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SeeDev.java for updated tutorials taking advantage of the latest releases.
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Declaring Classes

You've seen classes defined in the following way:

classMyClass {    // field, constructor, and     // method declarations}

This is aclass declaration. Theclass body (the area between the braces) contains all the code that provides for the life cycle of the objects created from the class: constructors for initializing new objects, declarations for the fields that provide the state of the class and its objects, and methods to implement the behavior of the class and its objects.

The preceding class declaration is a minimal one. It contains only those components of a class declaration that are required. You can provide more information about the class, such as the name of its superclass, whether it implements any interfaces, and so on, at the start of the class declaration. For example,

classMyClass extends MySuperClass implements YourInterface {    // field, constructor, and    // method declarations}

means thatMyClass is a subclass ofMySuperClass and that it implements theYourInterface interface.

You can also add modifiers likepublic orprivate at the very beginning—so you can see that the opening line of a class declaration can become quite complicated. The modifierspublic andprivate, which determine what other classes can accessMyClass, are discussed later in this lesson. The lesson on interfaces and inheritance will explain how and why you would use theextends andimplements keywords in a class declaration. For the moment you do not need to worry about these extra complications.

In general, class declarations can include these components, in order:

1. Modifiers such aspublic,private, and a number of others that you will encounter later. (However, note that theprivate modifier can only be applied toNested Classes.)
2. The class name, with the initial letter capitalized by convention.
3. The name of the class's parent (superclass), if any, preceded by the keywordextends. A class can onlyextend (subclass) one parent.
4. A comma-separated list of interfaces implemented by the class, if any, preceded by the keywordimplements. A class canimplement more than one interface.
5. The class body, surrounded by braces, {}.