创建对象的设计模式

Question

have to create an abstract class, say Part. But there are two type of parts,

Part1: This part has 3 instance variables, inside,outside,middle

Part2: This part has 2 instance variables, top, bottom

Finally, both Part are extending an abstract class Part, so finally, in Java its like this

abstract Class Object{
   public abstract String toString();
}

abstract class Part{
    abstract void print();
}

Class Part1 extends Part1{
    List <Object> inside = new ArrayList <Object> ();
    List <Object> outside = new ArrayList <Object> ();
    List <Object> medium = new ArrayList <Object> ();
    void print(){
        //go through all the list and print the object
    }
}

Class Part1 extends Part2{
    List <Object> top = new ArrayList <object> ();
    List <Object> bottom = new ArrayList <object> ();
    void print(){
        //go through all the list and print the object
    }
}

my issue is which design pattern can I apply for the creation of Part, I'm still a newbie in pattern, for me its builder because I have to come up with the same type of Object having different representation. But the object is not complex !!

Answer 1

See http://en.wikibooks.org/wiki/C%2B%2B_Programming/Code/Design_Patterns#Creational_Patterns .

I prefere factory pattern usage or prototype:

Prototype example:

Class PartsFactory
{
    Part createPart(string partType)
    {
        if (partType.equals("Type1")) return new Part1();
        if (partType.equals("Type2")) return new Part2();
        return null;
    }
}

Factory example:

interface PartsFactory
{
    Part createPart();
}

Class Parts1Factory implements PartsFactory
{
    Part createPart()
    {
        return new Part1();
    }
}

Class Parts2Factory implements PartsFactory
{
    Part createPart()
    {
        return new Part2();
    }
}