Metaclasses allow you to deeply modify the behaviour of Python classes (in terms of how they're defined, instantiated, accessed, and more) by replacing the
type metaclass that new classes use by default.
Oracle official style guide for the Java Programming Language is a standard followed by developers at Oracle and recommended to be followed by any other Java developer. It covers filenames, file organization, indentation, comments, declarations, statements, white space, naming conventions, programming practices and includes a code example.
In order to use custom tags in JSP,we used to have TLD files,along with a Java class to define the custom tags but post JSP 2.0 specs,the same can be achieved,without the need for any Source code files,making it easy to maintain and it can also be created by someone with basic knowledge of JSP tags without need for java code.
You can use hierarchical queries to retrieve data based on a natural hierarchical relationship between rows in a table
Creating a class in Pharo is as simple as sending
subclass: message to another class object. But most of the classes are created and modified in a system browser (currently Nautilus).