Summary of Creating Classes - Java Tutorial 5.0 英文版

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Summary of Creating Classes

A class definition has two parts: a class declaration and a class body. For details about the elements of a class declaration, refer to the table in the Declaring Classes section. The class body contains member variables, methods, and constructors for the class. A class uses member variables to contain state and uses methods to implement behavior. The table in Declaring Member Variables lists the possible elements of a member variable declaration and the table in the Defining Methods section lists the possible elements of a method declaration. Constructors initialize a new instance of a class and look like methods with the same name as the class but without a return type.

You control access to member variables and methods in the same way: by using an access specifier, such as private or public, in the member's declaration. The table in Controlling Access to Members of a Class section lists the access specifiers and the effect of each specifier.

You specify a class member variable or a class method by using the static keyword in the member's declaration. A member that is not declared as static is implicitly an instance member. Class variables are shared by all instances of a class and can be accessed through the class name. Instances of a class get their own copy of each instance variable, which must be accessed through an instance reference.

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