----- Mail original -----
> De: "Ivan Gerasimov" <ivan.gerasi...@oracle.com>
> À: "Krystal Mok" <rednaxel...@gmail.com>, "core-libs-dev"
> <core-libs-dev@openjdk.java.net>
> Envoyé: Samedi 3 Septembre 2016 12:23:28
> Objet: Re: A bit of sugar for j.u.c.locks with try-with-resources?
> Hi Krystal!
>
> On 03.09.2016 5:41, Krystal Mok wrote:
>> Hi core-libs developers,
>>
>> I mostly live down in the VM world, but recently I've been playing with
>> j.u.c.locks a bit, and saw that there's an opportunity to retrofit the API
>> with the try-with-resources syntax. I wonder if anybody has brought this
>> topic up before; apologies if there had been.
>>
>> >From the JavaDoc of j.u.c.l.ReentrantLock, the following is a typical usage:
>>
>> class X {
>> private final ReentrantLock lock = new ReentrantLock();
>> // ...
>>
>> public void m() {
>> lock.lock(); // block until condition holds
>> try {
>> // ... method body
>> } finally {
>> lock.unlock()
>> }
>> }
>> }
> It could be written as
> public void m() {
> lock.lock(); // block until condition holds
> try (Closeable unlocker = lock::unlock) {
> // ... method body
> }
> }
>
> This would save a couple of lines of code.
but it does an allocation (if the escape analysis fails),
i think it's better to wait for proper value types :)
>
> With kind regards,
> Ivan
regards,
Rémi
>
>> The try...finally construction really pops out as a try-with-resources
>> candidate.
>>
>> So what if we retrofit that with something like:
>>
>> class X {
>> private final ReentrantLock lock = new ReentrantLock();
>> // ...
>>
>> public void m() {
>> try (lock.lock()) { // block until condition holds
>> // ... method body
>> } // automatic unlock at the end
>> }
>> }
>>
>> Assuming lock.lock() returns a temporary wrapper object (let's call it a
>> "Locker" for this discussion), where Locker implements AutoCloseable, and
>> its close() method calls lock.unlock().
>> That'll make the API look and feel quite similar to the built-in
>> "synchronized () { ... }" syntax. With escape analysis and scalar
>> replacement implemented correctly in the VM, this temporary Locker object
>> wouldn't incur much (or any) runtime cost after optimized JIT'ing, so it
>> feels like a pure win to me.
>>
>> What do you think?
>>
>> Best regards,
>> Kris (OpenJDK username: kmo)
