Java程序设计TR-Java-lecture05-class.pptVIP

Java程序设计 Java Programming Spring, 2009 Chapter 4: Classes Objects Class Declaration 类的声明 Class Modifiers 类的修饰符 Class Members 类的成员 Class Fields 类的域 Object Creation 类的对象的创建 Fields’ Initilazation 类的域的初始化 Methods 类的方法 Package 包 Class Declaration (类的声明) The class is the fundamental programming unit of the Java programming language. Classes provide the structure for objects and the mechanisms to manufacture objects from a class definition. Each object is an instance of a class. A program is defined by using one or more classes. Class Declaration （类的声明） Example: Class Declaration（类的声明） Syntax(语法): class is a keyword for class declaration. When the compiler sees the word class, it understands that the word after class is the name for the class; The first letter of the name for the class must be a Unicode letter or underline ‘_’ . Class Modifier (类的修饰符) Modifiers are reserved words to specify the properties of the data, methods, and classes and how they can be used. Class modifier: public — a public class is publicly accessible. Without this modifier a class is only accessible within its own package. abstract — used to declare an abstract class. final — a final class cannot be subclassed. strictfp — Strict floating point , a strictfp class has all floating-point arithmetic, defined within the class, evaluated strictly. Class Modifier (类的修饰符) A class declaration can be modified by several modifiers, and modifiers are allowed in any order. A class cannot be both final and abstract!(Why?) Class Members (类的成员) Fields （域） the data variables associated with a class and its objects, which hold the state of the class or object; Methods （方法） contains the executable code of a class and define the behavior of objects. Nested classes nested interfaces （嵌套类和嵌套接口） classes or interfaces declared within the declaration of another class or interface. Fields (域) Syntax: ; = ; Field Types (域的类型) 域可以被声明为基本数据类型和类数据类型 基本数据类型包括： 布尔类型 boolean 字符类型 char 整数类型 b