What to do if you have installed Java for OS X on macOS

If you have installed JDK6 on macOS Sierra or OS X El Capitan using Java for OS X, it was quite difficult to remove it cleanly, so make a note.

environment

• macOS Sierra 10.12 -Java for OS X (Delete this)

$ sw_vers
ProductName:	Mac OS X
ProductVersion:	10.12
BuildVersion:	16A323

problem

The question "what's wrong?" Is that you can't change the symbolic links created when you install Java for OS X (ln -fs, ʻunlink, rm`).

The symbolic link in question is below.

$ ls -al /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK
lrwxr-xr-x  1 root  wheel  59  1 27 01:03 /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK ->  /Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents

This doesn't disappear easily. The ln command seems to pass and does not change, and the ʻunlink and rm` commands return Permission denied.

Cause

After investigating, it seems that the cause was that protection by a function called SIP (System Integrity Protecton) implemented after ʻOS X El Capitan` was working.

There were people who were having trouble with the same thing on stackexchange, so it was very helpful. => [delete-unnecessary-files-in-system-library-for-mac-os-x](http://apple.stackexchange.com/questions/214538/delete-unnecessary-files-in-system-library- for-mac-os-x)

Solution

Once you know this, it's not that difficult to deal with later. Follow the steps below.

1. Start restarting your Mac and press and hold ⌘ + r before booting.
2. Make sure the macOS utility starts.
3. From the menu, open Utilities> Terminal.
4. In an open terminal, type csrutil disable to run it. (This command disables SIP.)
5. After confirming the execution, reboot as usual.
6. After rebooting, open the terminal again and ʻunlink` the target symbolic link or delete the linked directory.
7. After deleting, if there is a path of the JDK you want to switch to, make a symbolic link to /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK.

that's all. After all the operations, it is recommended to start macOS utility again and run csrutil enable to enable SIP just in case.

If you want to install JDK6

Let's install it with Homebrew. You can install JDK6 with the following command.

However, even with this method, /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK may be overwritten, so it may be better to prepare for checking the path of the symbolic link and replacing it. not.

$ brew cask install java6

$ ls /Library/Java/JavaVirtualMachines/
1.6.0.jdk/        jdk1.7.0_79.jdk/  jdk1.8.0_121.jdk/ jdk1.8.0_91.jdk/

$ ls -al /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK
8 lrwxr-xr-x  1 root  wheel  59  2  4 20:11 /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK -> /Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents 

$ sudo unlink \
> /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK

$ sudo ln -s \
> /Library/Java/JavaVirtualMachines/jdk1.8.0_121.jdk/Contents \
> /System/Library/Frameworks/JavaVM.framework/Versions/CurrentJDK