Lösungsvorschlag: Münzenspiel

import java.util.Scanner;
 
/**
 * play a game with coins
 * 
 * @author Marcel Suter
 * @since 2018-09-28
 * @version 1.0
 */
public class CoinGame{
 
    static Scanner scanner;
 
    /**
     * constructor
     */
    public CoinGame() {
        scanner = new Scanner(System.in);
    }
 
    /**
     * starts the execution
     * 
     * @param args
     *            command line arguments
     */
    public static void main(String[] args) {
        CoinGame program = new CoinGame();
 
        System.out.println("Willkommen zum Münzenspiel");
        program.play();
        System.out.println("Bis bald!");
        scanner.close();
    }
 
    /**
     * play the coin game
     */
    private void play() {
        int coinRest;
        int coinTake;
        byte player = 1;
 
        coinRest = (int)(Math.random() * 20 + 10);  // generates a random number of coins
 
        while (coinRest > 0) {
            System.out.println("Es sind noch " + coinRest + " Münzen auf dem Stapel");
            System.out.print("Spieler " + player + " nimm 1-3 Münzen >") ;
            coinTake = scanner.nextShort();
 
            if (coinTake < 1) {
                System.out.println("Du musst mindestens 1 Münze nehmen");
            } else {
                if (coinTake > 3) {
                    System.out.println("Du kannst höchstens 3 Münzen nehmen");
                } else {
                    coinRest = coinRest - coinTake;
                    player = (byte) (3 - player);
                    System.out.println("");
                }
            }
        }
        System.out.println("Spieler " + player + " hat verloren");
    }
}