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);
    }

}