Java EnumSet containsAll() Method

The EnumSet.containsAll() method in Java is used to check if the EnumSet contains all elements of a specified collection. This guide will cover the method's usage with examples, and we will also cover a real-world use case to show how EnumSet.containsAll() can be used effectively.

Table of Contents

1. Introduction
2. containsAll Method Syntax
3. Examples
   • Basic Usage of containsAll Method
   • Checking for All Elements in a Collection
4. Real-World Use Case
   • Example: Verifying Selected Days of the Week
5. Conclusion

Introduction

The EnumSet.containsAll() method is a member of the EnumSet class in Java. It allows you to check if the EnumSet contains all elements of a specified collection. The method returns true if all elements are present, and false otherwise.

containsAll() Method Syntax

The syntax for the containsAll method is as follows:

public boolean containsAll(Collection<?> c)

• Parameters:
  • c: The collection to be checked for containment in this set.
• Returns: true if this set contains all of the elements in the specified collection.

Examples

Basic Usage of containsAll Method

The containsAll method can be used to check if the EnumSet contains all elements of a specified collection.

Example

import java.util.EnumSet;
import java.util.ArrayList;
import java.util.List;

public class EnumSetContainsAllExample {
    // Define an enum representing days of the week
    enum Day {
        MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY
    }

    public static void main(String[] args) {
        // Creating an EnumSet with specific elements
        EnumSet<Day> days = EnumSet.of(Day.MONDAY, Day.WEDNESDAY, Day.FRIDAY);

        // Creating a list of days to check
        List<Day> daysToCheck = new ArrayList<>();
        daysToCheck.add(Day.MONDAY);
        daysToCheck.add(Day.WEDNESDAY);

        // Checking if the EnumSet contains all elements of the list
        boolean containsAll = days.containsAll(daysToCheck);

        // Printing the result
        System.out.println("EnumSet contains all elements of the list: " + containsAll);
    }
}

Output:

EnumSet contains all elements of the list: true

Checking for All Elements in a Collection

You can use the containsAll method to check if the EnumSet contains all elements of various collections.

Example

import java.util.EnumSet;
import java.util.ArrayList;
import java.util.List;

public class EnumSetContainsAllMultipleExample {
    // Define an enum representing types of fruits
    enum Fruit {
        APPLE, BANANA, ORANGE, MANGO, GRAPE
    }

    public static void main(String[] args) {
        // Creating an EnumSet with specific elements
        EnumSet<Fruit> fruits = EnumSet.of(Fruit.APPLE, Fruit.BANANA, Fruit.ORANGE);

        // Creating a list of fruits to check
        List<Fruit> fruitsToCheck1 = new ArrayList<>();
        fruitsToCheck1.add(Fruit.APPLE);
        fruitsToCheck1.add(Fruit.BANANA);

        // Creating another list of fruits to check
        List<Fruit> fruitsToCheck2 = new ArrayList<>();
        fruitsToCheck2.add(Fruit.MANGO);
        fruitsToCheck2.add(Fruit.GRAPE);

        // Checking if the EnumSet contains all elements of the first list
        boolean containsAll1 = fruits.containsAll(fruitsToCheck1);
        System.out.println("EnumSet contains all elements of the first list: " + containsAll1);

        // Checking if the EnumSet contains all elements of the second list
        boolean containsAll2 = fruits.containsAll(fruitsToCheck2);
        System.out.println("EnumSet contains all elements of the second list: " + containsAll2);
    }
}

Output:

EnumSet contains all elements of the first list: true
EnumSet contains all elements of the second list: false

Real-World Use Case

Example: Verifying Selected Days of the Week

A common real-world use case for EnumSet.containsAll() is verifying if a set of selected days contains all required days for a specific schedule.

Example

import java.util.EnumSet;
import java.util.ArrayList;
import java.util.List;

public class SelectedDaysVerifier {
    // Define an enum representing days of the week
    enum Day {
        MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY
    }

    public static void main(String[] args) {
        // Creating an EnumSet with selected days
        EnumSet<Day> selectedDays = EnumSet.of(Day.MONDAY, Day.WEDNESDAY, Day.FRIDAY);

        // Creating a list of required days for a specific schedule
        List<Day> requiredDays = new ArrayList<>();
        requiredDays.add(Day.MONDAY);
        requiredDays.add(Day.FRIDAY);

        // Checking if the selected days contain all required days
        boolean containsAllRequiredDays = selectedDays.containsAll(requiredDays);

        // Printing the result
        System.out.println("Selected days contain all required days: " + containsAllRequiredDays);
    }
}

Output:

Selected days contain all required days: true

In this example, EnumSet.containsAll() is used to verify if a set of selected days contains all required days for a specific schedule, making it easy to manage and verify schedules.

Conclusion

The EnumSet.containsAll() method in Java provides a way to check if the EnumSet contains all elements of a specified collection. By understanding how to use this method, you can efficiently manage and verify collections of enum constants. This method allows you to utilize the power of EnumSet for various scenarios, making it a versatile tool for managing collections of enum constants.