On Mon, 15 Jun 2026 17:26:59 GMT, Jaikiran Pai <[email protected]> wrote:
>> src/java.base/share/classes/java/lang/Object.java line 314:
>>
>>> 312: * <div class="preview-comment">
>>> 313: * If this object is a {@linkplain
>>> java.util.Objects#hasIdentity value object},
>>> 314: * it does does not have a monitor, an {@code
>>> IllegalMonitorStateException} is thrown.
>>
>> Suggestion:
>>
>> * it does not have a monitor, an {@code
>> IllegalMonitorStateException} is thrown.
>
> Several places in the API specifications, specify that:
>
>> Use of value class instances for synchronization, mutexes, or with
>> {@linkplain java.lang.ref.Reference object references} results in
>> {@link IdentityException}
>
> whereas here, in these wait(), notify() etc... APIs, which are closer to
> synchronization semantics, a `IllegalMonitorStateException` gets thrown for
> value objects. Is there a reason why we don't throw a `IdentityException`
> from these APIs too? I haven't followed Valhalla development, so if this was
> already discussed, please point me to it.
While at it, I did a quick experiment with value object:
jshell> Object o = Integer.parseInt("42")
o ==> 42
jshell> o.wait()
| Exception java.lang.IllegalMonitorStateException: java.lang.Integer
| at Object.wait0 (Native Method)
| at Object.wait (Object.java:433)
| at Object.wait (Object.java:387)
| at (#15:1)
So the `IllegalMonitorStateException` thrown merely states the class name of
the object but doesn't tell anything more. Whereas for a identity object (like
a String), it throws:
jshell> Object s = new String("")
s ==> ""
jshell> s.wait()
| Exception java.lang.IllegalMonitorStateException: current thread is not owner
| at Object.wait0 (Native Method)
| at Object.wait (Object.java:433)
| at Object.wait (Object.java:387)
| at (#17:1)
is a bit more informative why it's an illegal monitor state.
Could the IllegalMonitorStateException exception message for value objects be
improved to state something like:
Exception java.lang.IllegalMonitorStateException: instance of java.lang.Integer
value class
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/31123#discussion_r3415375403
