设计模式---Builder模式

本文主要是介绍设计模式---Builder模式，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

前言：

网络上有人将它定义为：将一个复杂对象的构建与它的表示分离，使得同样的构建过程可以创建不同的对象。
所以建造者模式适合于一个具有较多的零件（属性）的产品（对象）的创建过程。

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构成

由五个部分构成：
1. Product：ConcreateBuilder创建该产品的内部表示并定义它的装配过程。
2. Builder接口：抽象接口，定义创建Product对象内部各个组件的操作
3. ConcreteBuilder：实现Builder的接口，以构造和装配该产品的各个部件。定义并明确它所创建的表示，同时提供一个返回Product的接口
4. Director：构造一个使用Builder接口的对象

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实现

举个具体的例子吧：
现在我们需要生产一台电脑，有CPU，硬盘，内存，显卡，声卡（只是用来举例），我们可以这样写：

一：经典Builder模式

1.Product:

public class Computer {private CPU mCPU;                //CPUprivate HardDisk mHardDisk;      //硬盘private Memory mMemory;          //内存private Graphics mGraphics;      //显卡private SoundCard mSoundCard;    //声卡public HardDisk getmHardDisk() {return mHardDisk;}public void setmHardDisk(HardDisk mHardDisk) {this.mHardDisk = mHardDisk;}public CPU getmCPU() {return mCPU;}public void setmCPU(CPU mCPU) {this.mCPU = mCPU;}public Memory getmMemory() {return mMemory;}public void setmMemory(Memory mMemory) {this.mMemory = mMemory;}public Graphics getmGraphics() {return mGraphics;}public void setmGraphics(Graphics mGraphics) {this.mGraphics = mGraphics;}public SoundCard getmSoundCard() {return mSoundCard;}public void setmSoundCard(SoundCard mSoundCard) {this.mSoundCard = mSoundCard;}
}

2.Builder接口:

public interface Builder {public void createCPU();public void createHardDisk();public void createMemory();public void createGraphics();public void createSoundCard();public Computer getComputer();}

3.ConcreteBuilder:

public class ComputerBuilder implements Builder {private Computer mComputer = new Computer();@Overridepublic void createCPU() {mComputer.setmCPU(new CPU());}@Overridepublic void createHardDisk() {mComputer.setmHardDisk(new HardDisk());}@Overridepublic void createMemory() {mComputer.setmMemory(new Memory());   }@Overridepublic void createGraphics() {mComputer.setmGraphics(new Graphics());}@Overridepublic void createSoundCard() {mComputer.setmSoundCard(new SoundCard());}@Overridepublic Computer getComputer() {return mComputer;}
}

4.Director:

public class Director {private Builder mBuilder;public Director (Builder builder){this.mBuilder = builder;}public void CreateComputer(){this.mBuilder.createCPU();this.mBuilder.createHardDisk();this.mBuilder.createMemory();this.mBuilder.createGraphics();this.mBuilder.createSoundCard();}public Computer getComputer() {return this.mBuilder.getComputer();}
}

这种方式有一个缺点就是可能引入多个重载构造函数以及setters过度使用导致不必要的复杂性

二，通过静态内部类等方式实现的零件无序化构造

public class Computer {private final CPU mCPU;private final HardDisk mHardDisk;private final Memory mMemory;private final Graphics mGraphics;private final SoundCard mSoundCard;public Computer(ComputerBuilder builder) {mCPU = builder.mCPU;mHardDisk = builder.mHardDisk;mMemory = builder.mMemory;mGraphics = builder.mGraphics;mSoundCard = builder.mSoundCard;}public HardDisk getmHardDisk() {return mHardDisk;}public CPU getmCPU() {return mCPU;}public Memory getmMemory() {return mMemory;}public Graphics getmGraphics() {return mGraphics;}public SoundCard getmSoundCard() {return mSoundCard;}public static class ComputerBuilder {private final CPU mCPU;private final HardDisk mHardDisk;private final Memory mMemory;private Graphics mGraphics;private SoundCard mSoundCard;public ComputerBuilder(CPU cpu, HardDisk harddisk, Memory memory) {this.mCPU = cpu;this.mHardDisk = harddisk;this.mMemory = memory;}public ComputerBuilder graphics(Graphics graphics) {this.mGraphics = graphics;return this;}public ComputerBuilder soundCard(SoundCard soundCard) {this.mSoundCard = soundCard;return this;}public Computer build() {return new Computer(this);}}}

使用方法：

    public Computer CreateComputer() {return new Computer.ComputerBuilder(CPU, HardDisk, Memory).graphics(Graphics).soundCard(SoundCard).build();}

用这种方式方式看起来会非常直观，另外对话框AlertDialog也是用的这种形式

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