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Patterns

 
Greenhorn
Posts: 5
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Hi,
If possible give me some simple examples involving
Prototype,Singleton,Factory Method,Builder patterns.
-Nats
 
mister krabs
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Singleton is pretty simple. If you want only one instance of a class to exist at any one time, you use the Singleton pattern. The trick is to make the constructor private and add a static instance() method. The instance() method would check to see if an instance already exists...
if it doesn't it creates one, stores the pointer to it in a static variable, and returns the pointer.
If it does exist, it returns the pointer.
<pre>
public class SingletonSample {
private static SingletonSample singletonSample = null;
private SingletonSample() {}
public static SingletonSample instance() {

if (singletonSample == null)
singletonSample = new SingletonSample();
return singletonSample;
}
}

</pre>
 
Ranch Hand
Posts: 532
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Builder is when you wish to create a complex or aggregate object and builder encapsulates the creation and assembly of the parts. For example let's just say a car consists of the wheels, the engine and the remainder (body, etc). So to create the car, I need to create the wheels, create the engine, create the remainder and assemble this into the car. The CarBuilder would handle all of these details avoiding a very messy, overbloated Factory.
 
Ranch Hand
Posts: 34
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take a look at the pattern depo it has examples
 
Ranch Hand
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I remember when I was reading about Prototype in GoF, I decided that in Java it's equal to defining interface - which clients will know about - and set of concrete implementations to fill it. Or an abstract class with a Factory method. Is there anything I missed?
 
Ranch Hand
Posts: 31
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An interface can not implement any method while an abstract class can still have concrete implementations of its member functions. So by default an interface is a special case of an abstract class.
 
With a little knowledge, a cast iron skillet is non-stick and lasts a lifetime.
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