If the app is written in Java, then it would use .jar files.
I'm guessing that you have a particular app in question...
Maybe if you tell the name of the app, someone may know (or it will be apparent from the app itself)
OR, maybe you can contact the developer, ask them!
Just curious - What will you gain by discovering what language was used by the developer?
Over the weekend, I was accessing a document online to print it. The website wouldn't allow direct access but would allow me to print if I used their system. I clicked to go ahead and an alert popped up telling me my installed Java was too old, and inviting me to proceed to Oracle to get the latest. The post installation instructions told me to restart all apps that use Java. Hence my question.
The app I was using was Safari. Since I have to restart that frequently anyway , that particular issue is resolved.
That's it (?)
Safari is not a Java app, but would use the Java plugin that you make available.
The situation would depend on the web site, and not your browser at all. In other words, your installed version of Java is too old, and would be reported the same way regardless of the browser that you use - when you try to access and use features that use java.
Current version of Java is Java 8 Update 31.
If that is your only need for Java, you can go to Safari preferences/Security, then Internet Plugins, Website settings.
That page will list ALL of your available plugins, and give you the choice to configure individual sites for each plugin.
That list will show the version that you have installed.
I would likely select your site from the list there, and choose the Allow the java plugin - assuming it is a site that you want to trust for that - and block when visiting all other websites. The settings are right there.
Then, you could perhaps get that latest version of Java and install that. It would then only affect that one site that you choose.
Java download here: http://www.oracle.com/technetwork/java/javase/downloads/index.html
(JRE download only, unless you need one of the other downloads - you would know if that's the case)
Recheck the security settings after you have updated Java to make sure that only that site is allowed.
And - you're set!