Archiving Classes with Jar
The jar utility is included with the JDK, and is used to package groups of classes into a bundle. Using the jar tool, you can create, update, extract, list, and index a JAR file. In this phrase, all the classes contained in the current directory from which the jar command is run will be put into a JAR file with the name project.jar. The c option tells the jar utility to create a new archive file. The f option is always followed by a filename specifying the name of the JAR file to use. Complete applications can be distributed as JAR files. Applications can also be executed out of a JAR file without having to first extract them. See the phrase "Running a Program from a JAR File" contained in this chapter for more information about doing this. All classes contained in a JAR file can be easily included on the CLASSPATH when running or compiling a Java application or library. To include the contents of a JAR file in the CLASSPATH, you simply include the path to the JAR file instead of a directory. For example, your CLASSPATH statement might be similar to the following: CLASSPATH=.;c:\projects\fisher.jar;c:\projects\classes This would include all the classes contained in the archive fisher.jar in your CLASSPATH. It is important to note that to include the classes in a JAR file, you must specify the name of the JAR file in the classpath. You cannot just point to a directory containing multiple JAR files as you can for .class files. For more detailed information about using the jar tool, refer to the official JAR documentation from Sun available at: http://java.sun.com/j2se/1.5.0/docs/guide/jar/index.html. |
