Java 8 Functional Interfaces and Method References Quiz

Functional Interfaces and Method References in Java 8

• A functional interface in Java 8 is an interface with exactly one abstract method that matches the parameter and return types of a lambda expression.
• The java.util.function package contains general purpose functional interfaces that can be used by end users.
• An interface annotated with @FunctionalInterface is not required for the Java compiler to determine the interface as functional, but it helps to identify accidental violations of design intent.
• Rules for @FunctionalInterface include having exactly one abstract method, allowing any number of default methods, and allowing the interface to override a public method.
• The Predicate<T> interface in java.util.function has a boolean-valued function that takes an argument and returns a boolean value.
• Predicate<T> can be used to identify odd numbers from a given set or find specific employees from a list of employees.
• Predicate<T> has default methods for logical AND, logical OR, and logical negation.
• Java 8 introduces primitive functional interfaces, which deal with only three primitive types: int, long, and double.
• Primitive functional interfaces avoid the extra cost associated with boxing and unboxing of generic types.
• Method references provide an efficient way to build lambda expressions that call existing methods.
• There are three types of method references: reference to static method, reference to an instance method of a particular object, and reference to an instance method of an arbitrary object of a particular type.
• Method references can also be used for constructors, with the syntax being the same as for static methods.