Abstract classes and interfaces in Java serve fundamentally different purposes. Learn the differences between these Java language elements and how to use them in your programs.

Learn how to use JAAS and Twilio API to create a custom login module for two-factor authentication in a Java web service.

How does the open-closed SOLID principle work in a Java program? Here we show you what this important principle means, and how to implement the open-closed principle in Java.

Java doesn’t support multiple inheritance through class extension, however. When viewing an inheritance hierarchy, you can easily detect multiple inheritance by the presence of a diamond pattern.