🚀 Java Functional Programming with Lambda & Streams

This repository demonstrates Java Functional Programming concepts using Lambda Expressions, Streams API, and Method References with concise, real-world examples.

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📌 What is Functional Programming?

Functional Programming focuses on writing declarative, immutable, and side-effect-free code using functions as first-class citizens.

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🔹 Lambda Expressions ✨

• Lambda Expression – A concise way to implement functional interfaces using anonymous functions.
• Syntax – (parameters) -> expression or (parameters) -> { statements }.
• Functional Interface – An interface with exactly one abstract method.

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🔹 Built-in Functional Interfaces 🧩

• Predicate – Takes one input and returns a boolean.
• Function – Takes one input and returns a result.
• Consumer – Takes one input and performs an action without returning a result.
• Supplier – Takes no input and returns a value.
• BiPredicate – Takes two inputs and returns a boolean.
• BiFunction – Takes two inputs and returns a result.
• BiConsumer – Takes two inputs and performs an action without returning anything.

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🔹 Streams API 🌊

Streams enable functional-style processing of collections using a pipeline of operations.

⚙️ Intermediate Operations

• filter() – Selects elements that match a condition.
• map() – Transforms each element into another form.
• flatMap() – Flattens nested structures into a single stream.
• distinct() – Removes duplicate elements.
• sorted() – Sorts elements in natural or custom order.
• limit() – Restricts the number of elements in a stream.
• skip() – Skips the specified number of elements.

🏁 Terminal Operations

• forEach() – Performs an action for each element.
• collect() – Converts the stream into a collection or final result.
• reduce() – Combines elements into a single value.
• count() – Returns the number of elements.
• anyMatch() – Checks if any element matches a condition.
• allMatch() – Checks if all elements match a condition.
• noneMatch() – Checks if no elements match a condition.
• findFirst() – Returns the first element of the stream.
• findAny() – Returns any element from the stream.

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🔹 Method References 🔗

• Static Method Reference – Refers to a static method using ClassName::methodName.
• Instance Method Reference – Refers to an instance method using object::methodName.
• Constructor Reference – Refers to a constructor using ClassName::new.

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🔹 Optional Class 🛡️

• Optional – A container object used to avoid NullPointerException.
• isPresent() – Checks if a value exists.
• orElse() – Returns a default value if empty.
• orElseGet() – Returns a value from a Supplier if empty.
• orElseThrow() – Throws an exception if the value is absent.

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🎯 Key Benefits 🚀

• Cleaner and more readable code
• Less boilerplate and fewer bugs
• Easy parallel processing with streams
• Improved maintainability and scalability

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👨‍💻 Author

Suvam Debnath