Java Parallel Stream | When NOT to Use Parallel Streams | Performance, Pitfalls & Best Practices
In this video, we’ll understand Java Parallel Streams simply and practically.
Instead of jumping straight into code, we’ll first discuss:
Why parallel streams exist
How they work internally
When they improve performance
When they actually make your code slower
We’ll also cover real examples, common mistakes, and best practices that every Java developer should know before using parallel streams in production code.
📌 What you’ll learn:
What is a Parallel Stream in Java
Difference between Sequential Stream and Parallel Stream
How parallel streams use ForkJoinPool internally
When to use parallel streams
When NOT to use parallel streams
Thread-safety issues and side effects
Performance considerations & best practices
This video is ideal for:
✔ Java developers
✔ Java 8+ learners
✔ Interview preparation
✔ Developers curious about performance optimisation
Timestamps:
00:00 What you’ll learn in this video
00:21 What is a parallel stream in Java Streams
00:37 Getting wrong list size | Example 1
02:53 Using synchronized list gives the right result | Example 2
03:55 Common mistakes & best practices
04:14 Summary
📌 Note: Parallel streams are powerful, but using them blindly can cause bugs and performance issues. Understanding the “why” is more important than memorising syntax
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