Math - Intersection of HashSet

Part of the Logic & Flow section of Coddy's Java journey — lesson 30 of 59.

The intersection of two sets is a new set that contains only the elements that are present in both sets. In Java, you can compute the intersection by using the retainAll() method.

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);

This new set will start with all elements from the first set.

HashSet<Integer> intersectionSet = new HashSet<>(set1);

Next, retain only the elements that are also in the second set:
Use the retainAll() method.

intersectionSet.retainAll(set2);
System.out.println("Intersection: " +
						intersectionSet);
// Output: [2]

Challenge

Easy

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

Intersection: [2]

Cheat sheet

The intersection of two sets contains only elements present in both sets. Use retainAll() to compute intersection:

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

// Create new set with elements from first set
HashSet<Integer> intersectionSet = new HashSet<>(set1);

// Retain only elements that are also in second set
intersectionSet.retainAll(set2);
System.out.println("Intersection: " + intersectionSet);
// Output: [2]

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 intersectionSets(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 for the first set (e.g., [1,2])
        String set1String = scanner.nextLine();
        // Read JSON string for 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);
        
        intersectionSets(set1, set2);
    }
}