A Healthy diet for your Java application
summary
Diagnoses OutOfMemory by insisting on heap dumps and analyzing GC roots in VisualVM, showing byte[] and object arrays often hold 90%+ of retained size. Finds concrete causes: mutable or wrongly implemented equals/hashCode bug that inflates HashMap keys, non-static inner classes that retain huge outer objects, and thread-local retention that never unset values on pooled threads. Demonstrates fixes and rules, and reports memory drop from ~3.0 GB to ~1.2 GB after cleanup.
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chapters (15)
- 0:00Introduction and speaker intro
- 2:14Why care about Java memory
- 5:27Identifying memory problems
- 9:43Measuring and monitoring memory
- 13:36Stack traces vs heap dumps
- 15:01Analyzing heap dumps with VisualVM
- 17:48Static fields and garbage collection
- 22:39Equals and hashCode contract
- 29:20Inner classes and memory leaks
- 33:37Thread locals and memory
- 35:25Memory leaks vs memory footprint
- 40:25Preventing future memory issues
- 44:38Healthy diet summary
- 45:22Outcome of the investigation
- 47:29Q&A session
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