#05 | Built-in Functional Interfaces (MUST) | Predicate, Function, Consumer and Supplier | Java 8

Описание: Java 8 Built-in Functional Interfaces – Complete Explanation

In this video, I explain the four most important built-in functional interfaces in Java 8 that are must-know for interviews.

These interfaces are heavily used in Streams, Lambda expressions, and real-world Java applications.

🔹 1️⃣ Predicate Interface
Used to test a condition
Takes one input
Always returns boolean (true or false)
Commonly used in filtering logic

🔹 2️⃣ Function Interface
Takes an input and returns an output
Used for transformation logic
Very common in Stream API operations

🔹 3️⃣ Consumer Interface
Takes an input but returns nothing
Mainly used for printing, logging, or consuming data
Often used with forEach()

🔹 4️⃣ Supplier Interface
Takes no input
Always returns an output
Used for generating values like random numbers or default objects

🔹 Why These Interfaces Are Important
They reduce boilerplate code
They are the foundation of Java 8 functional programming
Almost every Java 8 interview expects knowledge of these interfaces

🔹 Key Takeaways
Predicate → test condition
Function → input to output
Consumer → input only
Supplier → output only

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