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Java 21 is an LTS release with several features that change how production code is written — not incrementally, but fundamentally. Here is what each feature actually does, where it applies, and what it replaces.
Read moreHashMap is the most-used data structure in Java and one of the least understood internally. The hash function, bucket structure, tree conversion, and resize behavior all have practical consequences for performance and correctness.
Read moreSpring's @Transactional annotation hides significant machinery: proxy creation, connection management, propagation behavior, and rollback rules. The bugs that come from misunderstanding this machinery are among the hardest to diagnose in Spring applications.
Read moreJava performance problems fall into four categories, each with different symptoms, different tools, and different fixes. Misidentifying the category means optimizing the wrong thing. Here is how to tell them apart and what to do about each.
Read moreJPA abstracts SQL but does not eliminate the need to think about it. The fetch strategy, the columns selected, and the SQL generated determine whether your queries are fast or slow at scale. Here is how to control each layer.
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