为什么我的闰年算法不起作用（Java）？ [复制]

这是我所拥有的：

Scanner input = new Scanner(System.in);
    System.out.print("Enter a year: ");
    int Year = input.nextInt();
    System.out.print("Enter a month (first three letters with the first"
            + " letter uppercase): ");
    String Month = input.next();

    String ThirtyOne = "Jan" + "Mar" + "May" + "Jul" + "Aug" + "Oct" + "Dec";
    String DaysThirtyOne = ThirtyOne.substring(21) + "31";

    String Thirty = "Apr" + "Jun" + "Sep" + "Nov";
    String DaysThirty = Thirty.substring(12) + "30";

    String TwentyEight = "Feb";
    String DaysTwentyEight = TwentyEight.substring(3) + "28";
    String DaysLeapYear = TwentyEight.substring(3) + "29";


    boolean isLeapYear = ((Year % 4 == 0) && (Year % 100 != 0) && (Year % 400 == 0));

    if (ThirtyOne.contains(Month)) {
        System.out.println(Month + " " + Year + " has " + DaysThirtyOne 
                + " days in it.");
    }
    if (Thirty.contains(Month)) {
        System.out.println(Month + " " + Year + " has " + DaysThirty 
                + " days in it.");
    }
    if(TwentyEight.contains(Month)) {
        System.out.println(Month + " " + Year + " has " + DaysTwentyEight 
                + " days in it.");
    }
    if (isLeapYear) {
        System.out.println(Month + " " + Year + " has " + DaysLeapYear 
                + " days in it.");
    }

我是编程新手，所以如果这段代码看起来不成熟，我不会感到惊讶。无论如何，我让用户输入一年和一个月（前三个字母）。我为闰年创建了一个布尔变量，表示用户输入的任何年份都需要能被 4、100 和 400 整除。然后，我创建了一个 if 语句来判断是否是闰年，以打印出“二月（无论哪一年）用户输入）中包含 DaysLeapYear。”我认为我的算法有问题，因为如果我取出 TwentyEight 的 if 语句并只保留闰年 if 语句，计算机甚至不会打印出如果是闰年，二月会有多少天。再说一遍，我认为我的算法出了问题，但它可能在其他地方，我希望再看一下这个，看看是否有人看到了我没有看到的东西，因为我毕竟是新手。

首先，您的 isLeapYear 条件需要更改。

boolean isLeapYear = ((Year % 4 == 0) && (Year % 100 != 0) || (Year % 400 == 0));

接下来，您的 if(TwentyEight.contains(Month)) 需要更改以考虑闰年。

if(TwentyEight.contains(Month) && !isLeapYear) {
        System.out.println(Month + " " + Year + " has " + DaysTwentyEight
                + " days in it.");
}