To build a lambda function, you don't need to create a functional interface. You can use the interface to generate instances for future function calls.
Lambda expressions take advantage of multi-core systems' parallel processing capabilities, as shown in the Stream API's capability for pipeline operations on data. They are anonymous methods (methods without names) that are used to implement a functional interface method.
More Efficiency When doing bulk operations on collections, we can obtain higher efficiency (parallel processing) by leveraging the Stream API and lambda expressions. Additionally, lambda expressions aid in collection internal iteration rather than external iteration.