add GCD game

Author: walpurr

app/src/main/java/hexlet/code/App.java

@@ -3,6 +3,7 @@
 import java.util.Scanner;
 import hexlet.code.games.Even;
 import hexlet.code.games.Calc;
+import hexlet.code.games.GCD;
 
 public class App {
     public static void main(String[] args) {
@@ -12,6 +13,7 @@ public static void main(String[] args) {
         System.out.println("1 - Greet");
         System.out.println("2 - Even");
         System.out.println("3 - Calc");
+        System.out.println("4 - GCD");
         System.out.println("0 - Exit");
         System.out.print("Your choice: ");
         var userChoice = scanner.next();
@@ -20,6 +22,7 @@ public static void main(String[] args) {
             case "1" -> Cli.greetUser(scanner);
             case "2" -> Even.play(scanner);
             case "3" -> Calc.play(scanner);
+            case "4" -> GCD.play(scanner);
             default -> scanner.close();
         }
     }

app/src/main/java/hexlet/code/games/Even.java

@@ -9,7 +9,7 @@ public static void play(Scanner scanner) {
         System.out.println("Answer 'yes' if the number is even, otherwise answer 'no'.");
 
         while (Engine.isContinuing()) {
-            var randomNumber = Engine.getRandomNumber(100) + 1; // added 1 to avoid 0 and keep equal chances
+            var randomNumber = Engine.getRandomNumber(100) + 1; // added 1 to avoid 0
             var correctAnswer = randomNumber % 2 == 0 ? "yes" : "no";
 
             System.out.println("Question: " + randomNumber);

app/src/main/java/hexlet/code/games/GCD.java

@@ -0,0 +1,28 @@
+package hexlet.code.games;
+
+import java.util.Scanner;
+
+public class GCD {
+    public static int getGCD(int a, int b) {
+        return (a % b == 0) ? Math.abs(b) : getGCD(b, a % b);
+    }
+
+    public static void play(Scanner scanner) {
+        Engine.greet(scanner);
+
+        while (Engine.isContinuing()) {
+            var number1 = Engine.getRandomNumber(100) + 1; // added 1 to avoid 0
+            var number2 = Engine.getRandomNumber(100) + 1;
+            int correctAnswer = getGCD(number1, number2);
+
+            System.out.println("Find the greatest common divisor of given numbers.");
+            System.out.println("Question: " + number1 + " " + number2);
+            System.out.print("Your answer: ");
+            var userAnswer = scanner.next();
+
+            Engine.compareAnswers(userAnswer, Integer.toString(correctAnswer));
+        }
+
+        Engine.end(scanner);
+    }
+}