Скачать или смотреть How to Open a Java JAR File in Windows

Do you need to open a JAR file? It's easy. Java JAR files are just zip files with a silly .jar extension. Just rename the .jar extension to .zip, and Windows will extract the contents of the JAR file right to your local file system. That's the easiest way to open a JAR. In fact, you don't even need to change the extension. Just open the JAR in WinZip, 7-Zip, WinZip or any other unzip decompression tool.

Now, if when you say 'open a JAR file' you really mean 'run a JAR file' then that's easily achieved as well. Just run the following command:

java -jar jarfilename.jar

Assuming there's a main class defined in the manifest, the JAR file will run right away.

And that's how easy it is to run and open Jar files in Java!