使用Java中的日期验证程序获取不正确的结果

Question

I have to keep the program basic, nothing too fancy. Here is my problem: When I enter the date "11/31/2013" it returns "Incorrect day input for a regular month with 30 days". I understand this means there is a problem with structure of my If/Else statement and/or my boolean expressions. Yet I can't seem to figure out the problem. Any help is appreciated, thank you.

Here is my program:

import java.util.Scanner;

public class DateValidation {

public static void main(String[] args) {

    Scanner keyboard = new Scanner(System.in);
    String date;
    System.out.println("Please enter a date in the following format: mm/dd/yyyy ");
    date = keyboard.next();

    int month = Integer.parseInt(date.substring(0, 2));
    int day = Integer.parseInt(date.substring(3, 5));
    int year = Integer.parseInt(date.substring(6, 10));
    boolean isLeapYear = ((year % 4 == 0) && (year % 100 != 0) || (year % 400 == 0));
    boolean thirtyMonth = (month == 9 || month == 4 || month == 5 || month == 10);
    boolean regMonth = (month == 1 || month == 3 || month == 6 || month == 7 || month == 8 || month == 11 || month == 12);

    if ((month <= 0) || (day <= 0) || (day >= 32)) {
        System.out.println("You entered an incorrect month or day value");
    }
    if ((month == 2) && (isLeapYear == true) && (day > 0) && (day <= 29)) {
        System.out.println("it's a leap year - the date is " + date);
        System.exit(0);
    } else if ((month == 2) && (isLeapYear == false) && (day > 0) && (day <= 28)) {
        System.out.println("it's not a leap year - the date is " + date);
        System.exit(0);
    } else if (month == 2) {
        System.out.println("Your input is invald. Non leap-years only have 28 days");
        System.exit(0);
    }

    if ((thirtyMonth == true) && (day > 0) && (day <= 30)) {
        System.out.println("This is a valid date for a 30 day month  - here is the date " + date);
        System.exit(0);
    } else if ((thirtyMonth == true) && (day < 0) || (day >= 31)) {
        System.out.println("Incorrect day input for a regular month with 30 days");
        System.exit(0);
    }

    if ((regMonth) && (day > 0) && (day <= 31)) {
        System.out.println("This is a valid date for a regular month with 31 days - here is the date " + date);
        System.exit(0);
    } else if ((regMonth) && (day < 0) && (day >= 32)) {
        System.out.println("Incorrect day input for a regular month with 31 days");
        System.exit(0);
    }


}

}

Answer 1

April,June Sep and November are 30 days month

boolean thirtyMonth = (month == 9 || month == 4 || month == 5 || month == 10);

should be

boolean thirtyMonth = (month == 9 || month == 4 || month == 6 || month == 11);
boolean regMonth = (month == 1 || month == 3 || month == 5 ||month == 7 || month == 8 || month == 10 || month == 12);

Answer 2

change

    } else if ((thirtyMonth == true) && (day < 0) || (day >= 31)) {

to

    } else if (thirtyMonth && (day < 0 || day >= 31)) {