Extending checkstyle to detect objetc comparison with == operator.

Hello,

I am currently working on a project which was partly developped by java newbies and we encountered several bugs which had for root cause object comparison using == instead of .equals().

Those objects (1 class + 1 subclass) are from a cached repository so they would work for unit testing but would start showing erratic behavior after cache invalidations.

I wanted to use checkstyle on this project to mainly improve code quality and enforce standards but i would also like to extend it to detect those erroneous comparisons.

Bad code would look like

RepositoryItem item1 = ...
RepositoryItem item2 = ...

if (item1 == item2) {
    doCriticalStuff();
}

Is it possible to extend checkstyle to detect this ?

I have started working on a check class (largely inspired from StringLiteralEquality) but i am unsure on how to check the instance type. I have the AST items ready (aka. getFirstChild() + getFirstChild().nextSibling() ). But i dont know how to proceed to detect that they are instances of RepositoryItem or one of their subclass.

I would appreciate any help on this matter.


Thanks in advance,
Benoit.

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