Re: Using enums to avoid using switch/if

You could also take the look-up approach (see below). This is also
possible with enums as Lew proposed them, using a Map instead of the
linear search in the fromString() method.
HTH Phil

import java.util.HashMap;
import java.util.Map;

public class ATest {

 static interface Operator{
   public double eval(double a, double b);
 }

 static class Add implements Operator{
   @Override
   public double eval(double a, double b) {
     return a + b;
   }
 }

 private static Map<String, Operator> operators = new HashMap<String,
Operator>();
 static{
   operators.put("+", new Add());
   // etc
 }

 public static void main(String[] args) {
   double a = 12.3;
   double b = 23.4;
   String opStr = "+";
   // instead of if/else
   Operator op = operators.get(opStr);
   // should probably check for null
   double result = op.eval(a, b);
   System.out.println("Result is " + result);
 }
}