建造者模式(builder)

定义:讲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表示. 优点:封装性,容易扩展,便于控制细节风险 注意:建造者模式关注的是顺序,而工厂方法模式更多关注创建.

1.1. 角色:

产品类:通常实现了模板方法模式. 抽象建造者:规范产品的组件,即规范产品制造的流程结构. 具体建造者:实现抽象类定义的方法,并且返回一组建好的对象. 导演类:负责安排已有模块的顺序,并告知建造类开始建造.

1.2. 使用场景:

1.相同方法,不同执行顺序,产生不同的事件结果时. 2.多个部件或零件都可以装配到一个对象中,但是产生的运行结果又不相同时,可以使用该类. 3.产品类非常复杂,或者产品类中的调用顺序不同产生了不同的效能,这个时候使用建造者模式非常合适.

1.3. 实例

产品抽象类

public abstract class CarModel{
    private ArrayList<String> sequence = new ArrayList<String>();
    protected abstract void start();  //启动
    protected abstract void stop();   //停车
    protected abstract void alarm();  //喇叭
    protected abstract void engineBoom(); //引擎
    final public void run(){
        for(String tag:sequence){
            switch(tag.toLowerCase()){
                case "start" :
                    this.start();
                    break;
                case "stop" :
                    this.stop();
                    break;
                case "alarm" :
                    this.alarm();
                    break;
                case "engineBoom" :
                    this.engineBoom();
                    break;
            }
        }
    }


    final public void setSequence(ArrayList<String> sequence){
        this.sequence = sequence;
    }
}

产品实现类

public class BenzModel extends CarModel{
    protected void start(){
        system.out.println("奔驰启动");
    }
    protected void stop(){
        system.out.println("奔驰停止");
    }
    protected void alarm(){
        system.out.println("奔驰喇叭");
    }
    protected void engineBoom(){
        system.out.println("奔驰引擎");
    }
}

public class BMWModel extends CarModel{
    protected void start(){
        system.out.println("宝马启动");
    }
    protected void stop(){
        system.out.println("宝马停止");
    }
    protected void alarm(){
        system.out.println("宝马喇叭");
    }
    protected void engineBoom(){
        system.out.println("宝马引擎");
    }
}

抽象建造者

public abstract class CarBuilder{
    public abstract void setSequence(ArrayList<String> sequence);
    public abstract CarModel getCarModel();
}

具体建造者

public BenzBuilder extends CarBuilder{
    private BenzModel benz= new BenzModel();
    public CarModel getCarModel(){
        return this.benz;
    }
    public void setSequence(ArrayList<String> sequence){
        benz.setSequence(sequence);
    }
}

public BMWBuilder extends CarBuilder{
    private BMWModel bmw= new BMWModel();
    public CarModel getCarModel(){
        return this.bmw;
    }
    public void setSequence(ArrayList<String> sequence){
        this.bmw.setSequence(sequence);
    }
}

导演类

public class Director{
    private ArrayList<String> sequence = new ArrayList<String>();
    private BenzBuilder benzBuilder = new BenzBuilder();
    private BMWBuilder bmwBuilder = new BMWBuilder();
    public BenzModel getABenzModel(){
        this.sequence.clear();
        this.sequence.add("start");
        this.sequence.add("stop");
        this.benzBuilder.setSequence(sequence);
        return (BenzModel)this.benzBuilder.getCarModel();
    }
        public BenzModel getBBenzModel(){
        this.sequence.clear();
        this.sequence.add("engineBoom");
        this.sequence.add("start");
        this.sequence.add("stop");
        this.benzBuilder.setSequence(sequence);
        return (BenzModel)this.benzBuilder.getCarModel();
    }
        public BMWModel getCBMWModel(){
        this.sequence.clear();
        this.sequence.add("alarm");
        this.sequence.add("start");
        this.sequence.add("stop");
        this.bmwBuilder.setSequence(sequence);
        return (BMWModel)this.bmwBuilder.getCarModel();
    }
        public BMWModel getDBMWModel(){
        this.sequence.clear();
        this.sequence.add("start");
        this.bmwBuilder.setSequence(sequence);
        return (BMWModel)this.bmwBuilder.getCarModel();
    }
}