Nếu tập tin không tồn tại, bạn chỉ đơn giản là có thể sử dụng in, println, và lệnh printf như bạn đã làm khi in Ý: Bạn có thể xây dựng một máy quét với một tham số chuỗi, nhưng máy quét diễn giải các chuỗi như là dữ liệu, không phải là một tên tập tin. | Chapter 4. Objects and Classes Simpo PDF Merge and Split Unregistered Version - http 153 Packages needs cleaning. Just as importantly if a class you use has such a method you need to call it when you are done with the object. Packages Java allows you to group classes in a collection called a package. Packages are convenient for organizing your work and for separating your work from code libraries provided by others. The standard Java library is distributed over a number of packages including and so on. The standard Java packages are examples of hierarchical packages. Just as you have nested subdirectories on your hard disk you can organize packages by using levels of nesting. All standard Java packages are inside the java and javax package hierarchies. The main reason for using packages is to guarantee the uniqueness of class names. Suppose two programmers come up with the bright idea of supplying an Employee class. As long as both of them place their class into different packages there is no conflict. In fact to absolutely guarantee a unique package name Sun recommends that you use your company s Internet domain name which is known to be unique written in reverse. You then use subpackages for different projects. For example is a domain that one of the authors registered. Written in reverse order it turns into the package . That package can then be further subdivided into subpackages such as . From the point of view of the compiler there is absolutely no relationship between nested packages. For example the packages and have nothing to do with each other. Each is its own independent collection of classes. Class Importation A class can use all classes from its own package and all public classes from other packages. You can access the public classes in another package in two ways. The first is simply to add the full package name in front of every .
