How are exceptions handled in Streams?

• Unchecked exceptions thrown in a lambda propagate out of the terminal operation and abort the pipeline.
• Checked exceptions cannot be thrown from Function, Predicate, and similar types because their functional methods declare no throws clause.
• [Opinion] Options: wrap in a helper that catches and rethrows as unchecked (UncheckedIOException for IOException); map failures into a result type (for example Optional or an Either-style record) and filter later; or move the throwing code out of the stream into a loop when per-element error handling is the core logic.
• In parallel streams an exception from one task is rethrown in the caller; other tasks may continue briefly. [Opinion / Impl — not specified in detail by the Javadoc]
• Streams on I/O resources (Files.lines) must be closed: use try-with-resources; BaseStream is AutoCloseable.

Readability tip: [Opinion] Prefer streams for declarative transforms and aggregations; prefer loops for complex control flow, early exits with multiple states, checked exceptions, or hot paths where profiling shows overhead.

Sources:

• JLS §11 Exceptions
• Function.apply
• UncheckedIOException
• BaseStream.close
• Files.lines