Check If Key Exists

Part of the Logic & Flow section of Coddy's Java journey. Lesson 13 of 59.

The containsKey(key) method checks if a specific key exists in a HashMap. It returns true or false.

For example let's populate a HashMap first:

HashMap<String, Integer> scores = new HashMap<>();
scores.put("Alice", 95);

And now we can check if a key exists:

boolean exists1 = scores.containsKey("Alice");
// exists1 is now true

boolean exists2 = scores.containsKey("Bob");
// exists2 is now false

Challenge

Easy

Create a method named keyChecker that takes two arguments:

A HashMap named randomValues where keys are random strings and values are random values.
An array keys representing string keys.

The method should return the number of keys from keys that exist in the HashMap

Try it yourself

// --- Modules to convert string of hashmap to hashmap ---
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import java.lang.reflect.Type;
// -----------------------------
import java.util.HashMap;
import java.util.Scanner;

public class Main {
    public static int keyChecker(HashMap<String, Integer> randomValues, String[] keys) {
        // Write your code below
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String hashMapString = scanner.nextLine();
        String arrayString = scanner.nextLine();

        // Convert String of HashMap to HashMap
        Type mapType = new TypeToken<HashMap<String, Integer>>(){}.getType();
        HashMap<String, Integer> randomValues = new Gson().fromJson(hashMapString, mapType);

        // Convert String of Array to Array
        String[] keys = new Gson().fromJson(arrayString, String[].class);

        int result = keyChecker(randomValues, keys);
        System.out.println(result);
    }
}