java - 我的无效和有效日期代码不显示

Question

我想编写一个代码来检查日期是否有效但是我的问题是输出。我无法显示用户是否输入了有效/无效的日期或月份。

    String date;

   int dd,mm,yyyy;

   boolean leapyear,validdate;




   if(mm >=1 || mm <=12) // to check if user input month which is less than 1 or more than 12
   {
       System.out.println(mm+" is an invalid month");
   }
   if((mm == 4 || mm == 6 || mm == 9 || mm == 11) && (dd <= 30)) // months with 30 days
        {
            validdate = true;
            System.out.println(mm + "/" + dd + "/" + yyyy + " is a valid date.");
        }

        //For months with 31 days
       else if((mm == 1 || mm == 3 || mm== 5 || mm == 7 || mm == 8 || mm == 10 || mm == 12) && (dd <= 31))
        {
            validdate = true;
            System.out.println(mm + "/"+ dd + "/" + yyyy + " is a valid date.");

        }

    else
       {

      System.out.println("Invalid date!");

   }




  }
}

}

Answer 1

if(mm >=1 || mm <=12) 

应该是

if (mm < 1 || mm > 12)

否则，mm 的每个值都将计算为true，从而使日期“无效”。