双色球-实现机选功能

最近老大给我们出了一道题，要求纯文本编程......
要求：实现双色球机选N注
下面是大牛版的代码：反正我是比较推崇，仅供参考。

import java.awt.Color;
import java.util.Random;
import java.util.List;
import java.util.ArrayList;
import java.util.Arrays;

class Ball implements Comparable<Ball> {
    private int number;
    private Color color;

    public Ball(int number, Color color) {
        this.number = number;
        this.color = color;
    }

    public int getNumber() {
        return number;
    }

    public Color getColor() {
        return color;
    }

    @Override
    public int compareTo(Ball other) {
        return this.number - other.number;
    }
}

class SelectNumberMachine {
    private static Random r = new Random();
    private List<Ball> redBalls = new ArrayList<>();
    private List<Ball> blueBalls = new ArrayList<>();

    public void reset() {
        redBalls.clear();
        for (int i = 1; i <= 33; ++i) {
            redBalls.add(new Ball(i, Color.RED));
        }
        blueBalls.clear();
        for (int i = 1; i <= 16; ++i) {
            blueBalls.add(new Ball(i, Color.BLUE));
        }
    }

    public String generate() {
        Ball[] currentRedBalls = selectRedBalls();
        Arrays.sort(currentRedBalls);
        Ball currentBlueBall = selectBlueBall();
        StringBuilder sb = new StringBuilder();
        for (Ball tempBall : currentRedBalls) {
            sb.append(String.format("%02d ", tempBall.getNumber()));
        }
        sb.append("| ");
        sb.append(String.format("%02d", currentBlueBall.getNumber()));
        return sb.toString();
    }

    private Ball[] selectRedBalls() {
        Ball[] currentRedBalls = new Ball[6];
        for (int i = 0; i < currentRedBalls.length; ++i) {
            int randomIndex = r.nextInt(redBalls.size());
            currentRedBalls[i] = redBalls.remove(randomIndex);
        }
        return currentRedBalls;
    }

    private Ball selectBlueBall() {
        int randomIndex = r.nextInt(blueBalls.size());
        return blueBalls.remove(randomIndex);
    }

}

class Test {

    public static void main(String[] args) {
        SelectNumberMachine machine = new SelectNumberMachine();
        for (int i = 0; i < 10; ++i) {
            machine.reset();
            System.out.println(machine.generate());
        }
    }
}