https://devops-monk.com/tags/function/Recent content in Function on Devops MonkHugoen-usMon, 04 May 2026 00:00:00 +0000https://devops-monk.com/tutorials/java8/functional-interfaces/Mon, 04 May 2026 00:00:00 +0000https://devops-monk.com/tutorials/java8/functional-interfaces/What Is a Functional Interface? A functional interface is an interface with exactly one abstract method (SAM — Single Abstract Method). This is the type the compiler targets when you write a lambda expression. @FunctionalInterface public interface Comparator<T> { int compare(T o1, T o2); // the single abstract method // default and static methods are allowed } The @FunctionalInterface annotation is optional but highly recommended — it makes the intent explicit and causes the compiler to fail if you accidentally add a second abstract method.