Why am I not getting the right return message?
<p>Below I have a snippet of code that I won't work. I get input in my main method then pass that input into another method to check for validation. But it doesn't really check correctly. If I input <code>99</code> for <code>month</code> and <code>day</code> I expect it to give me the message <code>Check Month</code>. </p>

<p>Instead I get:
   <code>THIS
    THIS</code></p>

<p>If I input <code>02</code> for month and <code>99</code> for day, I expect it to give me the message: <code>Check day</code>.  Instead I get <code>THIS THIS</code></p>

<p>If I input <code>02</code> for both, I expect it to run and continue running other methods. Instead I get <code>THIS THIS</code>.</p>

<pre><code>public class Date {

private Calendar parsedDate;

public static void main(String[] args) 
{
    Date main = new Date();
        System.out.println("Enter a date (use the format -&gt; (MM/DD/YYYY)");

    //declare Scanner
    Scanner in = new Scanner (System.in);

    System.out.println("Enter a month (MM): ");
    String month = in.nextLine();

    System.out.println("Enter a day (DD): ");
    String day = in.nextLine();

    System.out.println("Enter a year (YYYY): ");
    String year = in.nextLine();

    if (main.isValidDate(month, day, year) == true) 
    {
        main.newFormat(month, day, year);
        main.isLeapYear(year);
        main.dayNumber(month, day);
    }
    else if (main.isValidDate(month, day, year) == false)
    {
        System.out.println("Invalid Input");
    }
}//end of main

private boolean isValidDate(String month, String day, String year) 
{
    //check month       
    if(month == "01" || month == "03" || month == "04" ||
       month == "05" || month == "06" || month == "07" || month == "08" ||
       month == "09" || month == "10" || month == "11" || month == "12")
    { 
        //check day
        if(day == "01" || day == "02" || day == "03" || day == "04" ||
           day == "05" || day == "06" || day == "07" || day == "08" ||
           day == "09" || day == "10" || day == "11" || day == "12" ||
           day == "13" || day == "14" || day == "15" || day == "16" ||
           day == "17" || day == "18" || day == "19" || day == "20" ||
           day == "21" || day == "22" || day == "23" || day == "24" ||
           day == "25" || day == "26" || day == "27" || day == "28" ||
           day == "29" || day == "30" || day == "31")
        {
            return true;
        }
        else
        {
            System.out.println("Check Day");
            return false;
        }
    }//end of check month
    else if (month == "02")
    {
        if (day == "28" || day == "29")
        {
            return true;
        }
    }//end of month 2
    else
    {
        System.out.println("THIS");
        return false;
    }

    parsedDate = null;// if it's valid set the parsed Calendar object up.
    return true;
}//end of isValidDate
</code></pre>
