For example, you might use a vending machine interface to select an item, pay for it, and receive a food or drink item. From a programming perspective, an interface sits between software components.

The functional Predicate interface gets used extensively by the Java 8 Streams API. Any developer who wants to master functional programming in Java will need to be comfortable with the Predicate ...

For example, a Java program obtains file I/O (input/output) services by creating objects from various file-related classes in Java’s class library and calling their methods.

Don't be intimidated by the prospect of doing functional programming in Java. This step-by-step example will help you learn basic Java lambda syntax quickly and effectively.