The Classpath The concept of a path should be familiar to anyone who has worked on a DOS or Unix platform. It’s an environment variable that provides an application with a list of places to look for some resource. The most common example is a path for executable programs.

Setting the Classpath in Java This page is obsolete. To use our standard library files (StdDraw.java, StdIn.java, and StdOut.java), you can place them in the same directory as the main program you are writing. In order to run Java, two things are most important, PATH and CLASSPATH. In order to use Java from the command line, you also need to define JAVA_HOME.

In a Unix shell, the PATH environment variable is a colon-separated list of directories that are searched, in order, when the user types the name of a command. Wd 4tb my passport for mac. The Java CLASSPATH environment variable, similarly, is a list of locations that are searched for Java class files. Both the Java interpreter and the Java compiler use the CLASSPATH when searching for packages and Java classes. An element of the classpath can be a directory or a JAR file. Java also supports archives in the conventional ZIP format, but JAR and ZIP are really the same format.

JARs are simple archives that include extra files (metadata) that describe each archive’s contents. JAR files are created with the JDK’s jar utility; many tools for creating ZIP archives are publicly available and can be used to inspect or create JAR files as well. The archive format enables large groups of classes and their resources to be distributed in a single file; the Java runtime automatically extracts individual class files from the archive as needed. The precise means and format for setting the classpath vary from system to system.

On a Unix system (including Mac OS X), you set the CLASSPATH environment variable with a colon-separated list of directories and class archive files:% export CLASSPATH =/ home / vicky / Java / classes: / home / josh / lib / foo. This example specifies a classpath with three locations: a directory in the user’s home, a JAR file in another user’s directory, and the current directory, which is always specified with a dot (.). The last component of the classpath, the current directory, is useful when you are tinkering with classes. On a Windows system, the CLASSPATH environment variable is set with a semicolon-separated list of directories and class archive files: C: > set CLASSPATH = C: home vicky Java classes; C: home josh lib foo. The Java launcher and the other command-line tools know how to find the core classes, which are the classes included in every Java installation. Mac c times font download. The classes in the java.lang, java.io, java.net, and javax.swing packages, for example, are all core classes so you do not need to include these classes in your classpath.

The classpath may also include “*” wildcards that match all JAR files within a directory. For example: export CLASSPATH =/ home / pat / libs /* To find other classes, the Java interpreter searches the elements of the classpath in order. The search combines the path location and the components of the fully qualified class name. For example, consider a search for the class animals.birds.BigBird. Searching the classpath directory /usr/lib/java means the interpreter looks for an individual class file at /usr/lib/java/animals/birds/BigBird.class.

Searching a ZIP or JAR archive on the classpath, say /home/vicky/myutils.jar, means that the interpreter looks for component file animals/birds/BigBird.class within that archive. For the Java runtime, java, and the Java compiler, javac, the classpath can also be specified with the -classpath option:% javac - classpath / home / pat / classes: / utils / utils. Java If you don’t specify the CLASSPATH environment variable or command-line option, the classpath defaults to the current directory (.); this means that the files in your current directory are normally available. If you change the classpath and don’t include the current directory, these files will no longer be accessible.