While using a JAR file when a directory is specified in the classpath, the files are searched in the directory specified and not in the directories up in the hierarchy. Also, the dot (.) operator means that the files are to be searched in the current directory also. The list of the files in the Windows environment are separated using a semicolon (;).

In the case of the Unix environment, the names of the files are separated using the colon (:) operator. In the command-line, the directory structure is represented using the forward slash (/) in place of the backward slash (\). The semicolon (;) separated list of directories specify the locations to search the files in the specified directories. The files are searched in the directories specified, and not in the directories up in the hierarchy. For example:

-classpath uc\ProgramCodeFiles\MyFiles;uc\JAVAFiles;.;

Here, files will be searched in the current directory, the MyFiles directory, and the JAVAFiles directory.

A JAR file is a bundling and deploying utility that executes upon Java programs. The JAR tool is used to create a JAR file. The file contains class files, image files, and audio/video files. It also contains a manifest file, which contains information such as whether the class file is a javabean, or which class contains the main method, etc. The basic syntax of the command for creating a JAR file is as follows:

jar -cf jar-file input-file(s)

where,

c indicates a JAR file is going to be created.
f indicates the output of the command execution will go to a file rather than to stdout.
jar-file is the name of the resulting JAR file.
input-file(s) specify a space-separated list of one or more files that are going to be included in the JAR file. It can use the wildcard * symbol.

After using this command, it will generate a compressed JAR file and place it in the current directory. It also generates a default manifest file for the JAR archive.