设计模式18---解释器模式

解释器模式常用的场景是计算器，或者说公式。

也就是说解释的符号满足公式的元素，而client端把每个元素的内容代换掉就可以。

package com.jayfulmath.designpattern.experssion;



import java.util.HashMap;



public abstract class Experssion {

    //解析公式和数值,其中var中的key值是是公式中的参数，value值是具体的数字

    public abstract int interpreter(HashMap<String, Integer> var);

}

package com.jayfulmath.designpattern.experssion;



import java.util.HashMap;



public class VarExperssion extends Experssion {



    private String key;

    @Override

    public int interpreter(HashMap<String, Integer> var) {

        System.out.println("VarExperssion interpreter key:"+key);

        return var.get(key);

    }

    public VarExperssion(String key) {

        super();

        this.key = key;

    }

    

    

}

public abstract class  SymbolExperssion extends Experssion {



    Experssion left;

    Experssion right;

    public SymbolExperssion(Experssion left, Experssion right) {

        super();

        this.left = left;

        this.right = right;

    }

    

}

import java.util.HashMap;



public class AddExperssion extends SymbolExperssion {



    public AddExperssion(Experssion left, Experssion right) {

        super(left, right);

        

    }



    @Override

    public int interpreter(HashMap<String, Integer> var) {

        return super.left.interpreter(var)+super.right.interpreter(var);

    }

    

}

package com.jayfulmath.designpattern.experssion;



import java.util.HashMap;



public class SubExperssion extends SymbolExperssion {



    public SubExperssion(Experssion left, Experssion right) {

        super(left, right);

        

    }



    @Override

    public int interpreter(HashMap<String, Integer> var) {

        return super.left.interpreter(var) - super.right.interpreter(var);

    }



}