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Why Many Return Statements Are a Bad Idea in OOP

  • Kiev, Ukraine
  • modified on
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OOPoop java

This debate is very old, but I have something to say too. The question is whether a method may have multiple return statements or always just one. The answer may surprise you: In a pure object-oriented world, a method must have a single return statement and nothing else. Yes, just a return statement and that's it. No other operators or statements. Just return. All arguments in favor of multiple return statements go against the very idea of object-oriented programming.

This is a classical example:

public int max(int a, int b) {
  if (a > b) {
    return a;
  }
  return b;
}

The code above has two return statements, and it is shorter than this one with a single return:

public int max(int a, int b) {
  int m;
  if (a > b) {
    m = a;
  } else {
    m = b;
  }
  return m;
}

More verbose, less readable, and slower, right? Right.

This is the code in a pure object-oriented world:

public int max(int a, int b) {
  return new If(
    new GreaterThan(a, b),
    a, b
  );
}

What do you think now? There are no statements or operators. No if and no >. Instead, there are objects of class If and GreaterThan.

This is a pure and clean object-oriented approach.

However, Java doesn't have that. Java (and many other pseudo OOP languages) gives us operators like if, else, switch, for, while, etc. instead of giving built-in classes, which would do the same. Because of that, we continue to think in terms of procedures and keep talking about whether two return statements are better than one.

If your code is truly object-oriented, you won't be able to have more than one return. Moreover, you will have nothing except a return in each method. Actually, you will have only two operators in the entire software—new and return. That's it.

Until we're there, let's stick with just one return and at least try to look like pure OOP.