- Arrays
The structure everything else is built on: a fixed-length block of memory where index arithmetic makes any element reachable in one step. What that buys you, what it costs on insert and delete, and why the fixed length is the whole problem.
- Spring Boot – JPA and Hibernate
Entities, relationships and the persistence context. Lazy loading and the N+1 query it hands you, why open-in-view is switched off here, soft deletes with @SQLRestriction, and the ddl-auto setting to use once something other than Hibernate owns your schema.
- Python – Conditional Statements
if, elif and else, what Python considers falsy and why that surprises people, the conditional expression, chained comparisons, and when `match` is genuinely clearer than a chain of elifs.
- Optional
Optional is a container that either holds a value or is empty. Its purpose is not to eliminate null — it is to move "there might be nothing here" out of your head and into the type signature, where the compiler and the next reader can both see it. The problem it solves Nothing forces a caller of…
- Collectors class
A stream pipeline has to end somewhere. collect is the general-purpose ending, and the Collectors class supplies the recipes — turn this stream into a list, a map, a grouped report, or one joined string. There are dozens of them and you do not need dozens. Six do almost all the work in practice,…