deep dives

the interview-grade internals. source-level, bit-level, no hand-waving.

1. 01HashMap, line by linehash spreading, (n-1) & hash, the resize split, and treeification.
2. 02ConcurrentHashMap internalsCAS on empty bins, locked bin heads, and cooperative resizing.
3. 03the string poolliterals, intern(), and every == trap in one place.
4. 04string concatenation internalsfrom StringBuilder to invokedynamic and StringConcatFactory.
5. 05the integer cachewhy -128..127, and how to make it bigger.
6. 06singletons and double-checked lockingthe half-constructed object, and the three ways to do it right.
7. 07ThreadLocal internalsweak keys, the per-thread map, and the thread pool leak.
8. 08ThreadPoolExecutor internalsthe ctl field: run state and worker count in one int.
9. 09how lambdas are compiledno anonymous classes. invokedynamic and LambdaMetafactory.
10. 10virtual threads, insidecontinuations, mounting, unmounting, and pinning.
11. 11ArrayList vs LinkedList, measuredbig-O says one thing, the CPU cache says another.
12. 12the OutOfMemoryError zooevery OOM message, what it means, and what to do.
13. 13equals and hashCode trapsmutable keys, inheritance, and the object that vanished from a set.
14. 14class loader leakshow redeploying an app leaks an entire copy of it.