Questions about using `assert` in Java

[Daohan Qu]

Hi Alan,

> You will find places in the JDK code, esp. in performance critical code,
> where assertions are commented out. The reason is that asserts, even if
> disabled, increase the method size and can impact inlining by the
> compiler at run-time. So while useful when debugging some issue in such
> code, they are commended out to avoid increasing the method size.

Thanks a bunch! I didn't realize this before!

> Asserts are very useful during development or when testing, e.g. the JDK
> tests run with -esa and can periodically help catch issues when testing
> a change.

Indeed. But I am a little bit curious: unlike C/C++, which enables assert​
by default (You could define NDEBUG​ to disable it during compilation),
Java disables assert​ by default. I wonder why the language designers
made such a decision. Is it for backward compatibility? IMHO, enabling it by
default might potentially increase its usage among developers.

Regards,
Daohan
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