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.

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.