Peter Lawrey writes about high-performance Java, covering memory use, off-heap data, concurrency and low-latency techniques.
Commenters recommend it as a good JVM performance blog and link posts on off-heap memory with Unsafe, Java myths and using enums as state machines.
from 2008. slide 25:
experiments on a sampling of different JVMs.
More recent :
http://vanillajava.blogspot.com/2011/07/java-getting-size-of-object.html
http://vanillajava.blogspot.com/2011/07/java-how-much-memory-do-different.html
http://kohlerm.blogspot.com/2008/10/knowledge-about-much-memory-things-need.html
http://kohlerm.blogspot.com/2009/02/how-to-really-measure-memory-usage-of.html
http://marxsoftware.blogspot.com/2011/12/estimating-java-object-sizes-with.html
(i have zillions bookmarks on this)
http://dorophone.blogspot.com/ ;; elisp/picolisp stuff. monads, sexp, fexpr. inspiring.
http://okmij.org/ftp/ ;; general cs ftw. too deep.
http://john.freml.in/ ;; nice http server perf in clisp.
http://www.learningclojure.com/ ;; get the most of clojure in terms of cpu cycles. refreshing.
http://vanillajava.blogspot.com/ ;; perf, lo-level details about java. refreshing.
btw, swegr ~= hacker ?
I (as a Java developer) use state machines often - and know other developers who do same too. I use mostly enums (though there are other ways of achieving it), as explained in this post:
Java Secret: Using an enum to build a State machine: http://vanillajava.blogspot.com/2011/06/java-secret-using-enum-as-state-machine.html
Its a content farm, probably to count ad impressions or some other BS. This is the original (from the bottom of the article):
http://vanillajava.blogspot.com/2011/06/java-secret-using-enum-as-state-machine.html
I agree, avoiding GC is paramount. You can do this in Java by discarding less objects. http://vanillajava.blogspot.com/2011/06/how-to-avoid-garbage-collection.html
An interesting post on c++ like memory management in java:
http://vanillajava.blogspot.ca/2014/01/sunmiscunsafe-and-off-heap-memory.html?q=unsafe