對(duì)象的結(jié)構(gòu)模式，又稱“部分－整體”模式。

合成模式將對(duì)象組織到樹(shù)結(jié)構(gòu)中，可以用來(lái)描述整體與部分的關(guān)系。合成模式可以使客戶端將單純?cè)嘏c復(fù)合元素同等對(duì)待。

適用場(chǎng)合：
1. 需要描述對(duì)象的部分和整體的等級(jí)結(jié)構(gòu)。
2. 需要客戶端忽略掉個(gè)體構(gòu)件和組合構(gòu)件的區(qū)別。客戶端必須平等對(duì)待所有的構(gòu)件，包括個(gè)體構(gòu)件和組合構(gòu)件。

優(yōu)點(diǎn)：
1. 合成模式可以很容易地增加新種類的構(gòu)件。
2. 使用合成模式可以使客戶端變得很容易設(shè)計(jì)，因?yàn)榭蛻舳瞬恍枰罉?gòu)件是樹(shù)葉構(gòu)件還是樹(shù)枝構(gòu)件。
缺點(diǎn)：
1. 使用合成模式后，控制樹(shù)枝構(gòu)件的類型就不太容易。
2. 用繼承的方法來(lái)增加新的行為很困難。


透明式的合成模式：
1. com.cleversoft.designpatterns.transparentcomposite.Graphics.java:

package ?com.cleversoft.designpatterns.transparentcomposite;

 abstract ? public ? class ?Graphics? {
???? public ? abstract ? void ?draw();

???? public ? abstract ? void ?add(Graphics?g);

???? public ? abstract ? void ?remove(Graphics?g);

???? public ? abstract ?Graphics?getChild( int ?i);
}

2. com.cleversoft.designpatterns.transparentcomposite.Circle.java:
package?com.cleversoft.designpatterns.transparentcomposite;

public?class?Circle?extends?Graphics?{
????public?void?draw()?{
????????System.out.println("Drawing?Circle");
????}

????public?void?add(Graphics?g)?{
????????//?do?nothing
????}

????public?void?remove(Graphics?g)?{
????????//?do?nothing
????}

????public?Graphics?getChild(int?i)?{
????????return?null;
????}
}

3. com.cleversoft.designpatterns.transparentcomposite.Line.java:
package?com.cleversoft.designpatterns.transparentcomposite;

public?class?Line?extends?Graphics?{
????public?void?draw()?{
????????System.out.println("Draw?Line");
????}

????public?void?add(Graphics?g)?{
????????//?do?nothing
????}

????public?void?remove(Graphics?g)?{
????????//?do?nothing
????}

????public?Graphics?getChild(int?i)?{
????????return?null;
????}
}

4. com.cleversoft.designpatterns.transparentcomposite.Rectangle.java:
package?com.cleversoft.designpatterns.transparentcomposite;

public?class?Rectangle?extends?Graphics?{
????public?void?draw()?{
????????System.out.println("Drawing?Rectangle");
????}

????public?void?add(Graphics?g)?{
????????//?do?nothing
????}

????public?void?remove(Graphics?g)?{
????????//?do?nothing
????}

????public?Graphics?getChild(int?i)?{
????????return?null;
????}
}

5. com.cleversoft.designpatterns.transparentcomposite.Picture.java:
package?com.cleversoft.designpatterns.transparentcomposite;

import?java.util.Vector;

public?class?Picture?extends?Graphics?{
????private?Vector<Graphics>?list?=?new?Vector<Graphics>(10);

????public?void?draw()?{
????????for?(int?i?=?0;?i?<?list.size();?i++)?{
????????????Graphics?g?=?(Graphics)?list.get(i);
????????????g.draw();
????????}
????}

????public?void?add(Graphics?g)?{
????????list.add(g);
????}

????public?void?remove(Graphics?g)?{
????????list.remove(g);
????}

????public?Graphics?getChild(int?i)?{
????????return?(Graphics)?list.get(i);
????}
}

6. com.cleversoft.designpatterns.transparentcomposite.Client.java:
package?com.cleversoft.designpatterns.transparentcomposite;

public?class?Client?{

????/**
?????*?Transparent?Composite
?????*/
????public?static?void?main(String[]?args)?{
????????Picture?p?=?new?Picture();
????????p.add(new?Circle());
????????p.add(new?Line());

????????Rectangle?r?=?new?Rectangle();
????????p.add(r);

????????p.draw();
????}

}


安全式的合成模式：
1. com.cleversoft.designpatterns.safecomposite.Graphics.java:
package?com.cleversoft.designpatterns.safecomposite;

abstract?public?class?Graphics?{
????public?abstract?void?draw();
}

2. com.cleversoft.designpatterns.safecomposite.Circle.java:
package?com.cleversoft.designpatterns.safecomposite;

public?class?Circle?extends?Graphics?{
????public?void?draw()?{
????????System.out.println("Drawing?Circle");
????}
}

3. com.cleversoft.designpatterns.safecomposite.Line.java:
package?com.cleversoft.designpatterns.safecomposite;

public?class?Line?extends?Graphics?{
????public?void?draw()?{
????????System.out.println("Drawing?Line");
????}
}

4. com.cleversoft.designpatterns.safecomposite.Rectangle.java:
package?com.cleversoft.designpatterns.safecomposite;

public?class?Rectangle?extends?Graphics?{
????public?void?draw()?{
????????System.out.println("Drawing?Rectangle");
????}
}

5. com.cleversoft.designpatterns.safecomposite.Picture.java:
package?com.cleversoft.designpatterns.safecomposite;

import?java.util.Vector;

public?class?Picture?extends?Graphics?{
????private?Vector<Graphics>?list?=?new?Vector<Graphics>(10);

????public?void?draw()?{
????????for?(int?i?=?0;?i?<?list.size();?i++)?{
????????????Graphics?g?=?(Graphics)?list.get(i);

????????????g.draw();
????????}
????}

????public?void?add(Graphics?g)?{
????????list.add(g);
????}

????public?void?remove(Graphics?g)?{
????????list.remove(g);
????}

????public?Graphics?getChild(int?i)?{
????????return?(Graphics)?list.get(i);
????}
}

6. com.cleversoft.designpatterns.safecomposite.Client.java:
package?com.cleversoft.designpatterns.safecomposite;

public?class?Client?{

????/**
?????*?Safe?Composite
?????*/
????public?static?void?main(String[]?args)?{
????????Picture?p?=?new?Picture();
????????p.add(new?Circle());
????????p.add(new?Line());

????????Rectangle?r?=?new?Rectangle();
????????p.add(r);

????????p.draw();
????}

}


參考資料：
1. 《Java與模式》
2. http://terrylee.cnblogs.com/archive/2006/03/11/347919.html

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