Java API break
backwards-compatibility, java
Solution
Yes, you're breaking the contract of the interface by throwing an exception when C1 doesn't occur.
As a rule of thumb, the vaguer the interface contract, the easier it is not to break :) If the interface isn't defined in terms of an explicit C1, but in more general terms, that gives a lot more flexibility.
Problem
I have the following API: ``` public interface MyApi { /** * Performs some stuff. * @throws MyException if condition C1 */ public void method() throws MyException; } ``` I am now performing the following modification in my API implementation ``` public class MyApiImpl { public void method() throws MyException { if (C1) { throw new MyException("c1 message"); } ... } } ``` is replaced by : ``` public class MyApiImpl { public void method() throws MyException { if (C1) { throw new MyException("c1 message"); } else if (c2) { throw new MyException("c2 message"); } ... } } ``` Do you consider this as an API breakage ? Client's code will still compile but method contract defined by the API javadoc is no more respected since MyExcepiton is thrown by a "new" condition. If only my API jar file is updated, clients application will still work but depending on the way clients catch the exception the application behavior can change a lot. What's your point of view on that ?