mjlee - Developer IT

is guava-libraries available in maven repo?

- by mjlee

I am looking to find guava-libraries in maven repository. It looks like guava is adding more features to google-collections library.

Iterables.find and Iterators.find - instead of throwing exception, get null

I'm using google-collections and trying to find the first element that satisfies Predicate if not, return me 'null'. Unfortunately, Iterables.find and Iterators.find throws NoSuchElementException when no element is found. Now, I am forced to do Object found = null; if ( Iterators.any( newIterator(...) , my_predicate ) { found = Iterators.find( newIterator(...), my_predicate ) } I can surround by 'try/catch' and do the same thing but for my use-cases, I am going to encounter many cases where no-element is found. Is there a simpler way of doing this?

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Java Annotations - Is there any helper library to read/process annotations?

- by mjlee

I start to use Java annotations heavily. One example is taking method with annotations and converting them into 'telnet'-based command-line command. I do this by parsing annotations and hook into jopt option parser. However, I do a lot of these manually. For example, Method parameter annotation processing.. Method method = ... //; Class[] parameters = method.getParamterTypes(); Annotation[][] annotations = method.getparamterAnnotations(); for( int i = 0; i < parameters.length; i++ ) { // iterate through the annotation , see if each param has specific annotation ,etc. } It is very redundant and tedious. Is there any opensource project that help processing Annotations?

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How do I prevent use of beta classes from google guava library?

- by mjlee

We have been using Google collections in the production for several months. We would like to start using guava for additional functions. However, I'm afraid to bring guava into our product stack b/c some developers may start to use 'beta' classes. We have various unit-tests in our code but at this point, I prefer not to include 'beta' class b/c it is subject to change in the future. Is there any easy way to do detect if the project includes any 'beta' guava classes?

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In ArrayBlockingQueue, why copy into ReentrantLock field into local final variable?

- by mjlee

In ArrayBlockingQueue, any method that requires lock will get set 'final' local variable before calling 'lock()'. public boolean offer(E e) { if (e == null) throw new NullPointerException(); final ReentrantLock lock = this.lock; lock.lock(); try { if (count == items.length) return false; else { insert(e); return true; } } finally { lock.unlock(); } } Is there any reason to set a local variable 'lock' from 'this.lock' when field 'this.lock' is final also. Additionally, it also set local variable of E[] before acting on. private E extract() { final E[] items = this.items; E x = items[takeIndex]; items[takeIndex] = null; takeIndex = inc(takeIndex); --count; notFull.signal(); return x; } Is there any reason for copying to local final variable?

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In ArrayBlockingQueue, why copy final member field into local final variable?

- by mjlee

In ArrayBlockingQueue, any method that requires lock will get set 'final' local variable before calling 'lock()'. public boolean offer(E e) { if (e == null) throw new NullPointerException(); final ReentrantLock lock = this.lock; lock.lock(); try { if (count == items.length) return false; else { insert(e); return true; } } finally { lock.unlock(); } } Is there any reason to set a local variable 'lock' from 'this.lock' when field 'this.lock' is final also. Additionally, it also set local variable of E[] before acting on. private E extract() { final E[] items = this.items; E x = items[takeIndex]; items[takeIndex] = null; takeIndex = inc(takeIndex); --count; notFull.signal(); return x; } Is there any reason for copying to local final variable?

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Queue implementation with blocked 'take()' but with eviction policy

- by mjlee

Is there an implementation with a blocking queue for take but bounded by a maximum size. However, when the maximum size is reached, instead of blocking, it will remove from the head. One usage is that if I have a very slow consumer, the system will not crash ( runs out of memory ) rather these message will be removed.

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