Context

Teams building services and digital products at Publicis Sapient often process collections of campaign, customer, or event data in Java. Interviewers want to know whether you can use Java 8 Streams to write code that is both readable and production-ready.

Core Question

Explain how Java 8 Streams improve code readability compared with imperative loops. In your answer, cover:

1. How streams express filtering, mapping, grouping, and aggregation more clearly.
2. When streams are a good choice in a production codebase and when a traditional loop is better.
3. Common pitfalls, including debugging difficulty, side effects, overuse of parallelStream(), and performance trade-offs.

Scope Guidance

Answer at the level expected from an engineering leader who still makes sound coding decisions. You should discuss readability, maintainability, correctness, and performance, and use short code examples to compare loop-based and stream-based approaches. You do not need to explain every stream API method, but you should show that you understand practical usage and trade-offs.