Guava Release 10 introduces the Optional class, which can be used where one might use a null object . I have built my own classes like this before, but the advantage of Guava's providing it is ...

This is optional but it contributes to readable code, especially if anyone else is going to be working on it. ... This is because classes in Java are absolutely fundamental to the way it works.

java.lang: A collection of language-related classes, such as Object and String, organized in the java package’s lang subpackage; java.lang.ref: A collection of reference-related language classes ...

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 ...