alternative to if statement in java

Question

I am curious to see any alternative(s) to the regular if statements such as

if(x)
     do a;
if(y)
     do b;
if(z)
    do c;

so as you see all if statements are seperate and no else condition. Please notice that X Y Z are totally seperate conditions so switch wouldn't fit.

Answer 1

this is the most simple, readable yet effective solution. I would be surprised to see effective alternatives here.

EDIT

you can try to apply extract method several times:

doAIfX();
doBIfY();
doCifZ();

where methods are defined by:

void doAIfX() {
    if (!X) {
        return;
    }

    // do 'a'
}

Answer 2

it really depends on what x, y, z and a, b, c are. Sometimes if statements are more suitable. Sometimes polymorphism is more suitable.

Answer 3

The alternatives to if-else in Java are the switch statement and the conditional ternary (?:) operator, neither of which do exactly what you're asking (handle just an if with no else). The code you posted is the best way to do it, in my opinion.

Answer 4

Use polymorphism.

interface SomethingDoer {
    public void doSomething();
}

class ADoer implements SomethingDoer { ... }
class BDoer implements SomethingDoer { ... }
class CDoer implements SomethingDoer { ... }

public class Main {
     public static void main (String[] args) {
          SomethingDoer doer = new SomethingDoerFactory(args).getDoer();
          doer.doSomething();
     }
}

The if is not completely eliminated, but it is moved to SomethingDoerFactory. This solution is not applicable in all cases, but in some of them it is a very good alternative to multiple ifs.

Here is a nice talk about it:
http://misko.hevery.com/2008/12/08/clean-code-talks-inheritance-polymorphism-testing/

Answer 5

One "truely object oriented" answer would be to define an interface for "Rule" (with condition() and action() methods), create 3 implementations, stuff them into a collection, and then just iterate through them generically as in:

List<Rule> rules = .... ; // your 3 rules initialized here somehow
for(Rule r : rules) {
  if(r.condition()) {
    r.action();
  }
}

This makes a lot more sense if you have 300 rules/conditions rather than just 3.

Answer 6

You will need to have these if statements somewhere.

They can be refactored into other methods to keep the present method clean, as others have suggested. If you need to re-use this same set of if statements in a number of places, it might be possible use the Decorator Pattern.

Answer 7

Switch perhaps?

I can't think why you would want to replace it though.

Answer 8

It sounds like a perfect case for using closure. But for that you need groovy or something similar.