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 ...

The object passed to addActionListener() is instantiated from an anonymous class that implements the java.awt.event.ActionListener interface. Nested interfaces and 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 ...

Java currently supports only two types of value: primitives and object references. Project Valhalla extends this by introducing inline classes which are a new form of type that exhibit some ...

However, to use any classes in packages other than java.lang in your code, an import is required. The Scanner class is found in the java.util package, not java.lang. Since the Scanner class is found ...