Structure your answer by grouping the features into functional programming (lambdas, streams, Optional) and platform improvements (default methods, date/time). For each feature, briefly explain what it is, then give a concrete example of when you'd use it in a real project, emphasizing trade-offs and best practices.
Pro tip: Mention that while Java 8 features like streams and lambdas improve readability, they can introduce performance overhead and debugging challenges; show you understand when to avoid them, such as in tight loops or when side effects are needed.
Start by categorizing Java 8 features into language enhancements (lambdas, default methods) and library additions (Streams, Optional, Date/Time). This shows you understand the broader impact.
Define lambda expressions as concise representations of anonymous functions, and mention functional interfaces like Runnable, Comparator, and the new java.util.function package. Give an example of using a lambda to simplify event handling or sorting.
Explain that streams enable declarative, pipeline-based processing of collections. Highlight common operations (filter, map, reduce) and when to use them—e.g., data transformation, filtering, and aggregation—while noting they are not always faster than loops.
Explain Optional as a container to avoid null checks and express intent, but caution against overuse (e.g., not for fields or parameters). Describe default methods as a way to add methods to interfaces without breaking existing implementations, useful for API evolution.
Introduce java.time (LocalDate, LocalTime, ZonedDateTime, etc.) as immutable and thread-safe, replacing the flawed Date and Calendar. Give an example of when you'd use it, such as handling time zones or date arithmetic.
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