What is parallel streams in Java?

Parallel streams in Java are a feature introduced in Java 8 that allow developers to process collections of data in parallel, utilizing multiple threads to improve performance for large data sets. They are part of the Stream API, which enables functional-style operations on collections. With parallel streams, tasks can be split into smaller parts and executed concurrently, making it easier to leverage multi-core processors.

By using parallel streams, you can take advantage of the underlying hardware capabilities without manually managing threads, allowing for concise and high-level code. However, it is important to consider the context of usage as parallel processing can introduce overhead and may not always yield performance benefits for smaller collections.