Also called a SAM (Single Abstract Method). An FI is an interface containing :
- One and only one abstract method;
- Zero or many static methods
- Zero or many default methods
There are many built-in functional interfaces included in Java 8. The Predicate FI is one of them.
Here is an example of a functional interface :
@FunctionalInterface interface MostBasicFi{ boolean test(); // a static method public static void foo1(){ // add some logic... } // a default method public static void foo2(){ // add some logic... } }