JDKのバージョンの切替、確認、インストール（Mac OS X）

最新のJDKのインストール

Homebrew-caskでインストールしていきます。

まずはbrewのupdateから

$ brew update

Homebrew-caskのJDKバージョンを確認

$ brew cask info java

java: 1.8.0_45
Java, Java Standard Edition Development Kit
http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
Not installed
https://github.com/caskroom/homebrew-cask/blob/master/Casks/java.rb
==> Contents
  JDK 8 Update 45.pkg (pkg)
==> Caveats
This Cask makes minor modifications to the JRE to prevent issues with
packaged applications, as discussed here:

  https://bugs.eclipse.org/bugs/show_bug.cgi?id=411361

If your Java application still asks for JRE installation, you might need
to reboot or logout/login.

Installing this Cask means you have AGREED to the Oracle Binary Code
License Agreement for Java SE at

  http://www.oracle.com/technetwork/java/javase/terms/license/index.html

Homebrew-caskでインストール

$ brew cask install java

JDKのバージョンの切替

$ export JAVA_HOME=`/usr/libexec/java_home -v 1.8.0_45`

JDKのバージョンの確認

$ java -version

java version "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, mixed mode)

インストールされているJDKのバージョンを確認

$ /usr/libexec/java_home -V

Matching Java Virtual Machines (4):
    1.8.0_45, x86_64:	"Java SE 8"	/Library/Java/JavaVirtualMachines/jdk1.8.0_45.jdk/Contents/Home
    1.7.0_75, x86_64:	"Java SE 7"	/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home
    1.6.0_65-b14-462, x86_64:	"Java SE 6"	/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home
    1.6.0_65-b14-462, i386:	"Java SE 6"	/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home