One of the ideas of object oriented programming is to have software objects imitate "real world" objects. Most real world objects are made up of smaller objects. For instance, a bicycle is an object, and it is an assembly of several objects: frame, wheels, gears, handle bars, and other parts. Some of those parts are, in turn, made up of yet smaller parts. A wheel is made of a rim, a tire, an inner tube, a hub, and many spokes.
As with real world objects, software objects are often composed of smaller software objects. This chapter shows how to do this in Java.
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Could we continue to break down a bicycle into smaller and smaller objects?