Functional Interface in Java 8

An interface which includes an abstract method, default method , static method and can also override Object class methods.

public interface FunctionalInterface {

     // Only abstract method.

     void abc(Collection collection);

     // Functional interface can have more than one static or default methods.

     default void print() {

           System.out.println("This is default in Functional  Interface.");

     }

    

     //An interface can also have static helper methods from Java 8 onwards.

     static void abc() {

           System.out.println("Hey");

     }

     // And also can override methods of java.lang.Object

     @Override

     public String toString();

}