[Java知识库]设计模式：建造者模式

④建造者模式（Builder Pattern）

简介：

? 建造者模式使用多个简单的对象来构建一个复杂的对象。属于建造者模式。

实现方法：

1. 创建一个零件类组装接口。
2. 创建多个不同抽象类，与其实现类。
3. 调用零件类组装接口中方法对步骤2中多个实现类进行组装，创建出多种不同的实例。

优点：

1. 建造者独立，灵活性高，容易扩展。
2. 对于全局与细节的控制性较强。

缺点：

1. 生成的产品必须有共同点，生产范围受限。

2. 若内部出现复杂变化，建造类的扩展规模较大。

使用场景：

1. 系统需要的对象具有复杂的内部结构。
2. 需要的对象内部属性本身相互依赖。

特点：

• 基本部件不变，组合经常发生改变。
• 代码规模较大型。

图形实现：

代码实现：

Collocation.java:

public interface Collocation {
    String name();
    Color selectColor();
    float price();
}

Color.java:

public interface Color {
        String color();
}

Blue.java:

public class Blue implements Color{
        @Override
        public String color() {
            return "Blue";
        }
}

Black.java:

public class Black implements Color{
    @Override
    public String color() {
        return "black";
    }
}

Tee.java:

public abstract class Tee implements Collocation{
    @Override
    public Color selectColor() {
        return new Blue();
    }

    @Override
    public abstract float price();
}

Pants.java:

public abstract class Pants implements Collocation{
    @Override
    public Color selectColor() {
        return new Black();
    }

    @Override
    public abstract float price();
}

HLA.java:

public class HLA extends Tee{
    @Override
    public float price() {
        return 325.0f;
    }

    @Override
    public String name() {
        return "HLA";
    }
}

LV.java:

public class LV extends Tee{
    @Override
    public float price() {
        return 3250.0f;
    }

    @Override
    public String name() {
        return "LV";
    }
}

LEVIS.java:

public class LEVIS extends Pants{    
	@Override    
	public float price() {       
		return 525.0f;    
	}    
	@Override    
	public String name() {        
		return "LEVIS";    
	}
}

GXG.java:

public class GXG extends Pants{    
	@Override    
	public float price() {        
		return 125.0f;    
	}    
	@Override    
	public String name() {        
		return "GXG";    
	}
}

Clothes.java:

public class Clothes {    
private List<Collocation> collocations= new ArrayList<Collocation>();    
	public void addCollocation(Collocation collocation) {        
		collocations.add(collocation);    
	}   
	public float getCost() {        
		float cost = 0.0f;        
		for (Collocation collocation: collocations) {            
			cost += collocation.price();        
		}        
		return cost;    
	}    
	public void showCollocations() {        
		for (Collocation collocation: collocations) {            
		System.out.print("collocation: " + collocation.name());            
		System.out.print(", SelectColor : " + collocation.selectColor().color());            
		System.out.println(", Price : " + collocation.price());        
		}    
	}
}

ClothesBuilder.java:

public class ClothesBuilder {    
	public Clothes prepareNo1 (){        
		Clothes clothes = new Clothes();        
		clothes.addCollocation(new HLA());        
		clothes.addCollocation(new LEVIS());        
		return clothes;    
	}    
	public Clothes prepareNo2 (){        
		Clothes clothes = new Clothes();        
		clothes.addCollocation(new LV());        
		clothes.addCollocation(new GXG());        
		return clothes;    
	}
}

BuilderPatternDemo.java:

public class BuilderPatternDemo {    
	public static void main(String[] args) {        
		ClothesBuilder clothesBuilder = new ClothesBuilder();        
		Clothes No1 = clothesBuilder.prepareNo1();        
		System.out.println("No1");        
		No1.showCollocations();        
		System.out.println("Total Cost: " + No1.getCost());        
		System.out.println("--------------------");        
		Clothes No2 = clothesBuilder.prepareNo2();        
		System.out.println("No2");        
		No2.showCollocations();        
		System.out.println("Total Cost: " + No2.getCost());    
	}
}

主线程main()执行结果：

No1
Collocation : HLA, SelectColor : Blue, Price : 325.0
collocation: LEVIS, SelectColor : black, Price : 525.0
Total Cost: 850.0
--------------------
No2
Collocation : LV, SelectColor : Blue, Price : 3250.0
collocation: GXG, SelectColor : black, Price : 125.0
Total Cost: 3375.0