建造者模式可以将一个产品的内部表象与产品的生成过程分割开来，从而可以使一个建造过程生成具有不同的内部表象的产品对象。

UML图示：


1. com.cleversoft.designpatterns.builder2.PostalClert.java:
package com.cleversoft.designpatterns.builder2;

public class PostalClert {
    public void construct(LetterBuilder letterBuilder) {
        letterBuilder.buildEnvelop();
        letterBuilder.buildStamp();
    }
}

2. com.cleversoft.designpatterns.builder2.LetterBuilder.java:
package com.cleversoft.designpatterns.builder2;

public abstract class LetterBuilder {
    public abstract void buildEnvelop();

    public abstract void buildStamp();

    public abstract Letter getLetter();
}

3. com.cleversoft.designpatterns.builder2.OrdinaryMailBuilder.java:
package com.cleversoft.designpatterns.builder2;

public class OrdinaryMailBuilder extends LetterBuilder {
    private Letter ordinaryMail = new OrdinaryMail();

    public void buildEnvelop() {
        ordinaryMail.add("ordinaryEnvelop", 0.1);
    }

    public void buildStamp() {
        ordinaryMail.add("ordinaryStamp", 1.0);
    }

    public Letter getLetter() {
        return ordinaryMail;
    }

}

4. com.cleversoft.designpatterns.builder2.RegisteredLetterBuilder.java:
package com.cleversoft.designpatterns.builder2;

public class RegisteredLetterBuilder extends LetterBuilder {
    private Letter registeredLetter = new RegisteredLetter();

    public void buildEnvelop() {
        registeredLetter.add("registeredEnvelop", 2.0);
    }

    public void buildStamp() {
        registeredLetter.add("registeredStamp", 15.0);
    }

    public Letter getLetter() {
        return registeredLetter;
    }
}

5. com.cleversoft.designpatterns.builder2.Letter.java:
package com.cleversoft.designpatterns.builder2;

public interface Letter {

    public abstract void add(String type, double price);

    public abstract void list();

}

6. com.cleversoft.designpatterns.builder2.OrdinaryMail.java:
package com.cleversoft.designpatterns.builder2;

import java.util.Enumeration;
import java.util.Hashtable;

public class OrdinaryMail implements Letter {
    Hashtable<String, Double> letter = new Hashtable<String, Double>();

    /*
     * (non-Javadoc)
     * 
     * @see com.cleversoft.designpatterns.builder2.ILetter#add(java.lang.String,
     *      double)
     */
    public void add(String type, double price) {
        letter.put(type, price);
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.cleversoft.designpatterns.builder2.ILetter#show()
     */
    public void list() {
        System.out.println("Ordinary Letter List\n");
        Enumeration keys = letter.keys();
        while (keys.hasMoreElements()) {
            String key = keys.nextElement().toString();
            String value = letter.get(key).toString();
            System.out.println(key + " " + value + "元");
        }

    }
}

7. com.cleversoft.designpatterns.builder2.RegisteredLetter.java:
package com.cleversoft.designpatterns.builder2;

import java.util.Enumeration;
import java.util.Hashtable;

public class RegisteredLetter implements Letter {
    Hashtable<String, Double> letter = new Hashtable<String, Double>();

    /*
     * (non-Javadoc)
     * 
     * @see com.cleversoft.designpatterns.builder2.ILetter#add(java.lang.String,
     *      double)
     */
    public void add(String type, double price) {
        letter.put(type, price);
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.cleversoft.designpatterns.builder2.ILetter#show()
     */
    public void list() {
        System.out.println("Registered Letter List\n");
        Enumeration keys = letter.keys();
        while (keys.hasMoreElements()) {
            String key = keys.nextElement().toString();
            String value = letter.get(key).toString();
            System.out.println(key + " " + value + "元");
        }

    }
}

8. com.cleversoft.designpatterns.builder2.Main.java:
package com.cleversoft.designpatterns.builder2;

public class Main {

    public static void main(String[] args) {
        LetterBuilder lb = new OrdinaryMailBuilder();
        PostalClert pc = new PostalClert();
        pc.construct(lb);

        Letter l = lb.getLetter();
        l.list();
    }
}


参考资料：
1. http://terrylee.cnblogs.com/archive/2005/12/19/299878.html
2. 《Java与模式》

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