Pattern Oop
Posted in cross stitch on 08/13/2010 02:39 pm by adminWhen do I use a Design Pattern from inheritance?
this is an OOP question
I can't think of a condition or situation when to use a design pattern or an inheritance
thanks, I'll keep that in mind.
I'll also check that book you've told me. =)
Before that you should understand the what is design pattern and inheritance and then difference.
Design Pattern:
What is the design pattern?
If a problem occurs over and over again, a solution to that problem has been used effectively. That solution is described as a pattern. The design patterns are language-independent strategies for solving common object-oriented design problems. When you make a design, you should know the names of some common solutions. Learning design patterns is good for people to communicate each other effectively. In fact, you may have been familiar with some design patterns, you may not use well-known names to describe them. SUN suggests GOF (Gang Of Four--four pioneer guys who wrote a book named "Design Patterns"- Elements of Reusable Object-Oriented Software), so we use that book as our guide to describe solutions. Please make you be familiar with these terms and learn how other people solve the code problems.
Do I have to use the design pattern?
If you want to be a professional Java developer, you should know at least some popular solutions to coding problems. Such solutions have been proved efficient and effective by the experienced developers. These solutions are described as so-called design patterns. Learning design patterns speeds up your experience accumulation in OOA/OOD. Once you grasped them, you would be benefit from them for all your life and jump up yourselves to be a master of designing and developing. Furthermore, you will be able to use these terms to communicate with your fellows or assessors more effectively.
Many programmers with many years experience don't know design patterns, but as an Object-Oriented programmer, you have to know them well, especially for new Java programmers. Actually, when you solved a coding problem, you have used a design pattern. You may not use a popular name to describe it or may not choose an effective way to better intellectually control over what you built. Learning how the experienced developers to solve the coding problems and trying to use them in your project are a best way to earn your experience and certification.
Remember that learning the design patterns will really change how you design your code; not only will you be smarter but will you sound a lot smarter, too.
How many design patterns?
Many. A site says at least 250 existing patterns are used in OO world, including Spaghetti which refers to poor coding habits. The 23 design patterns by GOF are well known, and more are to be discovered on the way.
Note that the design patterns are not idioms or algorithms or components.
What is the relationship among these patterns?
Generally, to build a system, you may need many patterns to fit together. Different designer may use different patterns to solve the same problem. Usually:
* Some patterns naturally fit together
* One pattern may lead to another
* Some patterns are similar and alternative
* Patterns are discoverable and documentable
* Patterns are not methods or framework
* Patterns give you hint to solve a problem effectively
Inheritance:
It is nothing but creating new items containing an original item's features without changing the original item.
nheritance is a large part of the reason that Object Oriented Programming is a powerful tool. It has the following advantages:
* you can customize and enhance working classes
* it is easier to reuse code
* you can take a more general class and modify to suit a particular situation
Terminology
There are a number of terms that you need to know to follow the examples:
field:
a variable that is part of a class
method:
a function that is part of a class
constructor:
a special method that is called when an object is created
superclass:
the class that is inherited from (the parent class)
subclass:
the class the does the inheriting (the child class)
extendsin Java the keyword extends means that a class will inherit from another class
overload:
a method is overloaded if there are two or more methods with the same name in a class. Each overloaded method has a different set of parameters. That's how you can tell which one will get called.
override:
a method is overridden if there is a method in the subclass that has the same name and the same set of parameters. The superclass method is then NOT inherited.
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