What is the difference between Abstraction and Polymorphism

Question

I seem to not understand two OOP concepts very well. Could you explain what abstraction and polymorphism are, preferably with real examples and

Answer 1

Both terms are used heavily in object oriented programming, but they are not specifically limited to that context.

Abstraction is a generalization of something else; a step higher in perspective. A heirarchy for instance can be seen as an abstraction on the organizational structure of a company. Generally it is used in the context of what things are underneath (such as their base types). The point of abstracting is to write less code that is more general in nature, so that you can run it for a larger set of problems. A spreadsheet for example is an abstraction that allows for a specific type of information storage. More?

Polymorphism is also a generalization, but one that occurs in a runtime context. A bunch of different object types are polymorphic if there is some way to access them where they are indistinguishable from each other. That is, all of the objects look and feel the same, even if they are not. The purpose of this is to significantly reduce code; you can write one generalized solution to save from writing all of the different permutations for each different type. If you write a graphics library, you'd rather just write some abstract code to handle 'shapes', then have to write code for each different type, such as circles, squares, etc.

These are both terms that are centered around properties in the code that will enable the programmers to do more with less. Less code has less bugs, is more stable and is easier to maintain. The alternative is to use "brute force" to pound out millions and million of lines of very specific (and very fragile) code. More code is harder to fix, and much harder to keep up-to-date.

Paul.