随机枚举返回空

Question

您好，我正在尝试获取随机 ENUM，但它返回 null，有人可以帮助我我的代码有什么问题吗？我试图独自修理它，但我放弃了。

public class LotteryMachine {

    protected enum Sings {

        ONE,

        TWO,

        THREE

}

    private static final List<Sings> SINGS_LIST = Collections.unmodifiableList(Arrays.asList(Sings.values()));

    private static final int SIZE = SINGS_LIST.size();

    private static final Random RANDOM = new Random();

    Sings randomSing() {

        return SINGS_LIST.get(RANDOM.nextInt(SIZE));

    }

}

public class Game {

    private LotteryMachine lotteryMachine = new LotteryMachine();

    private LotteryMachine.Sings singOne;

    private LotteryMachine.Sings singTwo;

    private LotteryMachine.Sings singThree;

    private void Lottery(){

        this.singOne = lotteryMachine.randomSing();

        this.singTwo = lotteryMachine.randomSing();

        this.singThree = lotteryMachine.randomSing();

    }

    public void viewLottery(){

        System.out.print(singOne + " " + singTwo + " " + singThree);

    }

}

Answer 1

你的问题似乎在这里private void Lottery(){&nbsp; &nbsp; this.singOne = lotteryMachine.randomSing();&nbsp; &nbsp; this.singTwo = lotteryMachine.randomSing();&nbsp; &nbsp; this.singThree = lotteryMachine.randomSing();}这不是构造函数；相反，它是一个Lottery()被Game类调用但不使用的私有方法。因为从未调用该方法，所以所有singX字段都未初始化（即为空）。将初始化逻辑从所述方法移动到像这样的字段声明后，事情应该可以正常工作private LotteryMachine.Sings singOne = lotteryMachine.randomSing();private LotteryMachine.Sings singTwo = lotteryMachine.randomSing();private LotteryMachine.Sings singThree = lotteryMachine.randomSing();或者声明Game类的构造函数如下：public Game() {&nbsp; &nbsp; this.singOne = lotteryMachine.randomSing();&nbsp; &nbsp; this.singTwo = lotteryMachine.randomSing();&nbsp; &nbsp; this.singThree = lotteryMachine.randomSing();}