Java設計模式 create Prototype

原型模式定義:
用原型實例指定建立對象的種類,而且經過拷貝這些原型建立新的對象.

Prototype模式容許一個對象再建立另一個可定製的對象，根本無需知道任何如何建立的細節,工做原理是:經過將一個原型對象傳給那個要發動建立的對象，這個要發動建立的對象經過請求原型對象拷貝它們本身來實施建立。

如何使用?
由於Java中的提供clone()方法來實現對象的克隆,因此Prototype模式實現一會兒變得很簡單.

import java.util.Hashtable;

public class SymbolLoader  {
    private Hashtable symbols = new Hashtable();
    public SymbolLoader() {
           symbols.put("Line", new LineSymbol());
           symbols.put("Note", new NoteSymbol());
    }
    public Hashtable getSymbols() {
        return symbols;
    }
}

public class LineSymbol extends Graphic {
    public LineSymbol() {
    }

    public void DoSomething() {
        System.out.println("I am used to draw a line !");
    }
}

public class NoteSymbol extends Graphic {
    public NoteSymbol() {
    }

    public void DoSomething() {
        System.out.println("I am used to draw a note !");
    }
}

public interface IGraphic extends Cloneable, Serializable {
    public String getName() ;
    public void setName(String gName);
}

public abstract class Graphic implements IGraphic {
    private String name;
    
    public Object clone() {
        try {
            return super.clone();
        } catch (CloneNotSupportedException e){
            System.out.println("Do not support clone !!!");
            throw new InternalError();
        }
    }
   
    /* (non-Javadoc)
     * @see corner.dp.create.Prototype.mypackage.IGraphic#getName()
     */
    public String getName() {
        return name;
    }
    
    /* (non-Javadoc)
     * @see corner.dp.create.Prototype.mypackage.IGraphic#setName(java.lang.String)
     */
    public void setName(String gName) {
        name = gName;
    }

    public abstract void DoSomething();
}

測試代碼：

public class GraphicTool  {
    public static void main(String[] args) {
        //-----  Initial our prototype instance  ---------- 
        SymbolLoader myLoader = new SymbolLoader();
        Hashtable mySymbols = myLoader.getSymbols();

        //-----  Draw a Line  -------------------------------
        Graphic myLine = (Graphic)((Graphic)mySymbols.get("Line")).clone();
        myLine.DoSomething();
    }
}