【建造者设计模式】Builder Pattern说：“使用逐步方法从简单对象构造复杂对象”
它通常用于无法在单个步骤中创建对象（如对复杂对象进行反序列化）的情况。
建造者设计模式的优势 构建器模式的主要优点如下：

• 它在对象的构造和表示之间提供了清晰的分隔。
• 它可以更好地控制施工过程。
• 它支持更改对象的内部表示。

用于构建器模式的UML示例
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生成器设计模式示例
要创建构建器设计模式的简单示例, 你需要执行以下6个步骤。

1. 创建打包界面
2. 创建2个抽象类CD和Company
3. 创建公司的2个实施类：Sony和Samsung
4. 创建CDType类
5. 创建CDBuilder类
6. 创建BuilderDemo类

1）创建打包界面

public interface Packing { public String pack(); public int price(); }

2）创建2个抽象类CD和Company 创建一个抽象类CD, 它将实现Packing接口。

public abstract class CD implements Packing{ public abstract String pack(); }

public abstract class Company extends CD{ public abstract int price(); }

3）创建公司的两个实现类：索尼和三星

public class Sony extends Company{ @Override public int price(){ return 20; } @Override public String pack(){ return "Sony CD"; } }//End of the Sony class.

public class Samsung extends Company { @Override public int price(){ return 15; } @Override public String pack(){ return "Samsung CD"; } }//End of the Samsung class.

4）创建CDType类

import java.util.ArrayList; import java.util.List; public class CDType { private List< Packing> items=new ArrayList< Packing> (); public void addItem(Packing packs) { items.add(packs); } public void getCost(){ for (Packing packs : items) { packs.price(); } } public void showItems(){ for (Packing packing : items){ System.out.print("CD name : "+packing.pack()); System.out.println(", Price : "+packing.price()); } } }//End of the CDType class.

5）创建CDBuilder类

public class CDBuilder { public CDType buildSonyCD(){ CDType cds=new CDType(); cds.addItem(new Sony()); return cds; } public CDType buildSamsungCD(){ CDType cds=new CDType(); cds.addItem(new Samsung()); return cds; } }// End of the CDBuilder class.

6）创建BuilderDemo类

public class BuilderDemo{ public static void main(String args[]){ CDBuilder cdBuilder=new CDBuilder(); CDType cdType1=cdBuilder.buildSonyCD(); cdType1.showItems(); CDType cdType2=cdBuilder.buildSamsungCD(); cdType2.showItems(); } }

上面例子的输出

CD name : Sony CD, Price : 20 CD name : Samsung CD, Price : 15

构建器模式的另一个真实示例
用于构建器模式的UML： 我们正在考虑一个必胜客的商业案例, 从中可以得到不同种类的匹萨和冷饮。
披萨可以是多种类型的Veg比萨或非Veg披萨??（例如奶酪比萨, 洋葱比萨, masala-pizza等）, 并具有4种尺寸, 即小, 中, 大, 特大。
冷饮可以有几种类型（例如百事可乐, 可乐, 露水, 雪碧, 芬达, 马萨酒, 林卡, Thums-up等）, 将分为3种尺寸, 小, 中, 大。

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建造者模式的真实例子 让我们逐步了解Builder设计模式的真实示例。
步骤1：创建一个界面项目, 代表比萨饼和冷饮。

publicinterfaceItem { public String name(); public String size(); public float price(); }// End of the interface Item.

步骤2：创建一个抽象类Pizza, 该类将实现到接口Item。

public abstract class Pizza implements Item{ @Override public abstract float price(); }

步骤3：创建一个抽象类ColdDrink, 该类将实现到接口Item。

public abstract class ColdDrink implements Item{ @Override public abstract float price(); }

步骤4：创建一个抽象类VegPizza, 它将扩展到抽象类Pizza。

public abstract class VegPizza extends Pizza{ @Override public abstract float price(); @Override public abstractString name(); @Override public abstractString size(); }// End of the abstract class VegPizza.

步骤5：创建一个抽象类NonVegPizza, 它将扩展到抽象类Pizza。

public abstract class NonVegPizza extends Pizza{ @Override public abstract float price(); @Override public abstract String name(); @Override public abstract String size(); }// End of the abstract class NonVegPizza.

步骤6：现在, 创建具体的子类SmallCheezePizza, MediumCheezePizza, LargeCheezePizza, ExtraLargeCheezePizza, 这些子类将扩展到抽象类VegPizza。

public class SmallCheezePizza extends VegPizza{ @Override public float price() { return 170.0f; } @Override public String name() { return "Cheeze Pizza"; } @Override public String size() { return "Small size"; } }// End of the SmallCheezePizza class.

public class MediumCheezePizza extends VegPizza{ @Override public float price() { return220.f; } @Override public String name() { return "Cheeze Pizza"; } @Override public String size() { return "Medium Size"; } }// End of the MediumCheezePizza class. < /textaera> < /div> < div id="filename"> File: LargeCheezePizza.java< /div> < div class="codeblock"> < textareaname="code" class="java"> public class LargeCheezePizza extends VegPizza{ @Override public float price() { return 260.0f; } @Override public String name() { return "Cheeze Pizza"; } @Override public String size() { return "Large Size"; } }// End of the LargeCheezePizza class.

public class ExtraLargeCheezePizza extends VegPizza{ @Override public float price() { return 300.f; } @Override public String name() { return"Cheeze Pizza"; } @Override public String size() { return "Extra-Large Size"; } }// End of the ExtraLargeCheezePizza class.

步骤7：现在, 类似地创建具体的子类SmallOnionPizza, MediumOnionPizza, LargeOnionPizza, ExtraLargeOnionPizza, 这些子类将扩展到抽象类VegPizza。

public class SmallOnionPizza extends VegPizza { @Override public float price() { return 120.0f; } @Override public String name() { return"Onion Pizza"; } @Override public String size() { return"Small Size"; } }// End of the SmallOnionPizza class.

public class MediumOnionPizza extends VegPizza { @Override public float price() { return 150.0f; } @Override public String name() { return"Onion Pizza"; } @Override public String size() { return"Medium Size"; } }// End of the MediumOnionPizza class.

public class LargeOnionPizza extendsVegPizza{ @Override public float price() { return 180.0f; } @Override public String name() { return "Onion Pizza"; } @Override public String size() { return"Large size"; } }// End of the LargeOnionPizza class.

public class ExtraLargeOnionPizza extends VegPizza { @Override public float price() { return 200.0f; } @Override public String name() { return"Onion Pizza"; } @Override public String size() { return"Extra-Large Size"; } }// End of the ExtraLargeOnionPizza class

步骤8：现在, 类似地创建具体的子类SmallMasalaPizza, MediumMasalaPizza, LargeMasalaPizza, ExtraLargeMasalaPizza, 这些子类将扩展到抽象类VegPizza。

public class SmallMasalaPizza extends VegPizza{ @Override public float price() { return 100.0f; } @Override public String name() { return"Masala Pizza"; } @Override public String size() { return"Samll Size"; } }// End of the SmallMasalaPizza class

public class MediumMasalaPizza extends VegPizza {@Override public float price() { return 120.0f; }@Override public String name() {return"Masala Pizza"; }@Override public String size() { return"Medium Size"; }

public class LargeMasalaPizza extendsVegPizza{ @Override public float price() { return 150.0f; }@Override public String name() {return"Masala Pizza"; }@Override public String size() { return"Large Size"; } } //End of the LargeMasalaPizza class

public class ExtraLargeMasalaPizza extends VegPizza { @Override public float price() { return 180.0f; }@Override public String name() {return"Masala Pizza"; }@Override public String size() { return"Extra-Large Size"; } }// End of the ExtraLargeMasalaPizza class

步骤9：现在, 创建具体的子类SmallNonVegPizza, MediumNonVegPizza, LargeNonVegPizza, ExtraLargeNonVegPizza, 这些子类将扩展到抽象类NonVegPizza。

public class SmallNonVegPizza extends NonVegPizza {@Override public float price() { return 180.0f; }@Override public String name() { return "Non-Veg Pizza"; }@Override public String size() { return "Samll Size"; }}// End of the SmallNonVegPizza class

public class MediumNonVegPizza extends NonVegPizza{@Override public float price() { return 200.0f; }@Override public String name() { return "Non-Veg Pizza"; }@Override public String size() { return "Medium Size"; }

public class LargeNonVegPizza extends NonVegPizza{@Override public float price() { return 220.0f; }@Override public String name() { return "Non-Veg Pizza"; }@Override public String size() { return "Large Size"; }}// End of the LargeNonVegPizza class

public class ExtraLargeNonVegPizza extends NonVegPizza { @Override public float price() { return 250.0f; }@Override public String name() { return "Non-Veg Pizza"; }@Override public String size() { return "Extra-Large Size"; }} // End of the ExtraLargeNonVegPizza class

步骤10：现在, 创建两个抽象类Pepsi和Coke, 它们将扩展抽象类ColdDrink。

public abstract class Pepsi extends ColdDrink {@Override public abstractString name(); @Override public abstractString size(); @Override public abstractfloat price(); }// End of the Pepsi class

public abstract class Cokeextends ColdDrink {@Override public abstractString name(); @Override public abstractString size(); @Override public abstractfloat price(); }// End of the Coke class< /textaea> < /div> < p> Step 11:< b> Now, create concrete sub-classes SmallPepsi, MediumPepsi, LargePepsi that will extend to the abstract class Pepsi.< /b> < /p> < div id="filename"> File: SmallPepsi.java< /div> < div class="codeblock"> < textareaname="code" class="java"> public class SmallPepsiextends Pepsi{@Override public String name() { return "300 ml Pepsi"; }@Override public float price() { return 25.0f; }@Override public String size() { return "Small Size"; } }// End of the SmallPepsi class

public class MediumPepsi extends Pepsi {@Override public String name() { return "500 ml Pepsi"; }@Override public String size() { return "Medium Size"; }@Override public float price() { return 35.0f; } }// End of the MediumPepsi class

public class LargePepsi extends Pepsi{ @Override public String name() { return "750 ml Pepsi"; }@Override public String size() { return "Large Size"; }@Override public float price() { return 50.0f; } }// End of the LargePepsi class

步骤12：现在, 创建具体的子类SmallCoke, MediumCoke, LargeCoke, 这些子类将扩展到抽象类Coke。

public class SmallCoke extends Coke{@Override public String name() { return "300 ml Coke"; }@Override public String size() {return "Small Size"; }@Override public float price() {return25.0f; } }// End of the SmallCoke class

public class MediumCoke extends Coke{@Override public String name() { return "500 ml Coke"; }@Override public String size() {return "Medium Size"; }@Override public float price() {return35.0f; } }// End of the MediumCoke class

public class LargeCoke extends Coke { @Override public String name() { return "750 ml Coke"; }@Override public String size() {return "Large Size"; }@Override public float price() {return50.0f; } }// End of the LargeCoke class< /textrea> < /div> < p> Step 13:< b> Create an OrderedItems class that are having Item objects defined above.< /b> < /p> < div id="filename"> File: OrderedItems.java< /div> < div class="codeblock"> < textareaname="code" class="java"> import java.util.ArrayList; import java.util.List; public class OrderedItems {List< Item> items=new ArrayList< Item> (); public void addItems(Item item){items.add(item); } public float getCost(){float cost=0.0f; for (Item item : items) { cost+=item.price(); } return cost; } public void showItems(){for (Item item : items) { System.out.println("Item is:" +item.name()); System.out.println("Size is:" +item.size()); System.out.println("Price is: " +item.price()); } }}// End of the OrderedItems class

步骤14：创建一个OrderBuilder类, 该类将负责创建OrderedItems类的对象。

import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; public class OrderBuilder { public OrderedItems preparePizza() throws IOException{OrderedItems itemsOrder=new OrderedItems(); BufferedReader br =new BufferedReader(new InputStreamReader(System.in)); System.out.println(" Enter the choice of Pizza "); System.out.println("============================"); System.out.println("1. Veg-Pizza"); System.out.println("2. Non-Veg Pizza"); System.out.println("3. Exit"); System.out.println("============================"); int pizzaandcolddrinkchoice=Integer.parseInt(br.readLine()); switch(pizzaandcolddrinkchoice) { case 1:{System.out.println("You ordered Veg Pizza"); System.out.println("\n\n"); System.out.println(" Enter the types of Veg-Pizza "); System.out.println("------------------------------"); System.out.println("1.Cheeze Pizza"); System.out.println("2.Onion Pizza"); System.out.println("3.Masala Pizza"); System.out.println("4.Exit"); System.out.println("------------------------------"); int vegpizzachoice=Integer.parseInt(br.readLine()); switch(vegpizzachoice) { case 1: { System.out.println("You ordered Cheeze Pizza"); System.out.println("Enter the cheeze pizza size"); System.out.println("------------------------------------"); System.out.println("1. Small Cheeze Pizza "); System.out.println("2. Medium Cheeze Pizza "); System.out.println("3. Large Cheeze Pizza "); System.out.println("4. Extra-Large Cheeze Pizza "); System.out.println("------------------------------------"); int cheezepizzasize=Integer.parseInt(br.readLine()); switch(cheezepizzasize) { case 1: itemsOrder.addItems(new SmallCheezePizza()); break; case 2: itemsOrder.addItems(new MediumCheezePizza()); break; case 3: itemsOrder.addItems(new LargeCheezePizza()); break; case 4: itemsOrder.addItems(new ExtraLargeCheezePizza()); break; case 2: { System.out.println("You ordered Onion Pizza"); System.out.println("Enter the Onion pizza size"); System.out.println("----------------------------------"); System.out.println("1. Small Onion Pizza "); System.out.println("2. Medium Onion Pizza "); System.out.println("3. Large Onion Pizza "); System.out.println("4. Extra-Large Onion Pizza "); System.out.println("----------------------------------"); int onionpizzasize=Integer.parseInt(br.readLine()); switch(onionpizzasize) { case 1: itemsOrder.addItems(new SmallOnionPizza()); break; case 2: itemsOrder.addItems(new MediumOnionPizza()); break; case 3: itemsOrder.addItems(new LargeOnionPizza()); break; case 4: itemsOrder.addItems(new ExtraLargeOnionPizza()); break; } } break; case 3: { System.out.println("You ordered Masala Pizza"); System.out.println("Enter the Masala pizza size"); System.out.println("------------------------------------"); System.out.println("1. Small Masala Pizza "); System.out.println("2. Medium Masala Pizza "); System.out.println("3. Large Masala Pizza "); System.out.println("4. Extra-Large Masala Pizza "); System.out.println("------------------------------------"); int masalapizzasize=Integer.parseInt(br.readLine()); switch(masalapizzasize) { case 1: itemsOrder.addItems(new SmallMasalaPizza()); break; case 2: itemsOrder.addItems(new MediumMasalaPizza()); break; case 3: itemsOrder.addItems(new LargeMasalaPizza()); break; case 4: itemsOrder.addItems(new ExtraLargeMasalaPizza()); break; }} break; }} break; // Veg- pizza choice completed.case 2: { System.out.println("You ordered Non-Veg Pizza"); System.out.println("\n\n"); System.out.println("Enter the Non-Veg pizza size"); System.out.println("------------------------------------"); System.out.println("1. Small Non-VegPizza "); System.out.println("2. Medium Non-VegPizza "); System.out.println("3. Large Non-VegPizza "); System.out.println("4. Extra-Large Non-VegPizza "); System.out.println("------------------------------------"); int nonvegpizzasize=Integer.parseInt(br.readLine()); switch(nonvegpizzasize) {case 1: itemsOrder.addItems(new SmallNonVegPizza()); break; case 2: itemsOrder.addItems(new MediumNonVegPizza()); break; case 3: itemsOrder.addItems(new LargeNonVegPizza()); break; case 4: itemsOrder.addItems(new ExtraLargeNonVegPizza()); break; }} break; default: { break; } }//end of main Switch//continued?.. System.out.println(" Enter the choice of ColdDrink "); System.out.println("============================"); System.out.println("1. Pepsi"); System.out.println("2. Coke"); System.out.println("3. Exit"); System.out.println("============================"); int coldDrink=Integer.parseInt(br.readLine()); switch (coldDrink) { case 1: { System.out.println("You ordered Pepsi "); System.out.println("Enter thePepsi Size "); System.out.println("------------------------"); System.out.println("1. Small Pepsi "); System.out.println("2. Medium Pepsi "); System.out.println("3. Large Pepsi "); System.out.println("------------------------"); int pepsisize=Integer.parseInt(br.readLine()); switch(pepsisize) { case 1: itemsOrder.addItems(new SmallPepsi()); break; case 2: itemsOrder.addItems(new MediumPepsi()); break; case 3: itemsOrder.addItems(new LargePepsi()); break; } } break; case 2: { System.out.println("You ordered Coke"); System.out.println("Enter the Coke Size"); System.out.println("------------------------"); System.out.println("1. Small Coke "); System.out.println("2. Medium Coke"); System.out.println("3. Large Coke"); System.out.println("4. Extra-Large Coke "); System.out.println("------------------------"); int cokesize=Integer.parseInt(br.readLine()); switch(cokesize) { case 1: itemsOrder.addItems(new SmallCoke()); break; case 2: itemsOrder.addItems(new MediumCoke()); break; case 3: itemsOrder.addItems(new LargeCoke()); break; }} break; default: { break; }}//End of the Cold-Drink switch return itemsOrder; } //End of the preparePizza() method

第15步：创建一个将使用OrderBuilder类的BuilderDemo类。

import java.io.IOException; public class BuilderDemo {public static void main(String[] args) throws IOException { // TODO code application logic hereOrderBuilder builder=new OrderBuilder(); OrderedItems orderedItems=builder.preparePizza(); orderedItems.showItems(); System.out.println("\n"); System.out.println("Total Cost : "+ orderedItems.getCost()); } }// End of the BuilderDemo class

输出量
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