Out Of MemoryOut Of MemoryAnalyze Your Java HeapAnalyze Your Java Heap

GC silver bullet

Unreferenced memory cleared

Fragmentation cleanup

Incorrect understanding of data / structures

Packratting

Data / Structures

Primitives vs Objects

Byte vs byte

Overhead of structure

LinkedList vs ArrayList

JVM settings

UseCompressedOops, UseCompressedStrings

Packratting

Unintentionally storing data

Unbounded caches

Classloaders

Containers / plugins

ThreadLocals

Statics

What now

Avoid situation ;-)

Snapshot

-XX:+HeapDumpOnCtrlBreak

-XX:+HeapDumpOnOutOfMemoryError

jmap -dump:format=b,file=snapshot.bin pid

jconsole

MATEclipse Memory Analyzer

Wizards

Compare

Explore

Query

Can be large

Takes time to produce

Can contain sensitive information

Watch out

LInks

MAT http://www.eclipse.org/mat/

jconsole http://docs.oracle.com/javase/7/docs/technotes/tools/share/jconsole.html

jmap http://docs.oracle.com/javase/7/docs/technotes/tools/share/jmap.html

jstat http://docs.oracle.com/javase/7/docs/technotes/tools/share/jstat.html

Java API http://www.eclipse.org/forums/index.php/t/243401/