Question

我正在为类编写程序，循环似乎无法正确执行。它始终将i的值返回为 0 。其余的代码看起来像宣传的那样工作，i只是没有增加索引值。

public class Day {
    String strDay;
    private int d = 0;
    private String[] Days = {"SUNDAY", "MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY", "SATURDAY"};
    String day;

    public Day() {
        return;
    }

    public Day(String strDay) {// this is my issue. I think I am going about this constructor all wrong
        for (int i = 0; i < Days.length; i++) {
            if (strDay.equalsIgnoreCase(Days[i]))
                d = i;
            return;
        }
    }

    public int getDay() {
        return d;
    }

    public void nexDay() {
        int next;
        if (d < 6) {
            next = (this.d) + 1;
            System.out.println("Next Day is :" + Days[next]);
        } else {
            next = 0;
            System.out.println("Next Day is :" + Days[next]);
        }
    }

    public void prevDay() {
        int prev = 0;

        if ((d > 0) && (d < 6)) {
            prev = (this.d) - 1;
            System.out.println("previous day is " + Days[prev]);
        } else
            System.out.println("previous day id " + Days[6]);
    }

    public int calcDay(int num) {
        int newDay;
        this.d = d + num;
        newDay = this.d % 7;
        System.out.println("calc day is" + Days[d]);
        return newDay;
    }

    public void print() {
        System.out.println("day is " + Days[d]);
    }

    public static void main(String[] args) {
        String day;
        Day Callmethod = new Day();
        Scanner console = new Scanner(System.in);
        System.out.println("enter a day of the week");
        day = console.nextLine();
        Callmethod.print();
        Callmethod.nexDay();
        Callmethod.prevDay();
        Callmethod.getDay();
    }
}

Answer 1

好吧，这个

 Day Callmethod = new Day();

正在调用你的空构造函数。不是带循环的构造函数（需要String）。此外，Java变量以小写字母开头（Callmethod看起来像class）。我认为你在寻找像

这样的东西

 Day day = new Day("SUNDAY");

此外，您的if需要大括号或return将被调用而不做任何事情（除非它与第一个条目匹配），如

for(int i=0;i<Days.length;i++){
    if (strDay.equalsIgnoreCase(Days[i])) {
      d = i;
      return;
    }
 }

Answer 2

尝试改变这个：

public Day(String strDay)/// this is my issue. I think I am going about this constructor all wrong
  {
      for(int i=0;i<Days.length;i++){

          if (strDay.equalsIgnoreCase(Days[i]))
              d = i;
          return;

      }
  }

为此：

public Day(String strDay)/// this is my issue. I think I am going about this constructor all wrong
  {
      for(int i=0;i<Days.length;i++){
          if (strDay.equalsIgnoreCase(Days[i]))
          {
              d = i;
              return;
          }

      }
  }

如果没有花括号，您的条件块将只是下一行代码。所以你的循环只运行一次

循环将无法正常执行

2 个答案: