How to quickly determine if a method is overridden in Java

Question

There is a possible optimization I could apply to one of my methods, if I can determine that another method in the same class is not overridden. It is only a slight optimization, so reflection is out of the question. Should I just make a protected method that returns whether or not the method in question is overridden, such that a subclass can make it return true?

Answer 1

I wouldn't do this. It violates encapsulation and changes the contract of what your class is supposed to do without implementers knowing about it.

If you must do it, though, the best way is to invoke

class.getMethod("myMethod").getDeclaringClass(); 

If the class that's returned is your own, then it's not overridden; if it's something else, that subclass has overridden it. Yes, this is reflection, but it's still pretty cheap.

I do like your protected-method approach, though. That would look something like this:

public class ExpensiveStrategy {   public void expensiveMethod() {     // ...     if (employOptimization()) {       // take a shortcut     }   }    protected boolean employOptimization() {     return false;   } }  public class TargetedStrategy extends ExpensiveStrategy {   @Override   protected boolean employOptimization() {     return true; // Now we can shortcut ExpensiveStrategy.   } } 

Answer 2

Well, my optimization is a small yield on a case-by-case basis, and it only speeds things a lot because it is called hundreds of times per second.

You might want to see just what the Java optimizer can do. Your hand-coded optimization might not be necessary.

If you decide that hand-coded optimization is necessary, the protected method approach you described is not a good idea because it exposes the details of your implementation.

Answer 3

How many times do you expect the function to be called during the lifetime of the program? Reflection for a specific single method should not be too bad. If it is not worth that much time over the lifetime of the program my recommendation is to keep it simple, and don't include the small optimization.

Jacob