Day 9: Functional interface

Functional interface

A functional interface or single abstract method interface is a special type of interface. It can still declare default methods, and even toString() without breaking the single-abstract-method constraint because the implementation can come from Object at runtime.

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@FunctionalInterface
interface MyFunctionalInterface {
    void init();

    default String addString(String str) {
        return str + str;
    }

    String toString();
}

public class Day09 {
    public static void main(String[] args) throws IOException, InterruptedException {
        MyFunctionalInterface myFunctionalInterface =
            () -> System.out.println("My functional Interface");
        myFunctionalInterface.init();
    }
}

The original LinkedIn graphic is preserved below.