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, explain how it works, and provide examples to demonstrate its functionality using different enum constants as keys. We will also cover a real-world use case to show how EnumMap.isEmpty()
can be used effectively.
Table of Contents
- Introduction
isEmpty
Method Syntax- Examples
- Basic Usage of
isEmpty
Method - Working with Non-Empty and Empty Maps
- Basic Usage of
- Real-World Use Case
- Example: Checking if an EnumMap of Employee Roles is Empty
- 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.