第6章 包、接口和异常1（The sixth chapter, package, interface and exception 1）.docVIP

第6章 包、接口和异常1（The sixth chapter, package, interface and exception 1） Main task Describes the use of Java packages (package), interfaces (Interface) and exception handling (exception). 6 and 1. packs Java requires that the file name be the same as the class name. When you put multiple classes together, make sure that the class name is not repeated. When the class is declared a lot, the class name is likely to conflict, which requires a mechanism to manage the class name, which is the package. A package is a mechanism provided by Java that distinguishes class names from space. It is the organization of a class, a package that corresponds to a folder, and packages that contain packages, called packet levels. As in folders, you can have subfolders. In a source, you can declare the package in which the class is located, just as the file is saved to indicate which folder the file is in. The class name in the same package cannot be duplicated, and the same class name can be used in different packages. When the class in the source does not declare the class where the class is located, Java puts the class in the default package, which runs the compilers current folder. At this point, duplicate class names cannot appear. 6.1.1 Java system package Java provides a large number of classes that are divided into different packages for ease of administration and use. Packages are also known as class libraries or API packages, called API (Application Program Interface), which are application interfaces. API package - provides a wealth of classes and methods for you to use, picturesque graphics, playing sound, etc., on the other hand is responsible for dealing with the system software and hardware, the user program functions fully realized. All Java API packages start with java. to distinguish the packages created by the user. 1.java.lang package The java.lang package contains the following main classes: The data type wrapper class corresponds to 8 basic data types, and the data type