public class Die {

    private static Die die1 = new Die();
    private static Die die2 = new Die();

    /**
     * 私有构造函数保证 外界 无法直接将此类实例化
     */
    private Die() {

    }

/**
     * 工厂方法
     * @param i
     * @return
     */
    public static Die getInstance(int i) {
        switch (i) {
            case 0:
                return die1;
            case 1:
                return die2;
            default:
                return null;
        }
    }

  
/**
     * 掷骰子 返回 1-6 之间的随机数
     * @return int
     */
    public synchronized int dice() {
        System.out.println("-----------------------------");
        Date date = new Date();
        Random random = new Random(date.getTime());
        //random.nextInt()可能返回 负数
        int value = Math.abs(random.nextInt())%6 + 1;
        return value;
    }
}

public class DieTest extends TestCase {

    public void testMain(){
        Die die1 = Die.getInstance(0);
        Die die2 = Die.getInstance(1);
        System.out.println(die1.dice());
        System.out.println(die2.dice());
    }
}