User Date Input Validation without Date Library

I am on a project that requires me of the following:

1. 
   

   Validate date input by user without use of Date library. (Able to do)

   
   


2. 
   

   Prints the next date of the user input date if valid date is typed in. Example: User input 28 Feb 2010. Display 01 Mar 2010 as tomorrow's date. (To-Do)

   
   


3. 
   

   Asks user if he/she wishes to continue at the end of the program. (To-Do)

   
   

   ---

Current additional problems:

1. 
   

   Unable to retrieve dateValid boolean value from above if/else statements.

   
   


2. 
   

   Unable to prompt user if he/she wishes to continue at the end of the output.

   
   

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Below is a sample of my code.

I would like to request for assistance.

Any help will be greatly appreciated

---

public static void main(String[] args)
{
    Scanner scan = new Scanner(System.in);

    boolean dateValid;

    System.out.println ("Enter the day: ");
    int day = scan.nextInt();

    System.out.println ("Enter the month: ");
    int month = scan.nextInt();

    System.out.println ("Enter the year: ");
    int year = scan.nextInt();


    if (month <= 1 && month >= 12)    //checks validity for user month input
    {
    dateValid=false;
    }

    else if((month==1) && (day>=1 && day<=31))    //the following are checks for each month, base on the number of days, including leap year check for Feb
    {
    dateValid=true;
    }


    //same if/else for the next few months



    if (dateValid=true)    //unable to get dateValid boolean value from above if/else statements
    {
        //TO-DO Print tomorrow's date
        //TO-DO Prompts user if he wishes to continue (Y/N?)
    }
    else
    {
        System.out.println("DATE INVALID");
        //TO-DO Prompts user if he wishes to continue (Y/N?)
    }

}