Operations on objects

Even though we can't print times in an optimal format, we can still write methods that manipulate Time objects. In the next few sections, I will demonstrate several of the possible interfaces for methods that operate on objects. For some operations, you will have a choice of several possible interfaces, so you should consider the pros and cons of each of these:

pure function

Takes objects and/or primitives as arguments but does not modify the objects. The return value is either a primitive or a new object created inside the method.

modifier

Takes objects as arguments and modifies some or all of them. Often returns void.

fill-in method

One of the arguments is an "empty" object that gets filled in by the method. Technically, this is a type of modifier.