles and their associated counts is empty.

Example

import java.util.EnumMap;

public class EmployeeRolesChecker {
    // Define an enum representing employee roles
    enum Role {
        ENGINEER, MANAGER, HR, SALES, MARKETING
    }

    public static void main(String[] args) {
        // Create an EnumMap to manage counts of each employee role
        EnumMap<Role, Integer> employeeRoles = new EnumMap<>(Role.class);

        // Checking if the EnumMap is empty initially
        boolean isEmptyInitial = employeeRoles.isEmpty();
        System.out.println("Is the employee roles map empty initially? " + isEmptyInitial);

        // Adding roles to the EnumMap
        employeeRoles.put(Role.ENGINEER, 5);
        employeeRoles.put(Role.MANAGER, 2);

        // Checking if the EnumMap is empty after adding roles
        boolean isEmptyAfterAdding = employeeRoles.isEmpty();
        System.out.println("Is the employee roles map empty after adding roles? " + isEmptyAfterAdding);
    }
}

Output:

Is the employee roles map empty initially? true
Is the employee roles map empty after adding roles? false

In this example, EnumMap.isEmpty() is used to check if the map of employee roles and their counts is empty, making it easy to verify the presence of role assignments.

Conclusion

The EnumMap.isEmpty() method in Java provides a way to check if the map contains no key-value mappings. By understanding how to use this method, you can efficiently manage and verify the presence of entries in collections where the keys are enum constants. This method allows you to determine if an EnumMap is empty, making it a versatile tool for managing data in various scenarios.