Managing Java classpath (Windows)

The classpath can connect to the Java runtime and the file system. It defines where the compiler and interpreter should look for the. class file to load. The basic idea is that the hierarchy of the file system reflects the hierarchy of the Java package, while the Classpath defines which directory in the filesystem can be the root of the Java package hierarchy.

Unfortunately, the file system is often very complex and relies on the platform, and it does not match well with Java packages. This is especially true in Windows environments. Java is designed by some Unix masters, and in many ways, this means that it does not synchronize well with Windows conventions. As a result, both new users and senior Java programmers are deeply troubled by the classpath. Yes, it's really not a good side of the Java platform, it lets you get off the clock and still be busy debugging a stubborn little problem.

Of course, using an excellent IDE like Eclipse can reduce some of the difficulties of managing the classpath, but only a few, and the premise must be that everything is normal (but this is unlikely because there will always be some surprises). As a result, every Java programmer must have a thorough understanding of the classpath, only so that the problems that arise in the classpath can be debugged.

In this article, I give you all the information you need to know about the Java classpath (and related source paths) in Windows. The companion chapter of this article shows similar techniques on UNIX and Mac OS X. Follow the steps listed here to prevent unnecessary classpath failures and resolve most of the problems that occur.

Package structure

To master the Classpath, start with the source code. Each class belongs to a package that must adhere to a standard naming convention. Simply put, the name of the package starts with an Upside-down level two domain name, such as Com.example or Edu.poly, followed by at least one or more words to describe the contents of the package. For example, suppose you have a domain name for elharo.com, and if you want to create a fraction class, you can put it in the following package:

Com.elharo.math

Com.elharo.numbers

Com.elharo.math.algebra.fields

After the reversed domain name, you need to use the child package name of the single word. Do not use abbreviated forms, and make sure you are spelling correctly. You can use the spelling checker if you want. Most problems related to classpath are caused by a slightly different spelling or abbreviation used in a word in the source code and in a file system. So the best thing to do is to always use a name that is spelled correctly and has no initials.

The entire package name should be lowercase, even if the name is some idiomatic name and abbreviation that is often taken in uppercase elsewhere. Windows usually does not distinguish between capitalization in file names, but Java and some UNIX file systems. If you need to move files between different systems, the problem of capitalization will certainly cause some trouble.

Package names must all be made up of ASCII characters. Some compilers also accept package names written with Hebrew, Cyrillic, Greek, or other scripts, but most file systems are not accepted; As you'll see later, the package names must assume the dual tasks of being directory names. Java packages and class names are Unicode, but many file systems (including FAT) do not recognize Unicode. Unfortunately, there are so many FAT systems. Simply copying files to the system with a different default encoding will make the compiler and interpreter unable to find the correct class.

Do not attempt to save cost on package names. In the long run, this will only be harmful and not a benefit. If you need a domain name, buy one. If the name is too long buy a shorter one (I once bought xom.nu such a domain name, so my package prefix is only 6 characters). Do not place the class in the default package (the default package is the package that is given by default if a package statement is not included in the class). If package access is not conducive to communication between objects, you need to add more public methods to the class. Classes that need to be used more than once must be placed in a package.

Configure Windows

File extensions and paths are important for both Java and Windows. So before you start the following steps, be sure to see them. Hiding part of the file name is acceptable to end users (but I don't think so), but obviously not for developers. To resolve this issue, you will need to make some changes to some of the default settings for Windows Explorer.

First open any folder on the Windows desktop. Find the Tools menu and choose Folder Options. In the dialog box that opens later, confirm that you have selected the following three options, as shown in Figure 1:

The Display the full path in the address bar should be selected.

"Display the full path in title bar" should be selected.

"Hide file extensions for known file types" should be cleared.

Figure 1. Windows Explorer Options

You may also want to check "Show hidden files and folders", which has little impact on your Java job, but personally I'd like to see everything I'm doing. Selecting these options reveals more details about what you are doing and makes it easier for you to debug the problems that occur.