Math - Union of HashSets

Part of the Logic & Flow section of Coddy's Java journey — lesson 29 of 59.

The union of two sets is a new set that contains every element that is in either set. In Java, you can compute the union of two HashSets using the addAll() method. This method adds all elements from one set into another (ignoring duplicates).

First, create a new two HashSets:

HashSet<Integer> set1 = new HashSet<>();
set1.add(1);
set1.add(2);
HashSet<Integer> set2 = new HashSet<>();
set2.add(2);
set2.add(3);

Use the addAll() method to add elements from the second set to your union set.

// First, create a new HashSet with set1
HashSet<Integer> unionSet = new HashSet<>(set1);
unionSet.addAll(set2); // Then, add all elements from set2
System.out.println("Union: " + unionSet);
// Output: [1, 2, 3] (order may vary)

Challenge

Easy

Create a method named <strong>unionSets</strong> that takes two HashSets of integers as input, computes their union, and prints it in the format:

Union: [1, 2, 3]

Cheat sheet

The union of two sets contains every element that is in either set. Use addAll() to compute the union of two HashSets:

HashSet<Integer> set1 = new HashSet<>();
set1.add(1);
set1.add(2);
HashSet<Integer> set2 = new HashSet<>();
set2.add(2);
set2.add(3);

// Create union by copying first set and adding all elements from second
HashSet<Integer> unionSet = new HashSet<>(set1);
unionSet.addAll(set2);
System.out.println("Union: " + unionSet);
// Output: [1, 2, 3] (order may vary)

Try it yourself

import java.util.HashSet;
import java.util.Scanner;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import java.lang.reflect.Type;

public class Main {
    public static void unionSets(HashSet<Integer> set1, HashSet<Integer> set2) {
        // Write your code here
    }
    
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        // Read JSON string representing the first set (e.g., [1,2])
        String set1String = scanner.nextLine();
        // Read JSON string representing the second set (e.g., [2,3])
        String set2String = scanner.nextLine();

        Type setType = new TypeToken<HashSet<Integer>>(){}.getType();
        HashSet<Integer> set1 = new Gson().fromJson(set1String, setType);
        HashSet<Integer> set2 = new Gson().fromJson(set2String, setType);
        
        unionSets(set1, set2);
    }
}