CSC 172 - Introduction to Algorithms and Data Structures

Dr. R. M. Siegfried

Assignment #5 - Writing An Immutable Class For Time

Due Friday, February 21, 2014

An immutable class is a class that has no mutators, so there is no way to change private properties. The way in which these are written and are used is a little bit different.

You are going to write a class called Time that has three private properties:

• hours - the number of hours since midnight
• minutes
• seconds

Both minutes and seconds have the usual meaning.

Your class will have 4 constructors:

• Time() - the default constructor which sets the time to midnight (all three properties are 0)
• Time(int newHours) - minutes and seconds are set to zero.
• Time(int newHours, int newMinutes) - seconds are set to zero.
• Time(int newHours, int newMinutes, int newSeconds) - all three properties are set to the values given.

Additionally write the following methods:

• public String toString() - which returns a String with the time in proper 12-hour format (with AM or PM)
• public void write() - which writes the time in 12-hour format (you can use toString() to do this.)
• public Time later(int extraHours) - returns a Time object extraHours hours later.
• public Time later(int extraHours, int extraMinutes) - returns a Time object extraHours hours and extraMinutes minutes later.
• public Time later(int extraHours, int extraMinutes, int extraSeconds) - returns a Time object extraHours hours, extraMinutes minutes and extraSeconds seconds later.

Write another class containing a main program that creates a Time object, and returns the time 4 hours, 27 minutes and 15 seconds later.

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