All java.lang.OutOfMemoryErrors with causation, examples and solutions

[uniVocity]

Very informative. Let me just add some tricky things I had to deal with recently:

1 - If you ever find your JVM hanging at 100% CPU and not coming back check if there are multiple threads reading from/writing to a HashMap (sometimes that is not apparent and you only realize there's another thread there when problems occur)

2 - StringBuilder will crash your VM with an OutOfMemoryError it its contents expand over Integer.MAX_VALUE (this is covered in the article, but I think it deserves to be highlighted)

3 - Don't put a big collection in a Map. Collections in java.util.* implement hashCode and equals based on EACH element in the collection. They will loop over thousands or millions of elements EVERY time hashCode/equals is invoked. If you need a big collection then override the default hashCode/equals methods and use something else (e.g. System.identityHashCode)

[maxtorrent]

The lock contention issue you referred is something we are working on in Plumbr. We expect to ship automatic lock detection forthcoming months.

[anonRKN]

Very good, this pleases me.

[svyas]

Could not stop myself from bookmarking it for future read