Java’s single inheritance limitation is usually not a problem in the normal course of development. In fact, the need to use multiple inheritance could be a sign of a bad design.

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.

Sealed classes make Java an even more powerful and expressive language and set the stage for even more sophisticated techniques such as pattern matching, which we'll explore in a subsequent article. A ...