Lambda Functions #
A lambda function is a quick and easy unnamed function defined by some variables. They often take the syntax (var1, var2) -> {do something here}.
Functional Interface #
A functional interface is an interface that consists of one single abstract method (SAM). The goal here is to ensure that every class implementing the interface has that specific capability, such as shorting or doing something in a multithreaded context. Unfortunately, this can lead to an awful lot of classes, which is why we often also use anonymous classes and lambda functions instead of functional interfaces.
Java Streams #
A Stream is like an actual stream – it spits stuff out and you take it as it comes. You can pass a stream into a bunch of functions like filter(), which takes a predicate (criterion) and, well, filters everything in the Stream; sorted(), to sort stuff using lambda functions; map(), which returns the output of another function for each stream item; limit(), which only takes the first n elements from the stream; distinct(), which removes duplicates; and collect(), which gathers all the items togetner into some collection.
Predicate is used in filter(), Comparator is used in sorted(), Consumer is used in foreach, and Function is used in map().