add Calc game, rename Game class to Engine, move randomizer to Engine

Author: walpurr

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

@@ -2,6 +2,7 @@
 
 import java.util.Scanner;
 import hexlet.code.games.Even;
+import hexlet.code.games.Calc;
 
 public class App {
     public static void main(String[] args) {
@@ -10,19 +11,16 @@ public static void main(String[] args) {
         System.out.println("Please enter the game number and press Enter.");
         System.out.println("1 - Greet");
         System.out.println("2 - Even");
+        System.out.println("3 - Calc");
         System.out.println("0 - Exit");
         System.out.print("Your choice: ");
         var userChoice = scanner.next();
 
         switch (userChoice) {
-            case "1":
-                Cli.greetUser(scanner);
-                break;
-            case "2":
-                Even.play(scanner);
-                break;
-            default:
-                return;
+            case "1" -> Cli.greetUser(scanner);
+            case "2" -> Even.play(scanner);
+            case "3" -> Calc.play(scanner);
+            default -> scanner.close();
         }
     }
 }

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

@@ -0,0 +1,42 @@
+package hexlet.code.games;
+
+import java.util.Scanner;
+
+public class Calc {
+    public static void play(Scanner scanner) {
+        Engine.greet(scanner);
+
+        while (Engine.isContinuing()) {
+            var number1 = Engine.getRandomNumber(50);
+            var number2 = Engine.getRandomNumber(50);
+            char operator;
+
+            Integer correctAnswer = switch (Engine.getRandomNumber(3)) {
+                case 0 -> {
+                    operator = '+';
+                    yield number1 + number2;
+                }
+                case 1 -> {
+                    operator = '-';
+                    yield number1 - number2;
+                }
+                default -> {
+                    operator = '*';
+                    // balancing difficulty
+                    number2 = number2 / 2;
+                    number1 = number1 / 2;
+                    yield number1 * (number2);
+                }
+            };
+
+            System.out.println("What is the result of the expression?");
+            System.out.println("Question: " + number1 + " " + operator + " " + number2);
+            System.out.print("Your answer: ");
+            var userAnswer = scanner.next();
+
+            Engine.compareAnswers(userAnswer, Integer.toString(correctAnswer));
+        }
+
+        Engine.end(scanner);
+    }
+}

app/src/main/java/hexlet/code/games/Game.java renamed to app/src/main/java/hexlet/code/games/Engine.java

@@ -1,11 +1,13 @@
 package hexlet.code.games;
 
+import java.util.Random;
 import java.util.Scanner;
 
-public class Game {
+public class Engine {
     private static String userName;
     private static boolean defeated = false;
     private static int round = 1;
+    private static Random randomizer = new Random();
 
     public static void greet(Scanner scanner) {
         System.out.println("Welcome to the Brain Games!");
@@ -18,6 +20,10 @@ public static boolean isContinuing() {
         return round <= 3 && !defeated;
     }
 
+    public static int getRandomNumber(int bound) {
+        return randomizer.nextInt(bound);
+    }
+
     public static void compareAnswers(String userAnswer, String correctAnswer) {
         if (userAnswer.equals(correctAnswer)) {
             System.out.println("Correct!");

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

@@ -4,21 +4,21 @@
 
 public class Even {
     public static void play(Scanner scanner) {
-        Game.greet(scanner);
+        Engine.greet(scanner);
 
         System.out.println("Answer 'yes' if the number is even, otherwise answer 'no'.");
 
-        while (Game.isContinuing()) {
-            var randomNumber = Game.getRandomNumber();
+        while (Engine.isContinuing()) {
+            var randomNumber = Engine.getRandomNumber(100) + 1; // added 1 to avoid 0 and keep equal chances
             var correctAnswer = randomNumber % 2 == 0 ? "yes" : "no";
 
             System.out.println("Question: " + randomNumber);
             System.out.print("Your answer: ");
             var userAnswer = scanner.next();
 
-            Game.compareAnswers(userAnswer, correctAnswer);
+            Engine.compareAnswers(userAnswer, correctAnswer);
         }
 
-        Game.end(scanner);
+        Engine.end(scanner);
     }
 }