Question

49. Explain how you want to name packages and how you want to divide a program in packages. Suppose you're talking about a new program, you do not need to worry about any previous package structure. (5p) 50. How would you like to package utility classes? Indicate in which package(s) you would place a class that parses strings and a class that handles URLs. (5p

Answer 1

49)

Java packages are always written in lowercase letters. Not like Java classes, where the first letter is usually a capital letter.

To avoid creating packages with the same names as other public Java packages it is recommended that you start your package hierarchy with the reverse domain name of your company. For instance, since the domain name of my company is abcd.com I should start with a package structure called com.abcd . In other words, a top level package named com with a subpackage inside called abcd.

Java packages are a mechanism to group Java classes that are related to each other, into the same "group" (package). When a Java project grows bigger, for instance an app or API, it is useful to split the code into multiple Java classes, and the classes into multiple Java packages. When you divide classes into multiple Java packages, it becomes easier to figure out where a certain class you are looking for is.

A Java package is like a directory in a file system. In fact, on the disk a package is a directory. All Java source and class files of classes belonging to the same package are located in the same directory.

Java packages can contain subpackages. Java packages can thus make up what is called a package structure. A Java package structure is like a directory structure. Its a tree of packages, subpackages and classes inside these classes. A Java package structure is indeed organized as directories on your hard drive, or as directories inside a zip file (JAR files).