建造者模式

创建者模式又叫建造者模式，是将一个复杂的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表示。创建者模式隐藏了复杂对象的创建过程，它把复杂对象的创建过程加以抽象，通过子类继承或者重载的方式，动态的创建具有复合属性的对象。

简单来说，就是一个对象可能很复杂，但它的创建流程固定，只是注入的值不同。这个时候我们可以把对象的创建和表示分离，用户不需要知道对象具体有哪些属性，就可以完成创建。

举个例子

产品类：

public class Bike { 

    private IFrame frame; 
    private ISeat seat; 
    private ITire tire; 
    
    public IFrame getFrame() { 
        return frame; 
    } 
    public void setFrame(IFrame frame) { 
        this.frame = frame; 
    } 
    public ISeat getSeat() { 
        return seat; 
    } 
    public void setSeat(ISeat seat) { 
        this.seat = seat; 
    } 
    public ITire getTire() { 
        return tire; 
    } 
    public void setTire(ITire tire) { 
        this.tire = tire; 
    } 
} 

抽象Builder类：

// 抽象 builder 类 
public abstract class Builder { 
    abstract void buildFrame(); 
    abstract void buildSeat(); 
    abstract void buildTire(); 
    abstract Bike createBike(); 
} 

具体Builder类

// 具体 builder 类 
public class MobikeBuilder extends Builder{ 
    private Bike mBike = new Bike(); 
    @Override 
    void buildFrame() { 
        mBike.setFrame(new AlloyFrame()); 
    } 
    @Override 
    void buildSeat() { 
        mBike.setSeat(new DermisSeat()); 
    } 
    @Override 
    void buildTire() { 
        mBike.setTire(new SolidTire()); 
    } 
    @Override 
    Bike createBike() { 
        return mBike; 
    } 
} 

public class OfoBuilder extends Builder{ 
    private Bike mBike = new Bike(); 
    @Override 
    void buildFrame() { 
        mBike.setFrame(new CarbonFrame()); 
    } 
    @Override 
    void buildSeat() { 
        mBike.setSeat(new RubberSeat()); 
    } 
    @Override 
    void buildTire() { 
        mBike.setTire(new InflateTire()); 
    } 
    @Override 
    Bike createBike() { 
        return mBike; 
    } 
} 

指挥者Director:

public class Director { 
    private Builder mBuilder = null; 
    public Director(Builder builder) { 
        mBuilder = builder; 
    } 
    public Bike construct() { 
        mBuilder.buildFrame(); 
        mBuilder.buildSeat(); 
        mBuilder.buildTire(); 
        return mBuilder.createBike(); 
    } 
}

客户端调用：

public class Click { 
    public static void main(String[] args) { 
        showBike(new OfoBuilder()); 
        showBike(new MobikeBuilder()); 
    } 
    private void showBike(Builder builder) {
        Director director = new Director(builder); 
        Bike bike = director.construct(); 
        bike.getFrame().frame(); 
        bike.getSeat().seat(); 
        bike.getTire().tire(); 
    } 
} 

可以看到客户端并不知道产品创建的具体细节，它只是将想要产品对应的创建者传给指挥者Director类（因为创建流程是固定的！）