appending a zero/ formatting with toString

Question

The instructions are....starting with an empty string test the hours and append a zero to the string followed by the hours when there is one digit in the hours or append the two digit hours otherwise. Use final variable MIN_2DIGITS for your tests and only use the += operator to append the string being created....the code has to go into the comment code goes here close to the bottom, specifically i need to format the time in a way that the entered hours, minutes, seconds in the ##:##:## format

i have tried this so far but it only outputs 00:00:00 when a user enters hours, minutes, and seconds

public class Clock
{
  private static final byte DEFAULT_HOUR =  0,
                            DEFAULT_MIN  =  0,
                            DEFAULT_SEC  =  0,
                            MAX_HOURS    = 24,
                            MAX_MINUTES  = 60,
                            MAX_SECONDS  = 60;

  // ------------------
  // Instance variables
  // ------------------

 private byte seconds,
              minutes,
              hours; 

  public Clock (byte hours  , byte minutes  ,   byte seconds  )
  {
     setTime(hours, minutes, seconds);
  }

    public Clock (    )
  {
    setTime(DEFAULT_HOUR, DEFAULT_MIN, DEFAULT_SEC);
  }


//----------
// Version 2
//----------

  public String toString()

  {

    final byte MIN_2DIGITS = 10;

    String str = "";






// CODE GOES HERE, what i have below didn't work


 public String toString()

  {

    final byte MIN_2DIGITS = 10;

    String str = "";



           // my input

           if (hours < MIN_2DIGITS)
           {
             str += "0" + hours + ":" ;
           }
           else 
             str += hours;
           if (minutes < MIN_2DIGITS)
           {
             str += "0" + minutes + ":" ;
           }
            else
             str += minutes;
           if (seconds < MIN_2DIGITS)
           {
             str += "0" + seconds;
           }
           else
           str += seconds;



         //end of my input 

         return str;

       }







     return str;

   }


}  // End of class definition

Answer 1

You were almost there.

The following method needs to be added.

public void setTime(byte hours, byte minutes, byte seconds) {
    this.hours = hours;
    this.minutes = minutes;
    this.seconds = seconds;
}

Changes to the following method.

public String toString()
{
    final byte MIN_2DIGITS = 10;
    String str = "";
    // my input
    if (hours < MIN_2DIGITS) {
        str += "0" + hours + ":";
    } else
        str += hours + ":";
    if (minutes < MIN_2DIGITS) {
        str += "0" + minutes + ":";
    } else
        str += minutes + ":";
    if (seconds < MIN_2DIGITS) {
        str += "0" + seconds;
    } else
        str += seconds;
    // end of my input
    return str;
}

The method to test the code.

public static void main(String[] args) {
    Clock clock = new Clock((byte) 9, (byte) 10, (byte) 35);
    System.out.println(clock);
}