JAR files are packaged with the ZIP file format, so you can use them for “ZIP-like” tasks such as lossless data compression, archiving, decompression, and archive unpacking. These are among the most common uses of JAR files, and you can realize many JAR file benefits using only these basic features.
Even if you want to take advantage of advanced functionality provided by the JAR file format such as electronic signing, you’ll first need to become familiar with the fundamental operations.
To perform basic tasks with JAR files, you use the JavaTM Archive Tool provided as part of the Java Development Kit. Because the Java Archive tool is invoked by using the jar command, for convenience we’ll call it the “Jar tool”.
As a synopsis and preview of some of the topics to be covered in this lesson, the following table summarizes common JAR-file operations:
OperationÂ Â Â Command
To create a JAR fileÂ Â Â jar cf jar-file input-file(s)
To view the contents of a JAR fileÂ Â Â jar tf jar-file
To extract the contents of a JAR fileÂ Â Â jar xf jar-file
To extract specific files from a JAR fileÂ Â Â jar xf jar-file archived-file(s)
To run an application packaged as a JAR file (requires the Main-class manifest header)Â Â Â
java -jar app.jar
To invoke an applet packaged as a JAR fileÂ Â Â