You can run Java apps in two ways. The first is to run Java applets inside your Web browser with a plug-in. The second is to run native Java apps on your Mac. With the grave security concerns about Java these days, you may be thinking about how to remove or disable both of those Java systems completely from your Mac. This how-to discusses procedures to uninstall/disable both the plug-in ahd the full Java system. It also looks at the differences between Java 6 and Java 7.
1. Java Applets & Plug-ins
Many Mac users retain the ability to run Java applets in their browser with abrowser plug-in. Oracle now maintains that plug-in for Mac users. If you, because of recent security alerts, upgraded that plug-in to Java 1.7 (or "Java 7" in Java-speak) from Oracle, you'll find the plug-in in /Library/Internet Plug-ins. The file is "JavaAppletPlugin.plugin" and has the icon shown on the left.
Also, when you installed Oracle's Java 7 browser plug-in, you installed a Preference Pane in System Preferences under "Other."
Fig 1. Oracle's Java Preference Pane
That Preference Pane manages the Oracle Java 7 browser plug-in for applets. It will auto-detect that a new version is available, but it will not do the installation. You need to do that yourself under the Update tab.
Fig 2. The Update Tab. Available updates will be presented.
Java 7 won't run in Chrome because Chrome is 32-bit and Java 7 is 64-bit. That leaves Safari and Firefox as the remaining major Mac browsers.
Disabling the Browser Plug-in
The best way to block the applet plug-in in /Library/Internet Plug-ins for both Safari and Firefox browsers is to disable it in the Java Preference Pane. Uncheck the box circled below and restart your browser.
Fig 3. Disable Java for browsers.
By the way, you can verify which version is installed by looking at the Java tab and select "View..."
Fig 4. Verify the plug-in version.
You can also dig down into the plug-in with the terminal app and extract the version number.
> /Library/Internet\ Plug-Ins/JavaAppletPlugin.plugin/Contents/Home/bin/java -version
I showed this command not to be geeky but to reveal the structure of Oracle's Java applet plug-in. You can do that your self by using "Show Package Contents" on the plug-in.
Alternatively, to be really safe, you could delete the file: "JavaAppletPlugin.plugin" in /Library/Internet Plug-ins. But that would make it harder to easily re-enable the plug-in if you ever need it.
Most of the security issues reported so far relate to this Java applet plug-in for browsers because it is the vehicle through which maliciously crafted websites work.
Apple stopped providing its own Java browser plug-in in October, 2012 and a subsequent Software Update deleted it. Oracle has assumed responsibility for the Java applet plug-in since then.
Finally, you can test whether your Java plug-in has been disabled by going to Oracle's Java applet test page: http://www,java.com/en/download/testjava.jsp . (Safari and Firefox may respond slightly differently.) Only if your plug-in is up to date, enabled and working properly, will you see this:
Java browser plug-in up to date and working properly.
2. Java Applications and Java 6
Depending on the history of your Mac, you may still have Java 1.6 (or "Java 6" in Java-speak) installed for both development and native Java applications. Java 6 is a full-fledged development system that allows developers to write and you run full Java applications such as CrashPlan or jEdit. Apple, not Oracle, still maintains Java 6 for OS X based on patches provided by Oracle. (However, Oracle seems ready to stop issuing those updates for non-corporate users.)
The Two Different Java Systems
This is what confuses many users. They know they upgraded the applet plug-in for the browser, but the terminal command "java -version" doesn't refer to the plug-in. It shows you the version of Apple's full Java 6 package for development and native apps. They may have different version numbers.
Snow Leopard
Up through OS X 10.6, Snow Leopard*, Apple provided Java 6 pre-installed, and they still maintain it. The latest version is 1.6.0_43. If you've kept your system up to date with Apple Software updates, and you open a terminal window and type "java -version" (without the quotes), you should see this:
Fig 5. Getting the Java 6 version number.
I'll get to how to disable that Java install further down.
Lion & Mountain Lion
If you bought a new Mac with Lion or Mountain Lion pre-installed, Java 6 is not there. It's an optional install nowadays.
If you upgraded a Snow Leopard Mac to Lion and/or Mountain Lion, I believe that the install process suppressed Java 6 without a complete uninstall. From looking at my two Macs, it appears that the upgrade removed the directory/folder: /System/Library/Java/JavaVirtualMachines. That will stop any Java application cold in is tracks from running.
On such a Mac, if you enter "java -version" you'll get a prompt inviting you to install Java 6, like this:
Fig 6. Invitation to install Java 6
Or perhaps you installed Java 6 in order to run an older version of GoToMeeting. Or an Adobe installer may have done it.
After a Java 6 installation, there is a large collection of Java files is deeply embedded into OS X, and, unlike the simple plug-in for the browser, it's not easy to uninstall all those files. And no formal uninstaller exists. Matthew Dornquast of Code42 Software told me that the only SAFE way to remove all vestiges of Java 6 is to conduct a clean install of 10.8. And from then on, say "no" if ever asked to install Java.
Is Java 6 Installed?
To see if Java 6 is installed, on the command line, enter, after the prompt:
> java -version
If you see the invitation to install Java 6, shown in Fig. 6, you don't have an operational Java system for applications. (Recommended response: "Not now.") If you see a result like I showed in Fig 5, then it should be Java 1.6.0_43 (as of this writing.)
Uninstalling Java 6
Various websites and forum commenters have suggested a few tricky ways, from the command line, to partially uninstall Java 6 by deleting certain directories or files. There are several serious problems with deleting specific Java 6 files:
- Java 6 isn't really, completely uninstalled.
- Some applications or suites, for example from Adobe, depend on Java being on the Mac in that form. If you munge about, deleting key Java files, all kinds of unexplainable things might happen down the road.
- It's hard to re-enable Java for full applications if you need it unless you have very accurate notes on those files you deleted (or renamed). Believe me.
- Some of those examples use the diabolically dangerous "rm -rf" shell command, which if misunderstood and mistyped or misused, could damage your Mac and require you to reinstall OS X.
The best advice I have is to keep your Java 6 up to date and secure using the OS X Software Update function. After a period of inattention, Apple is being much more aggressive in keeping Java 6 up to date and secure. At some point in the future, you'll buy a new Mac with OS X 10.8 or 10.9 installed, and your Mac will be 100 percent free of Java 6. For now, if you're concerned about native Java apps that access websites, just don't run them.
Note that on a Mac without Java 6, you could still install Oracle's browser plug-in as described above.
3. Java Applications and Java 7 JDK
If you, because of security alerts, somewhere along the line, installed Oracle's Java 7 Development Kit (JDK), then entering the command "java -version" will reflect that Oracle's Java 7 has been installed for development. However, Apple's Java 6 is not deleted, (they can co-exist) and as I wrote here, "What Mac Users Need to Know About the Java Security Update":
More importantly, unless you know what you're doing with Java development, [installing Java 7 JDK] could break any stand-alone Java 6 apps you may have been using that depend on knowing where to find Java 6. (Most Java apps for the Mac have been written in Java 6). The bottom line: don't install the (Java 7) JDK from Oracle unless you're an expert user."
Summary
It is very difficult to simply disable and re-enable Java 6, let alone delete it entirely, without Unix experience. Expert users may elect to delete key files to prevent Java 6 apps from ever running, but it's not a great idea for the average user without Unix and command line experience. It's better to be aware if you're running a native Java app, built for Java 6, and then keep Java 6 updated (with Software Update in OS X). Otherwise, find an alternative non-Java solution.
Remember, you're not vulnerable if you run a native Java 6 app, say, a text editor like jEdit, that doesn't visit websites like a browser plug-in is designed to do.
If you really, really want to completely eradicate Java 6 from your Mac, which isn't really necessary, you'll need to do a clean install of Lion or Mountain Lion.
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* There are security issues with Java 6 on 10.5 Leopard that will never be fixed.