Bash profile function to switch JDK versions for Mac users

This is a Bash profile function called switchjdk for Mac users to switch JDK versions on the command line. The switchjdk function changes java, javac and other JDK command for the terminal/shell, and subprocesses. It does not have an effect on things outside that particular terminal.

Rationale

I found myself dissatisfied with both the built-in usr/libexec/java_home capability, as well as jenv even though that otherwise is highly refined. Principally this is because they do not do the right thing for Maven's ~/.maven_rc file at the same time as switching the JDK.

Installation

1. Copy switchjdk-module.bash to /usr/local/etc/
2. Paste the contents of switchjdk-module.bash into ~/.bash_profile
3. Run source ~/.bash_profile

Alternate Homebrew Install

See here

Using switchjdk

$ switchjdk 7
JDK 1.7: JAVA_HOME and PATH changed for this terminal (and subprocesses).

1. This only works on installed JDKs.
2. You can do with JDK numbers (1.4 thru 1.9), or Java numbers (5 thru 9) - Oracle and Apple JDKs. Note 9 is presently 'early access'.
3. You can also do 1.7 thru 1.8 (7 thru 8) for the Zulu varient of the OpenJDK.
4. The script chooses the highest minor version of the JDK to use (say JDK 1.5.1 over 1.5.0). At the time of writing 9 is early access only, and I don't know what the numbers will look like for the real release until closer to that moment.
5. There's a --quiet or -q argument that stops it doing the final line. Example below.
6. Regardless of whether you have Maven installed or not, switchjdk modifies the tiny ~/.maven_rc file appropriately.
7. The switchjdk function does not know about other OpenJDK varients of the JDK (Pull Requests accepted), just the Oracle and Apple and Zulu ones.

The switchjdk command attempts to verify the outcomes, and fast fail if things are not right. E.g. switchjdk 5 on a new Mac will tell you that JDK 1.5 is really a symlink to JDK 6:

$ switchjdk 5
Requested JDK is not really installed. It is symlinked to JDK 1.6

Options

--quiet

$ switchjdk --quiet 7

zulu

$ switchjdk zulu 7
Zulu 1.7: JAVA_HOME and PATH changed for this terminal (and subprocesses).

LICENSE

Copyright (c) 2015 - 2016 Paul Hammant

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Contribtions

Contributions welcome!