The Java(TM) programming language is a modern, evolutionary computing language that combines an elegant language design with powerful features that were previously available primarily in specialty languages. In addition to the core language components, Java programming language software distributions include many powerful, supporting software libraries for tasks such as database, network, and graphical user interface (GUI) programming. In this panel, we focus on the core Java language features.

The Java programming language is a true object-oriented (OO) programming language. The main implication of this statement is that in order to write programs, you must work within its object-oriented structure.

Object-oriented languages provide a framework for designing programs that represent real-world entities such as cars, employees, insurance policies, and so on. Representing real-world entities with nonobject-oriented languages is difficult because it's necessary to describe entities such as a truck with rather primitive language constructs such as Pascal's record, C's struct, and others that represent data only.

The behavior of an entity must be handled separately with language constructs such as procedures and/or functions, hence, the term procedural programming languages. Given this separation, the programmer must manually associate a data structure with the appropriate procedures that operate on, that is, manipulate, the data.

In contrast, object-oriented languages provide a more powerful class construct for representing user-defined entities. The class construct supports the creation of user-defined data types, such as Employee, that represent both the data that describes a particular employee and the manipulation or use of that data.

Java programs employ user-defined data types liberally. Designing nontrivial Java classes requires, of course, a good working knowledge of Java syntax. The following panels illustrate Java syntax and program design in the context of several Java class definitions.