Java的建造设计模式

分为指导者，抽象建造者，具体建造者
有一个例子

import java.util.*;
import junit.framework.*;

//不同的媒体形式:

class Media extends ArrayList {}
class Book extends Media {}
class Magazine extends Media {}
class WebSite extends Media {}

// 不同媒体的组成元素:

class MediaItem {
　private String s;
　public MediaItem(String s) { this.s = s; }
　public String toString() { return s; }
}

class Chapter extends MediaItem {
　public Chapter(String s) { super(s); }
}

class Article extends MediaItem {
　public Article(String s) { super(s); }
}

class WebItem extends MediaItem {
　public WebItem(String s) { super(s); }
}

// 抽象建造者角色，它规范了所有媒体建造的步骤:

class MediaBuilder {
　public void buildBase() {}
　public void addMediaItem(MediaItem item) {}
　public Media getFinishedMedia() { return null; }
}

//具体建造者角色

class BookBuilder extends MediaBuilder {
　private Book b;
　public void buildBase() {
　　System.out.println("Building book framework");
　　b = new Book();
　}

　public void addMediaItem(MediaItem chapter) {
　　System.out.println("Adding chapter " + chapter);
　　b.add(chapter);
　}
　public Media getFinishedMedia() { return b; }
}

class MagazineBuilder extends MediaBuilder {
　private Magazine m;
　public void buildBase() {
　　System.out.println("Building magazine framework");
　　m = new Magazine();
　}

　public void addMediaItem(MediaItem article) {
　　System.out.println("Adding article " + article);
　　m.add(article);
　}
　public Media getFinishedMedia() { return m; }
}

class WebSiteBuilder extends MediaBuilder {
　private WebSite w;
　public void buildBase() {
　　System.out.println("Building web site framework");
　　w = new WebSite();
　}

　public void addMediaItem(MediaItem webItem) {
　　System.out.println("Adding web item " + webItem);
　　w.add(webItem);
　}

　public Media getFinishedMedia() { return w; }
}

//指导者角色，也叫上下文
class MediaDirector {
　private MediaBuilder mb;
　public MediaDirector(MediaBuilder mb) {
　　this.mb = mb; //具有策略模式相似特征的
　}

　public Media produceMedia(List input) {
　　mb.buildBase();
　　for(Iterator it = input.iterator(); it.hasNext();)
　　　mb.addMediaItem((MediaItem)it.next());
　　　return mb.getFinishedMedia();
　}
};

//测试程序——客户程序角色

public class BuildMedia extends TestCase {
　private List input = Arrays.asList(new MediaItem[] {
　　new MediaItem("item1"), new MediaItem("item2"),
　　new MediaItem("item3"), new MediaItem("item4"),
　});

　public void testBook() {
　　MediaDirector buildBook = new MediaDirector(new BookBuilder());
　　Media book = buildBook.produceMedia(input);
　　String result = "book: " + book;
　　System.out.println(result);
　　assertEquals(result, "book: [item1, item2, item3, item4]");
　}

　public void testMagazine() {
　　MediaDirector buildMagazine = new MediaDirector(new

MagazineBuilder());
　　Media magazine = buildMagazine.produceMedia(input);
　　String result = "magazine: " + magazine;
　　System.out.println(result);
　　assertEquals(result, "magazine: [item1, item2, item3, item4]");
　}

　public void testWebSite(){
　　MediaDirector buildWebSite = new MediaDirector(new

WebSiteBuilder());
　　Media webSite = buildWebSite.produceMedia(input);
　　String result = "web site: " + webSite;
　　System.out.println(result);
　　assertEquals(result, "web site: [item1, item2, item3, item4]");
　}

　public static void main(String[] args) {
　　junit.textui.TestRunner.run(BuildMedia.class);
　}

}

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