437

In particular, is there a standard Exception subclass used in these circumstances?

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2
  • Is it appropriate to use when a class does not implement a method, but child classes may do so? In other words, to have an abstract method in a non-abstract class. Commented Oct 7, 2013 at 22:24
  • @SergeyOrshanskiy It's useful for when, depending on how you construct an object, you need to create an anonymous class that implements an interface in order to instantiate a member variable, but you don't want it to be used. If you set it to null and you accidentally used it (or someone else did) you would get NullPointerExceptions which are less obvious than UnsupportedOperationExceptions in this case. Just an example. Commented Apr 24, 2014 at 15:52

5 Answers 5

Reset to default
594

From the Java documentation:

Thrown to indicate that the requested operation is not supported.

― java.lang.UnsupportedOperationException

Example usage:

throw new UnsupportedOperationException("Feature incomplete. Contact assistance.");
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4 Comments

@JarrodRoberson OK, that statement should really be removed from the class documentation in that case. The exception does seem to be used by other packages. I guess if Oracle does so, then so should we. I'll file a bug report.
Be aware this is an unchecked RuntimeException. You will get no feedback or assistance in handling these exceptions during compile time. If this is used for a stubbed method or a work-in-progress you should use some kind of checked exception.
You might wanna do it like this to indicate, that the implementation is yet to come: throw new java.lang.UnsupportedOperationException("Not implemented yet."); //todo implement
It can be puzzling to find public API methods that don't implement logic yet and return null value. I prefer having a method returning UnsupportedOperationException. I use this myself and rewrite any existing code with this exception, when obviously no logic was implemented.
262

Differentiate between the two cases you named:

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3 Comments

I am going with this, because it seems reasonable to me. "Yet" or "never" indicated by the Exception gives an idea on how to react on this.
#s 1 or 2 are greatly preferable in practice. #3 does capture the semantic distinction between "not supported" and "not implemented", but having a separate class makes it easier to do a quick search to verify that you haven't forgotten to implement anything you should before committing.
#3 is best for not implemented methods as it doesn't require a third party library or additional work, even if it is commons-lang.
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If you create a new (not yet implemented) function in NetBeans, then it generates a method body with the following statement:

throw new java.lang.UnsupportedOperationException("Not supported yet.");

Therefore, I recommend to use the UnsupportedOperationException.

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16

If you want more granularity and better description, you could use NotImplementedException from commons-lang

Warning: Available before versions 2.6 and after versions 3.2 only.

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7

The below Calculator sample class shows the difference

public class Calculator() { int add(int a , int b){ return a+b; } int dived(int a , int b){ if ( b == 0 ) { throw new UnsupportedOperationException("I can not dived by zero, not now not for the rest of my life!") }else{ return a/b; } } int multiple(int a , int b){ //NotImplementedException from apache or some custom excpetion throw new NotImplementedException("Will be implement in release 3.5"); } }
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