CODEWITHSUNDEEP
javadesign-patterns
Lola
Lola

Reputation: 145

Refactoring two similar classes in java

I have two classes in Java which basically act the same but one represents a multiplier and the other represents a divider. I want to create a parent class which both of them can extend but I don't know how to do that. What should I pass to the parent class? this are both of the classes I have created:

import java.util.HashMap;

public class Divide extends Operator {
    
    private String DIVIDE = " / ";
    
    public Divide(Expression leftExp, Expression rightExp){
        super(leftExp,rightExp);
    }
    
    /*
     * We assume that our divider is not zero. If it is, then we can handle it with exceptions*
     */
    
    @Override
    public float calculate(HashMap<String,Integer> map) {
        return this.leftExp.calculate(map) / this.rightExp.calculate(map);
    }
    
    private String isWithParentheses(Expression exp) {
        return exp.getClass().getSimpleName() == "Variable" || 
                exp.getClass().getSimpleName() == "Number" ? 
                        exp.toString() : "(" + exp.toString() + ")";
    }
    
    @Override
    public String toString() {
        String leftExpString = this.isWithParentheses(this.leftExp);
        String rightExpString = this.isWithParentheses(this.rightExp);
        
        return leftExpString + DIVIDE + rightExpString;
    }
    
    @Override
    public void print() {
        System.out.println(this.toString());
        
    }
    
}


import java.util.HashMap;

public class Multiply extends Operator {
    
    private String MULTIPLY = " * ";
    
    public Multiply(Expression leftExp, Expression rightExp){
        super(leftExp,rightExp);
    }
    
    @Override
    public float calculate(HashMap<String,Integer> map) {
        return this.leftExp.calculate(map) * this.rightExp.calculate(map);
    }
    
    private String isWithParentheses(Expression exp) {
        return exp.getClass().getSimpleName() == "Variable" || 
                exp.getClass().getSimpleName() == "Number" ? 
                        exp.toString() : "(" + exp.toString() + ")";
    }
     
    @Override
    public String toString() {
        String leftExpString = this.isWithParentheses(this.leftExp);
        String rightExpString = this.isWithParentheses(this.rightExp);
                
        return leftExpString + MULTIPLY + rightExpString;
    }
    
    @Override
    public void print() {
        System.out.println(this.toString());
        
    }
    
}

Upvotes: 0

Views: 200

Answers (1)

Andy Turner
Andy Turner

Reputation: 140544

Pass the symbol and the math operation to the super constructor:

public Multiply(Expression leftExp, Expression rightExp){
    super(leftExp,rightExp, " * ", (a, b) -> a * b);
}

and

public Divide(Expression leftExp, Expression rightExp){
    super(leftExp,rightExp, " / ", (a, b) -> a / b);
}

Then you can store these parameters in appropriate fields, and use them in the methods, e.g.

return leftExpString + symbol + rightExpString;

return fn.apply(this.leftExp.calculate(map), this.rightExp.calculate(map));

Upvotes: 3

Related Questions