parallel data processing and performance

Parallel streams allow Java to divide data-processing work across multiple threads so that operations can potentially run faster on multi-core processors. However, parallel processing does not automatically improve performance and can sometimes make an application slower. In this section, you’ll learn how parallel streams work, how Java uses the Fork/Join framework, and when parallel processing is useful. You’ll also understand the impact of data size, operation cost, shared state, and thread overhead. The goal is to help you decide when parallel processing is appropriate and when a normal sequential stream is the better choice.