A , commonly known as a JAR file, is a package file format used to aggregate many Java class files and associated metadata and resources (text, images, etc.) into a single file for distribution. Based on the ZIP file format, it allows Java runtimes to efficiently deploy entire applications or libraries as a single unit. The Core Components of a Java Archive
While "JAR" is the most common term, the Java ecosystem uses specialized archive formats for different environments: Archive Type .jar General-purpose libraries or desktop applications. Web Archive (WAR) .war Used for deploying web applications to a servlet container. Enterprise Archive (EAR) .ear java archives
my-app.jar ├── META-INF/ │ ├── MANIFEST.MF (metadata – version, main class, classpath) │ ├── INDEX.LIST (optional – for faster class loading) │ └── *.SF / *.DSA (signature files if signed) ├── com/ │ └── mycompany/ │ └── App.class ├── images/ │ └── logo.png └── config.properties A , commonly known as a JAR file,
| Format | Purpose | |--------|---------| | | Java code + resources (ZIP based) | | WAR | Web applications (servlets/JSP) – extends JAR | | EAR | Enterprise apps (multiple WARs/JARs) | | APK | Android packages (similar structure) | Web Archive (WAR)
: Located at META-INF/MANIFEST.MF , this file contains metadata about the archive, such as the entry point (the "Main-Class") for executable JARs.
: The manifest allows developers to define versioning information and dependencies. Working with JAR Files