Alternative if statement & toString

[Steve Cooke]

I had to write a program for class to check and validate a date is correct. Check if year is between a certain range, check to make sure month is between 1 & 12. Then verify that there is the correct number of days in each month, along with check to see if it's a leap year or not for feb.

The if statements I wrote work but is there a way to clean this up a bit more or an alternative?

Then last part would be the toString. I still havent heard that if the date displays if it needs to be MM/DD/YYYY, or if it can be M/D/YYYY ex 02/02/2000 or 2/2/2000.

I know that using StringBuffer i can append, but how would I add the 0 before the day or month. I'm still tinkering with it, but not seeing any other solutions. I'm just going to assume that the date format needs to be 02/02/2000

Thanks in advance.

MyDate class

public class MyDate
{
    // Instance variables - each MyDate object created with 'new' has its own set.
    private int mYear;
    private int mMonth;
    private int mDay;
 
    /**
     * Set the date value for this MyDate object. If any of the parameter values are
     * illegal values, the date is set to 00/00/0000.
     *
     * @param   year    the year.
     * @param   month   the month.
     * @param   day     the day.
     */
    public void setDate (int year, int month, int day)
    {
        // Check validity of parameters for setting this date.  If any of
        // them are invalid, set the instance variables to zero representing
        // an invalid date. If they represent a valid date, set the instance
        // variables to the specified date.
 
        //check to make sure year is within range
    if (year < 1800 || year > 2020)
        {
            // Clear state of object if invalid parameter values
            mYear = 0;
            mMonth = 0;
            mDay = 0;
            return;
        }
        
        //check to make sure month in between 1 & 12
    if (month < 0 || month > 12)
        {
           mYear = 0;
           mMonth = 0;
           mDay = 0;
           return;
        }
        
        //check to see what month has been input to verify if 30 or 31 days
    if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12)
        {
        if (day < 1 || day > 31)
            {
            mYear = 0;
            mMonth = 0;
            mDay = 0;
            return;
            }
        }
        
        //check to see what month has been input to verify if 30 or 31 days
    if (month == 4 || month == 6 || month == 9 || month == 11)
        {
        if (day < 1 || day > 30)
        {
        mYear = 0;
        mMonth = 0;
        mDay = 0;
        return;
        }
        }
        
        //if month is 2, check to see if leap year, if so make sure date is between 1 & 29
    int iLeap = year % 4;
        if (month == 2 && iLeap == 0)
        {
        if (day < 1 || day > 29)
        {
        mYear = 0;
        mMonth = 0;
        mDay = 0;
        return;
        }
        }
        
        //if month is 2 and not a leap year, make sure date is between 1 & 28
        if (month == 2 && iLeap != 0)
        {
        if (day < 1 || day > 28)
        {
        mYear = 0;
        mMonth = 0;
        mDay = 0;
        return;
        }
        }
        
        // Date is valid - set 'this' object's state (instance variables).
        mYear = year;
        mMonth = month;
        mDay = day;
        
    }
 
    /**
     * Returns true if this MyDate object represents a valid date.
     *
     * @return true if this object represents a valid date, false otherwise.
     */
    public boolean isValidDate()
    {
        if (mYear == 0 || mMonth == 0 || mDay == 0)
        {
        return false;  // TODO - replace
        }
        else
        {
        return true;
        }
    }
 
    /**
     * Returns the year value represented by this MyDate.
     *
     * @return the year represented by this object as an int.
     */
    public int getYear()
    {
        return mYear; // TODO - replace
    }
 
    /**
     * Returns the month value represented by this MyDate.
     *
     * @return the month represented by this object as an int.
     */
    public int getMonth()
    {
        return mMonth; // TODO - replace
    }
 
    /**
     * Returns the day value represented by this MyDate.
     *
     * @return the day represented by this object as an int.
     */
    public int getDay()
    {
        return mDay; // TODO - replace
    }
 
    /**
     * Returns true if this MyDate represents a leap year.
     *
     * @return  true if this object represents a date that is a leap year, false otherwise.
     */
    public boolean isLeapYear()
    {
        int iLeap = mYear % 4;
        
    if (iLeap == 0)
        {
        return true;
        }
        else
        {
        return false;  // TODO - replace
        }
    
    }
 
    /**
     * Returns the date value represented by this MyDate as a String - MM/DD/YYYY.
     *
     * @return the date value represented by this object as a String of the form MM/DD/YYYY.
     */
    public String toString()
    {
        if (mMonth < 10)
        {
        mMonth = '0' + mMonth;
        }
        if (mDay < 10)
        {
        mDay = '0' + mDay;
        }
                
    return mMonth + "/" + mDay + "/" + mYear;  // TODO - replace
        
    }
 
}

MyDateDemo Class

/*
 * MyDateDemo - tests the MyDate class.
 *
 * The MyDate class must be compiled before this class can be compiled.
 */
import java.util.Scanner;
public class MyDateDemo
{
    /**
     * main
     */
    public static void main (String[] args)
    {
        Scanner sc = new Scanner(System.in);
 
        // Ask for dates to be input, set the date, then test if date is valid
        int inYear, inMonth, inDay;
        do {
            System.out.println();
            System.out.println("Enter a year month and day (-1 to exit)");
            inYear = sc.nextInt();
            if (-1 == inYear)
                break;
            inMonth = sc.nextInt();
            inDay = sc.nextInt();
            System.out.println();
            System.out.println("Values read were: " + inYear + " " +
                inMonth + " " + inDay);
 
            // Create a new MyDate object and assign its reference to 'd'.
            MyDate d = new MyDate();
 
            // Set the object's date to the values read, then test if date is valid
            d.setDate(inYear, inMonth, inDay);
 
            if (d.isValidDate()) {
                System.out.println(d.toString());
                System.out.println("Year is " + d.getYear() +
                    "  month is " + d.getMonth() + "  day is " + d.getDay());
 
                if (d.isLeapYear())
                    System.out.println(d.getYear() + " IS a leap year");
                else
                    System.out.println(d.getYear() + " is NOT a leap year");
            } else {
                System.out.println("Date is invalid");
            }
 
        } while (-1 != inYear);
 
        // Keep console window alive until 'enter' pressed (if needed).
        System.out.println();
        System.out.println("Done - press enter key to end program");
        String junk = sc.nextLine();
    }
}

[Stan James]

Look into DateFormat and SimpleDateFormat. You can use a DateFormat to parse a string into a Date object. It will throw an exception if the string is not valid. See the setLenient method, too.

[Justin Fox]

if i were you, i would use a switch statement for every month, it would be
a whole lot easier..

and by the way, ive done that assignment in lab Before lol..

Monk