Hands-On Design Patterns with Java

Being purposeful with inheritance

Inheritance is a powerful OOP construct. We can model objects efficiently, as was illustrated with the bicycle. We know that the following relationships exist:

• Bicycle is a two wheeled
• Bicycle is a vehicle
• Bicycle is a object

When we program inheritance, we should perform the "IS A" Checks using the following pseudo-code logic:

if ( <new child object> is a <parent object> ) then relationship = True; else relationship = False

If our "IS A" Checks fails, then inheritance should be avoided. This is an important test that, with dedicated use, can help ensure that inheritance lines between objects are valid.

Let's create the "IS A" Checks for our Bicycle class. We will do this by using Java's instanceof operator. ...