What is the difference between interfaces and functional interfaces in Java?

What is the difference between interfaces and functional interfaces in Java?

In Java, an interface is a reference type that can contain constants, method signatures, default methods, static methods, and nested types. A functional interface, on the other hand, is a special type of interface that contains exactly one abstract method, making it suitable for lambda expressions.

Can you give me an example of a functional interface?

Sure! A common example of a functional interface is the Runnable interface, which has a single method run(). You can implement it using a lambda expression like this: Runnable task = () -> System.out.println("Task is running");.

Are there any restrictions on functional interfaces?

Yes, a functional interface can only have one abstract method. However, it can have multiple default or static methods.

Why are functional interfaces important in Java?

Functional interfaces are important because they enable the use of lambda expressions, which provide a clear and concise way to represent a single method interface.