If it is Linux, you can try the unzip command:
unzip -l your_jar_file.jar
From Java you can also list the jar file contents. It must be something like this:
ZipFile jarFile = new ZipFile( jarFilePath );
Enumeration<? extends ZipEntry> entries = jarFile.entries();
while( entries.hasMoreElements() ) {
System.out.println( entries.nextElement().getName() );
}