Java IO.pdf - Nguyen Dang Binh

Java I/O
example, under Unix, to make the classes in the JAR archive jce12-rc1-dom.jar in the
directory /usr/local/java/lib available to your program, you'd use this command:
% setenv CLASSPATH $CLASSPATH:/usr/local/java/lib/jce12-rc1-dom.jar
The JAR file is treated like a directory in the context of the class path. This is sensible,
because although the archive is a file to the file system, it behaves like a directory to Java.
9.5.1 Meta-Infomation: Manifest Files and Signatures
Aside from the three-letter extension, the only distinction between a zip file and a JAR file is
that most (though not all) JAR files contain a manifest file that lists the contents of the JAR
file as well as various information about those contents. The manifest file is named
MANIFEST.MF and is stored in the META-INF directory at the top of the archive. This file
provides meta-information about the contents of the archive in a particular format. This
directory and file are not necessarily present in the unarchived collection. Generally, a
manifest is added as part of the archiving process. The lefthand side of Figure 9.3 shows a
directory structure for the com.macfaq package that can be stored in a JAR archive. The
righthand side shows the contents of the corresponding JAR archive.
Figure 9.3. JAR archive: before and after
At a minimum, a manifest file must contain this opening line:
Manifest-Version: 1.0
A manifest usually contains additional entries for some of the files in the archive. However,
the manifest does not necessarily contain an entry for every file in the archive. Entries are
separated from each other by a blank line. Each entry is composed of a list of name/value
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