BetAction.java

package com.kyrlach.hello;

public class BetAction {
    private int _amount;
    private Face _face;

    public BetAction(Face face, int amount) {
        _face = face;
        _amount = amount;
    }

    public int getAmount() {
        return _amount;
    }

    public Face getFace() {
        return _face;
    }

    @Override
    public String toString() {
        String faceString = "";
        if(_face.equals(Face.HEADS)) {
            faceString = "heads";
        } else if (_face.equals(Face.TAILS)) {
            faceString = "tails";
        }
        switch(_face) {
            case HEADS:
                faceString = "heads";
                break;
            case TAILS:
                faceString = "tails";
                break;
        }
        return "Betting $" + _amount + " on " + faceString + ".";
    }
}

Face.java

package com.kyrlach.hello;

public enum Face {
    HEADS,
    TAILS,
    UNKNOWN
}

Game.java

package com.kyrlach.hello;

import java.util.Random;

public class Game {
    private final InputOutput _inputOutput;
    private final Player _player;
    private final Random _random;

    public Game(InputOutput inputOutput, Player player) {
        _inputOutput = inputOutput;
        _player = player;
        _random = new Random();
    }

    private Face flip() {
        int rng = _random.nextInt(2) + 1;
        Face result;
        switch(rng) {
            case 1:
                result = Face.HEADS;
                break;
            case 2:
                result = Face.TAILS;
                break;
            default:
                result = Face.UNKNOWN;
        }
        return result;
    }

    private String wagerPrompt() {
        return _player.getName() + ", you have " + _player.getBalance() + ". How much would you like to wager? ";
    }

    private int getWager() {
        boolean done = false;
        int wager = 0;
        while(!done) {
            try {
                String wagerStr = _inputOutput.prompt(wagerPrompt());
                wager = Integer.parseInt(wagerStr);
                if(wager <= _player.getBalance()) {
                    if(wager > 0) {
                        done = true;
                    } else {
                        _inputOutput.println("You have to wager more than " + wager + ".");
                    }
                } else {
                    _inputOutput.println("You don't have that much money to wager!");
                }
            } catch (Exception ex) {
                _inputOutput.println("That doesn't look like a valid bet.");
            }
        }
        return wager;
    }

    private Face getFace() {
        boolean done = false;
        Face face = Face.UNKNOWN;
        while(!done) {
            String faceStr = _inputOutput.prompt("Heads or tails? ");
            if("heads".equals(faceStr)) {
                face = Face.HEADS;
            } else if ("tails".equals(faceStr)) {
                face = Face.TAILS;
            } else {
                _inputOutput.println("I'm not sure what you mean by " + faceStr + ".");
            }
            done = !face.equals(Face.UNKNOWN);
        }
        return face;
    }

    private BetAction getBet() {
        int wager = getWager();
        Face face = getFace();
        return new BetAction(face, wager);
    }

    private boolean donePlaying() {
        boolean done = false;
        boolean result = false;
        while(!done) {
            if(_player.getBalance() <= 0) {
                _inputOutput.println("Looks like you're outta money, kid. Better luck next time!");
                result = true;
                done = true;
            } else {
                String keepPlayingStr = _inputOutput.prompt("You wanna have another go? ");
                if("yes".equals(keepPlayingStr)) {
                    result = false;
                    done = true;
                } else if ("no".equals(keepPlayingStr)) {
                    result = true;
                    done = true;
                } else {
                    _inputOutput.println("I didn't understand you.");
                }
            }
        }
        return result;
    }

    private String faceToString(Face face) {
        String result = "";
        switch(face) {
            case HEADS:
                result = "heads";
                break;
            case TAILS:
                result = "tails";
                break;
        }
        return result;
    }

    public void start() {
        boolean done = false;
        _inputOutput.println("Hello, " + _player.getName() + ".");
        while(!done) {
            BetAction bet = getBet();
            _inputOutput.println(bet.toString());
            _inputOutput.println("Flipping the coin.");
            Face flipResult = flip();
            String flipResultStr = faceToString(flipResult);
            _inputOutput.println("The coin landed on " + flipResultStr + "!");
            if(flipResult.equals(bet.getFace())) {
                _inputOutput.println("Looks like you won... this time!");
                _player.updateBalance(bet.getAmount());
            } else {
                _inputOutput.println("Luck wasn't with you... this time!");
                _player.updateBalance(bet.getAmount() * -1);
            }
            done = donePlaying();
        }
    }

    public static void foo() {

    }
}

InputOutput.java

package com.kyrlach.hello;

import java.io.InputStream;
import java.io.PrintStream;
import java.util.Scanner;

public class InputOutput {
    private Scanner _scanner;
    private PrintStream _out;

    public InputOutput(InputStream in, PrintStream out) {
        _scanner = new Scanner(in);
        _out = out;
    }

    public void println(String message) {
        _out.println(message);
    }

    public void print(String message) {
        _out.print(message);
    }

    public String prompt(String promptText) {
        _out.print(promptText);
        return _scanner.next();
    }

    public void cleanup() {
        _scanner.close();
    }
}
  

Player.java

package com.kyrlach.hello;

public class Player {
    private String _name;
    private int _balance;

    public Player(String name) {
        this(name, 100);
    }

    public Player(String name, int balance) {
        _name = name;
        _balance = balance;
    }

    public String getName() {
        return _name;
    }

    public int getBalance() {
        return _balance;
    }

    public void updateBalance(int delta) {
        _balance += delta;
    }
}

Program.java

package com.kyrlach.hello;

public class Program {
    public static void main(String[] args) {
        InputOutput inputOutput = new InputOutput(System.in, System.out);
        String playerName = inputOutput.prompt("What is your name? ");
        Player player = new Player(playerName);
        Game game = new Game(inputOutput, player);
        game.start();
        inputOutput.println("Goodbye!");
        inputOutput.cleanup();
    }
}