ASA Programming Guide
Introduction to Java in the Database
A Java seminar
If you are more familiar with procedural languages such as C, or the SQL stored procedure language, than object-oriented languages, this section explains some of the key similarities and differences between procedural and object-oriented languages.
The main structural unit of code in Java is a class.
A Java class could be looked at as just a collection of procedures and variables that have been grouped together because they all relate to a specific, identifiable category.
However the manner in which a class gets used sets object-oriented languages apart from procedural languages. When an application written in a procedural language is executed, it is typically loaded into memory once and takes the user down a pre-defined course of execution.
In object-oriented languages such as Java, a class is used like a template: a definition of potential program execution. Multiple copies of the class can be created and loaded dynamically, as needed, with each instance of the class capable of containing its own data, values, and course of execution. Each loaded class could be acted on or executed independently of any other class loaded into memory.
A class that is loaded into memory for execution is said to have been instantiated. An instantiated class is called an object: it is an application derived from the class that is prepared to hold unique values or have its methods executed in a manner independent of other class instances.