Re: Using enums to avoid using switch/if

"Karl Uppiano" <>
Wed, 10 Jun 2009 05:14:45 GMT
"Philipp" <> wrote in message

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{
   public double eval(double a, double b) {
     return a + b;

 private static Map<String, Operator> operators = new HashMap<String,
   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);

Or you can use the valueOf method built into enums, to return the enum,
given the name that was used to define the enum. It effectively implements
the mapping for you.,

An example is given towards the bottom of this article:

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