行为型模式-中介者模式

Posted 2021-01-28 liunianfeiyu

　　行为型模式又可以分成以下四类：第一类：通过父类与子类的关系进行实现。第二类：两个类之间。第三类：类的状态。第四类：通过中间类

　　命令模式属于第四类，通过中间类

　　我们来看一下两个类之间是如何通过中间类来相互影响的

package behavior.pattern.intermediator.mediator;

public abstract class AbstractColleague {
    protected float number;  
      
    public float getNumber() {  
        return number;  
    }  
  
    public void setNumber(float number){  
        this.number = number;  
    }  
    //注意这里的参数不再是同事类，而是一个中介者  
    public abstract void setNumber(float number, AbstractMediator am); 
}

package behavior.pattern.intermediator.mediator;

public class ColleagueA extends AbstractColleague {
    public void setNumber(float number, AbstractMediator am) {  
        this.number = number;  
        am.AaffectB();  
    }
}

package behavior.pattern.intermediator.mediator;

public class ColleagueB extends AbstractColleague {
    @Override  
    public void setNumber(float number, AbstractMediator am) {  
        this.number = number;  
        am.BaffectA();  
    }
}

package behavior.pattern.intermediator.mediator;

public abstract class AbstractMediator {
    protected AbstractColleague A;  
    protected AbstractColleague B;  
      
    public AbstractMediator(AbstractColleague a, AbstractColleague b) {  
        A = a;  
        B = b;  
    }  
  
    public abstract void AaffectB();  
      
    public abstract void BaffectA();
}

package behavior.pattern.intermediator.mediator;

import org.apache.commons.math3.util.Precision;

public class Mediator extends AbstractMediator {

    public Mediator(AbstractColleague a, AbstractColleague b) {  
        super(a, b);  
    }  
  
    //处理A对B的影响  
    public void AaffectB() {  
        float number = A.getNumber();  
        B.setNumber(number*10);  
    }  
  
    //处理B对A的影响  
    public void BaffectA() {  
        float number = B.getNumber();
        A.setNumber(Precision.round(number/10, getDecimalDigit(number) + 1));  
    }
    
    private int getDecimalDigit(float number)
    {
        int digit = 0;
        String numberString = String.valueOf(number);
        if(numberString.indexOf(".") != -1)
        {
            digit = numberString.substring(numberString.indexOf(".") + 1).length();
        }
        else
        {
            digit = 0;
        }
        return digit;
    }
}

　　测试代码

package behavior.pattern.intermediator.mediator;

public class Client {
    public static void main(String[] args){  
        AbstractColleague collA = new ColleagueA();  
        AbstractColleague collB = new ColleagueB();  
          
        AbstractMediator am = new Mediator(collA, collB);  
          
        System.out.println("==========通过设置A影响B==========");  
        collA.setNumber(1001, am);  
        System.out.println("collA的number值为："+collA.getNumber());  
        System.out.println("collB的number值为A的10倍："+collB.getNumber());  
        
        System.out.println("==========通过设置B影响A==========");  
        collB.setNumber(10.02F, am);  
        System.out.println("collB的number值为："+collB.getNumber());  
        System.out.println("collA的number值为B的0.1倍："+collA.getNumber());  
          
    }
}

　　运行结果