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How to Declare a Class - Java

Well it's been a while since we discussed Java and I graced these pages with its complicated beauty (for an example of complicated beauty, take a peek at Hillary Swank, who is pretty in a well...complicated sort of way). In this new series of articles, we will be discussing Classes.

  1. Java Classes
  2. How to Declare a Class
  3. Using Public Methods to Obtain Private Fields
  4. Naming Conventions for Our Pal, the Method
  5. Creating Objects with Constructors
By: James Payne
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January 09, 2008

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There are several ways to define your classes. The simplest would be:

class YourClass {

declare your field, constructor, and methods here


You can also define them in a more complex manner: 

class YourClass extends YourSuperClass implements SomeInterface {

declare your field, constructor, and methods here


Here is a list of components class declarations can contain:

  • Public, Private, and other modifiers.

  • Class Name.

  • Superclass name, if applicable with the keyword extends before it.

  • The keyword implements followed by a list of interfaces (separated by commas).

  • Body of the class, encapsulated with braces{}.

Variables in Classes

We discussed variables and data types in a previous article, but they need a little further discussion here, as they relate to classes.

Variables in classes are known as member variables and are called fields. They are composed of a modifier (such as public or private), a type, and a name. An example would be:

public int myEnormousIQ;

In the above example, the public portion of our declaration is known as an access modifier. It determines which classes have access to the member field. There are several access modifiers: public, protected, package, and private.

  • Public: can be referenced from anywhere in the application by the class in which it is defined.

  • Package: can be referenced by only the same package through the class in which it was defined.

  • Private: can only be referenced by the class in which it was defined.

  • Protected: can be referenced by its class and subclass and from its package.

>>> More Java & J2EE Articles          >>> More By James Payne

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