How to Perform Union and Intersection of Sets in Java

What is the simplest way to perform union and intersection operations on Sets in Java?

In Java, the Set interface provides a straightforward way to manage collections of unique elements. When it comes to performing union and intersection operations on Sets, Java offers several methods, leveraging the power of the Collections framework for convenience and performance.

import java.util.HashSet;
import java.util.Set;

public class SetOperations {
    public static void main(String[] args) {
        Set<Integer> setA = new HashSet<>();
        Set<Integer> setB = new HashSet<>();

        // Adding elements to set A
        setA.add(1);
        setA.add(2);
        setA.add(3);

        // Adding elements to set B
        setB.add(2);
        setB.add(3);
        setB.add(4);

        // Union of set A and set B
        Set<Integer> unionSet = new HashSet<>(setA);
        unionSet.addAll(setB);
        System.out.println("Union: " + unionSet);

        // Intersection of set A and set B
        Set<Integer> intersectionSet = new HashSet<>(setA);
        intersectionSet.retainAll(setB);
        System.out.println("Intersection: " + intersectionSet);
    }
}

Causes

• Confusion due to manual iteration methods for union and intersection tasks.
• Lack of understanding of Collections framework utilities.

Solutions

• Use the addAll() method for union operations.
• Use the retainAll() method for intersection operations.
• Utilize Java Streams for a functional approach.

Mistake: Not using the appropriate Set implementation for the task.

Solution: Choose HashSet for performance or TreeSet for sorted order.

Mistake: Overcomplicating union and intersection with manual loops.

Solution: Utilize built-in set methods like addAll() and retainAll().