intermediateFunctional Programming
What are UnaryOperator and BinaryOperator, and how do they differ from Function and BiFunction?
UnaryOperator<T> is a specialization of Function<T, T> where the input and output types are the same — used for operations like String::toUpperCase that transform a value into the same type. BinaryOperator<T> is a specialization of BiFunction<T, T, T> for combining two values of the same type into one, which is exactly the shape Stream.reduce() expects (e.g. Integer::sum).
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