java - 是什么原因导致这个 "Incompatible operand types int and java.lang.String"

Question

我在 if 行上得到不兼容的操作数类型 int 和 java.lang.String。我不知道它在问什么或如何解决它。

import java.io.*;
import static java.lang.System.*;

//不确定是否需要上面的导入 导入java.util.Scanner;

class Main{

     public static void main (String str[]) throws IOException {

          Scanner scan = new Scanner(System.in);

           String ap = "April";
           String mar = "March";

      int one = 1;
      int two = 2;

      System.out.println("What month were you born in? (number)");
      int month = scan.nextInt();
      System.out.println("What day (number)");
      int day = scan.nextInt();
      if(((month == ap) && (day <= 19) || (month == mar) && (day >= 21))){
           System.out.println("Your birthday is: "+ month+ " "+day);
           System.out.println("Aries");
           System.out.println("Horoscope: ");
      }else
           System.out.println("HI"); //Just some filler code for compiling 



     }

}

Answer 1

您无法直接比较String和int(您可以获取int的String值但我不认为这会对您有帮助)，在您的用例中对我来说唯一有意义的导入静态是 java.util.Calendar.*。然后你需要从输入的月份中减一，因为Java认为Calendar.JANUARY (第一个月和 Static Import 的作用)为月份 0。最后，当您的输入不在预期范围内时，请显示一些有意义的内容而不是“HI”。类似的东西

import java.io.IOException;
import java.util.Scanner;
import static java.util.Calendar.*;

class Main {
    public static void main(String str[]) throws IOException {
        Scanner scan = new Scanner(System.in);
        System.out.println("What month were you born in? (number)");
        int month = scan.nextInt() - 1;
        System.out.println("What day (number)");
        int day = scan.nextInt();
        if (((month == APRIL) && (day <= 19) || 
                (month == MARCH) && (day >= 21))) {
            System.out.println("Your birthday is: " + month + " " + day);
            System.out.println("Aries");
            System.out.println("Horoscope: ");
        } else {
            System.out.printf("Month %d, Day %d%n", month, day);
        }
    }
}