Developers typically use the jar command-line tool or integrated development environments (IDEs) like Eclipse or IntelliJ IDEA to build archives.
: Bundling files into one archive reduces overall file size, making them easier to store and faster to download over a network.
Since Java 9, a new format called was introduced, and JARs were enhanced to support modules.
Beginners often confuse these.
| Feature | | WAR (Web Application Archive) | | :--- | :--- | :--- | | Purpose | General purpose libraries and applications. | Specifically for Java Web Applications. | | Structure | Standard package structure. | Strict structure (e.g., WEB-INF , web.xml ). | | Execution | Run on the JVM directly or used as a library. | Must be deployed inside a Servlet Container (Tomcat, Jetty). |
Compile and build applications with IntelliJ IDEA - JetBrains
Because they are compressed, you cannot easily view or edit source files inside them without specialized tools like JD-GUI or a standard unzip utility. java archive
To see what is inside a JAR without extracting it fully:
gradle jar
java -Xms512m -Xmx2048m -jar filename.jar Developers typically use the jar command-line tool or
While a JAR holds your classes, it doesn't automatically include the external libraries your code depends on. Developers often have to create "fat JARs" (or "Uber-JARs") to bundle everything together, which can be tricky to configure manually.
What differentiates a JAR from a standard ZIP file is the file. This is a special file inside the archive that contains metadata about the JAR, such as which class contains the main method or what other libraries are required.
<build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-jar-plugin</artifactId> <version>3.3.0</version> </plugin> </plugins> </build> Beginners often confuse these
: JAR files can be digitally signed to verify the author's identity and ensure the code hasn't been tampered with.
This contains your code AND all your dependencies (other JARs) inside a single file. This is preferred for distribution because you don't need to worry about installing libraries separately.