![Empty ArrayList is iniIalized with
Object array of size 10:
Object[] elementData = new Object[10];](https://image.slidesharecdn.com/javabehindthescenes-161213100342/85/Igor-Dmitriev-Java-behind-the-scenes-7-320.jpg)
![Analysed 670 Java heap dumps from different
Java programs to find out memory hogs.
Most popular objects: String, char[], Object[],
ArrayList, HashMap
Heap usage per collecIon: 20.1%
- Unused collecIons
- Small collecIons, 4 or fewer elements (most
significant problem)
- Sparse collecIons, capacity is 2 Imes or more
than what you need](https://image.slidesharecdn.com/javabehindthescenes-161213100342/85/Igor-Dmitriev-Java-behind-the-scenes-12-320.jpg)
![- Node<K,V>[] table[10]
- table.length = 64
- O(n)
- Client(number)](https://image.slidesharecdn.com/javabehindthescenes-161213100342/85/Igor-Dmitriev-Java-behind-the-scenes-19-320.jpg)
![- Node<K,V>[] table[10]
- table.length = 64
- O(logn)
- Client(number)](https://image.slidesharecdn.com/javabehindthescenes-161213100342/85/Igor-Dmitriev-Java-behind-the-scenes-21-320.jpg)
Igor Dmitriev: "Java behind the scenes"
- 7. Empty ArrayList is iniIalized with Object array of size 10: Object[] elementData = new Object[10];
- 10. Delombok
- 11. Nathan Reynolds Is an Architect at and works in PSR(Performance, Scalability and Reliability), team dedicated towards opImizing Oracle Middleware soVware. He is the Exalogic Performance Architect. In this role, he oversees the technical aspects of analyzing profiles, figuring out opImizaIons, opImizing code and measuring performance impact.
- 12. Analysed 670 Java heap dumps from different Java programs to find out memory hogs. Most popular objects: String, char[], Object[], ArrayList, HashMap Heap usage per collecIon: 20.1% - Unused collecIons - Small collecIons, 4 or fewer elements (most significant problem) - Sparse collecIons, capacity is 2 Imes or more than what you need
- 17. jdk 1.8.0_b132 HashMap hash collision
- 19. - Node<K,V>[] table[10] - table.length = 64 - O(n) - Client(number)
- 21. - Node<K,V>[] table[10] - table.length = 64 - O(logn) - Client(number)
- 24. HashMap When?
- 28. ConcurrentHashMap jdk 1.7.0_40 - concurrencyLevel (default 16) - Segment - Retrieval operaIons are non-blocking - Fail-safe iterator - sun.misc.Unsafe is used for concurrency operaIons