package game;

import game.TimeCounter;
import game.exercise.Examiner;

public class Game {
    public static void main(String[] args) {
        System.out.println("You have to solve as many exercises as you can " +
        "within 20 seconds");
        Examiner examiner = new Examiner();
        examiner.start();
        TimeCounter timeCounter = new TimeCounter(examiner, 20);
        timeCounter.countTimeAndInterrupt();
        examiner.printStats();
    }
}

package game;

import game.exercise.Examiner;

public class TimeCounter {
    private Examiner examiner;
    private int seconds;

    public TimeCounter(Examiner examiner, int seconds) {
        this.examiner = examiner;
        this.seconds = seconds;
    }



    public void countTimeAndInterrupt() {
        for(int i = 0; i < seconds; i++) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        examiner.stop();
    }
}

package game.exercise;

import java.util.Scanner;

public class Examiner extends Thread {
    private int right; // number of exercises solved right
    private int wrong;

    @Override
    public void run() {
        Scanner scanner = new Scanner(System.in);

        while (true) {
            int input;
            Exercise exercise;

            exercise = Exercise.getRandomExercise();
            System.out.print(exercise);
            input = scanner.nextInt();
            if (exercise.check(input)) {
                right++;
                System.out.println("Right!");

            } else {
                wrong++;
                System.out.println("Wrong!");
            }
        }
    }

    public void printStats() {
        System.out.println();
        System.out.println("Number of all exercises: " +
        getNumberOfExercises());
        System.out.println("Exercises solved right: " + right);
        System.out.println("Exercises solved wrong: " + wrong);
        int percentage = (int)((float)(right) / getNumberOfExercises() * 100);
        System.out.println("Rate: " + percentage + " % ");
    }

    public int getNumberOfExercises() {
        return right + wrong;
    }
}

package game.exercise;

import java.util.Random;

public class Exercise {
    private static Random random = new Random();
    private int number1;
    private int number2;
    private Type type;

    public Exercise(Type type, int number1, int number2) {
        this.type = type;
        this.number1 = number1;
        this.number2 = number2;
    }

    public static Exercise getRandomExercise() {
        return getRandomExercise(Type.random());
    }

    public static Exercise getRandomExercise(Type type) {
        switch(type) {
            case ADDITION:
            case SUBTRACTION:
                return new Exercise(type, random.nextInt(40) + 1,
                random.nextInt(40) + 1);
            case MULTIPLICATION:
                return new Exercise(type, random.nextInt(20) + 1,
                random.nextInt(20) + 1);
            case DIVISION:
                return new Exercise(type, random.nextInt(100) + 1,
                random.nextInt(15) + 1);
            default: throw new IllegalArgumentException("not a valid type");
        }
    }

    @Override
    public String toString() {
        return number1 + " " + getOperator() + " " + number2 + " = ";
    }

    private String getOperator() {
        switch(type) {
            case ADDITION: return "+";
            case SUBTRACTION: return "-";
            case MULTIPLICATION: return "*";
            case DIVISION: return "/";
            default: throw new IllegalArgumentException("not a valid type");
        }
    }

    private int getSolution() {
        switch(type) {
            case ADDITION: return number1 + number2;
            case SUBTRACTION: return number1 - number2;
            case MULTIPLICATION: return number1 * number2;
            case DIVISION: return (int)(number1 / number2);
            default: throw new IllegalArgumentException("not a valid type");
        }
    }

    public boolean check(int guess) {
        return getSolution() == guess;
    }
}

package game.exercise;

import java.util.Random;

public enum Type {
    ADDITION, SUBTRACTION, MULTIPLICATION, DIVISION;

    public static Type random() {
        Random random = new Random();
        int choice = random.nextInt(4);
        if(choice == 0) return ADDITION;
        else if(choice == 1) return SUBTRACTION;
        else if(choice == 2) return MULTIPLICATION;
        else if(choice == 3) return DIVISION;
        else throw new IllegalArgumentException();
    }
}