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== and != on wrappers

Mauricio Bonetti

Joined: Aug 25, 2008
Posts: 4

Solving some questions about wrappers I got really in doubt on how to use == and != operators.

I've read K&B 5 chapter about wrappers but the portugueese translation drove me nuts !

What do they compare ? They look if the reference instances the same object ?? Is that ??
Henry Wong

Joined: Sep 28, 2004
Posts: 18113


If both sides are wrappers (meaning instances), then it is comparing the references. The two sides are equal if they are the same object.

If only one side is a wrapper, then autoboxing will unbox the wrapper -- and it is the values that will be compared. The two sides are equal if they represent the same value.


Books: Java Threads, 3rd Edition, Jini in a Nutshell, and Java Gems (contributor)
It is sorta covered in the JavaRanch Style Guide.
subject: == and != on wrappers
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