Stream API, Lambda Expressions & Functional Processing
Filter, map, flatMap, reduce, and collect collection elements declaratively using Java 8+ Streams API and functional interface lambdas.
Stream Pipeline Architecture & Lazy Evaluation
### Stream Processing Stages
1. **Source**: Collection stream (`list.stream()`).
2. **Intermediate Operations**: Lazy transformations returning a stream (`filter()`, `map()`, `sorted()`, `flatMap()`).
3. **Terminal Operation**: Triggers evaluation and returns a result (`collect()`, `reduce()`, `count()`, `findFirst()`).
