Question

I am working on a project that is going on for several months now.
Suddenly when compiling we get the error:

Note: Some input files use unchecked or unsafe operations
Note: Recompile with -Xlint:unchecked for details.

After adding the -Xlint the above message disappear but the only error we get is:

[javac] 1 error

There are however about 45 warning. most of them not new.
Could it be that there is some new warning that I missed that cause the compilation to fail?

Edit:
I forgot to mention that the project builds properly on eclipse.
once a week we build using ant to product a version for the server.
I just want to know if there is a way to pin point the problem otherwise I guess I would have to review last 30 commits or go fix warning by warning.

Edit 2:
Problem fixed. I am not sure what it was exactly but I suspect that editing the my module.gwt.xml using external editor which might have miss-guessed the file encoding, inserted some non-visible characters with a wrong encoding which in turn caused the compiler to give an error w/o a proper description. (maybe I don’t know)

So what lessons should I take from this? handle all warning? (not sure that is always possible.)
using a jenkins? (as @Jayan suggested) the project manager would never approve investing time on such things in my company.

Answer 1

This error normally appears when you use a deprecated version of a class that now takes a Generic parameter. For example, in Java 6 and earlier, JList treated everything as Objects, and it was up to the programmer to cast everything correctly. In Java 7, JList is now JList<E>, with the parameter being the type of Objects contained in the list. JList (without generics) will still work, but you will get an error like the one you are experiencing.

EDIT: The reason, by the way, that these operations are considered unsafe is that, without the generics, types cannot be compared at compile time, and must be checked at runtime.