CODEWITHSUNDEEP
javaoopinheritanceinterface
ks2bmallik
ks2bmallik

Reputation: 184

Generic Java Code for performing arithmetic operations without using control logic

I am building a simple Calculator in Android. I have three parameters namely, firstNumber, secondNumber and operation to be performed. It can be easily done using if-else block, but as its not a good and scalable solution (considering I will add more features in future), I was trying to use Java OOPs features (interfaces or so).

I know its a very trivial problem, but being a beginner I am unable to do it.

// Common Interface
public interface ComputationInterface {
    public String compute(int firstNum,
                        int secondNum);
}

// Addition
public class Add implements ComputationInterface{
    public String compute(int firstNum, int secondNum){
    int sum = firstNum + secondNum;
    return Integer.toString(sum);
   }
}

// Subtraction
public class Divide implements ComputationInterface{
    public String compute(int firstNum, int secondNum){
        if(secondNum == 0)
            return "Division by ZERO undefined";
        int quotient = firstNum/secondNum;
        int remainder = firstNum % secondNum;
        return String.format("%d R: %d", quotient, remainder);
    }
}

// Multiplication
public class Multiply implements ComputationInterface{
    public String compute(int firstNum, int secondNum){
        int resultNum = firstNum * secondNum;
        return Integer.toString(resultNum);
    }
}

// Division
public class Subtract implements ComputationInterface{
    public String compute(int firstNum, int secondNum){
        int diffNum = firstNum - secondNum;
        return Integer.toString(diffNum);
    }
}


/* Code Snippet from where I have to call above operations  */ 

private static final int ADD = 1;
private static final int SUB = 2;
private static final int MUL = 3;
private static final int DIV = 4;

/** 
 * 'operation' param corresponds to one of the four arithmetic
 * operations listed above.
 */
public void performCalculation(int argumentOne, int argumentTwo, int operation){
   // TODO: Help Needed
}

EDIT

The solution I am looking for is I will make a call on some Java object, passing three parameters to it, as below

String result = SomeJavaObject.doCompuation(int argumentOne, int argumentTwo, 
                                          int operation);

Moreover, I want the solution to be scalable enough, so I can easily add new features like log, power etc. by creating new java classes/interfaces etc.

Upvotes: 0

Views: 562

Answers (2)

GhostCat
GhostCat

Reputation: 140427

One thing you can do - change your interface to:

public int compute(int... arguments)

  1. That allows you to invoke with any number of arguments, 0, 1, 2, ... n. (probably you have to think a while to define what compute() or compute(1) should result in; but once implement, compute(1,2,3) doesn't require additional coding!
  2. Return an int. There is absolutely no point in doing arithmetical computations and return the result as String. Such changes of "format" should only occur in the end; like for some kind of "print out" functionality. But while "computing", dont waste "energy" on turning stuff into strings. As probably very soon, you might want to use the result of one call to compute() ... as argument to another call!

Upvotes: 0

Peter Lawrey
Peter Lawrey

Reputation: 533500

I have used an enum for this in the past.

public enum Ops implements ComputationInterface {
    Add('+') {
       public Object compute(long firstNum, long secondNum){
           return firstNum + secondNum;
       }
   }, 
   Subtract('-') {
      ...
   },
   Multiply('*') {

   },
   Divide('/') {
       public Object compute(long firstNum, long secondNum){
           if (secondNum == 0)
                return "Division by ZERO undefined";
           long quotient = firstNum / secondNum;
           long remainder = firstNum % secondNum;
           return remainder == 0 ? quotient : String.format("%d R: %d", quotient, remainder);
      }
   }
}

Upvotes: 1

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