Enrich the Lock interface

[John Hendrikx]

I couldn't find a discussion on openjdk, but for those interested (and 
to save others some searching) there is a JBS ticket:

https://bugs.openjdk.org/browse/JDK-8025597

--John

On 21/08/2023 14:37, Pavel Rappo wrote:
> This is suggested every once in a while. I appreciate that openjdk mailing lists are not easily searchable, but with a bit of skill, you could find a few previous discussions on the topic.
>
> This has also been discussed on concurrency-interest (at cs.oswego.edu <http://cs.oswego.edu/>), a dedicated mailing list for concurrency in Java. Sadly, that list has been defunct for quite some time now.
>
> -Pavel
>
>> On 21 Aug 2023, at 13:18, Albert Attard <albertattard at gmail.com> wrote:
>>
>> Hello.
>>
>> I hope all is well.
>>
>> Do you believe it is a bad idea to enrich the Lock interface with a set of default methods that safely release the lock once ready?
>>
>> Consider the following (dangerous) example.
>>
>> final Lock lock = new ReentrantLock ();
>> lock.lock();
>> /* Code that may throw an exception */
>> lock.unlock();
>>
>> This example will never release the lock if an exception is thrown, as the programmer didn’t wrap this up in a try/finally.
>>
>> Adding a default method within the Lock interface, called withLock(Runnable) for example or any better name, would streamline this, as shown next.
>>
>> default void withLock(final Runnable runnable) {
>>      requireNonNull(runnable, "Cannot run a null");
>>      lock();
>>      try {
>>          runnable.run();
>>      } finally {
>>          unlock();
>>      }
>> }
>>
>> The caller can now simply change the above example into the following, without having to worry about this.
>>
>> final Lock lock = new ReentrantLock ();
>> lock.withLock(() -> {
>>    /* Code that may throw an exception */
>> });
>>
>> We can have more variants of these default methods, as shown next.
>>
>> default <T> T getWithLock(final Supplier<T> supplier) {
>>      requireNonNull(supplier, "The supplier cannot be null");
>>      lock();
>>      try {
>>          return supplier.get();
>>      } finally {
>>          unlock();
>>      }
>> }
>>
>> Any thoughts?
>>
>> With kind regards,
>> Albert Attard