Parallel streams can help for CPU-bound work on large collections when each element is independent and the work is heavy enough to amortize overhead. Pitfalls: they use `ForkJoinPool.commonPool` by default, they can be slower for small tasks, they are bad for blocking I/O, and side effects/shared mutable state can cause race conditions.
Expanding on the short answer — what usually matters in practice:
A tiny example (an explanation template):
// Example: discuss trade-offs for "parallel-streams:-when-can-they-help-and-what-ar"
function explain() {
// Start from the core idea:
// Parallel streams can help for CPU-bound work on large collections when each element is ind
}