Functional programming is about promoting functions to first-class citizens in a computer language. This means apart from primitives and objects, reference-typed fields can also directly point to functions, and function arguments can be functions themselves. In addition, a language may also allow for special functional constructs like unnamed lambda calculus functions.
Consider, for example, the following code, which takes a list of strings and adds a “*” to all strings to create a new list:
List<String> l ...
