Stream.map() + Java Generics – Everything You’ve Been Missing! | Stream API | Generics | Java 8

In this comprehensive 2-hour deep dive, we break down everything you didn't know you needed to fully understand the map() method in Java’s Stream API — especially the confusing generics like ? super T and ? extends R.

Whether you're a beginner trying to understand functional programming in Java, or an experienced developer struggling with Java Generics and PECS (Producer Extends, Consumer Super), this tutorial is for you.

⏱️ Timestamps
-------------------------
00:00:00 - Stream.map() + Java Generics Deep Dive – Everything You’re Missing!
00:02:21Practical Examples: Real-World Mapping with Java Streams
00:11:02 - How to Create a Custom map() Clone in Java
00:26:03 - Making map() Method Fully Generic – Step-by-Step
00:36:11 - Understanding `? super T` – map() Function Input Explained
01:08:20 - PECS Principle Applied to Java Stream.map()
01:27:25 - Why map() Doesn't Use `? extends R` as Input
01:38:39 - map() Return Type: What `? extends R` Really Means
01:47:13 - Building a Stream API map() Clone from Scratch

💡 What You’ll Learn
✅ How Java Stream.map() works under the hood
✅ What ? super T and ? extends R really mean
✅ How to apply the PECS principle in real-world code
✅ How to write your own version of the map() method
✅ Why understanding generics is key to mastering streams

#javatutorial #javastreams #javagenerics

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