Java 8 streams are currently a major focus of developer interest. As an alternative to iterative processing, stream code with lambdas has great advantages in conciseness and readability. But how fast is it? In this session we'll use case studies to illustrate the performance advantages—and pitfalls—of streams, both sequential and parallel. The session will place the discussion of stream code performance in the framework of a structured approach to analysing performance problems, one that can be applied to measuring and tuning any Java application.