Linux
$ update-java-alternatives --list
java-1.11.0-openjdk-amd64 1111 /usr/lib/jvm/java-1.11.0-openjdk-amd64
java-1.8.0-openjdk-amd64 1081 /usr/lib/jvm/java-1.8.0-openjdk-amd64
$ sudo update-java-alternatives --set /usr/lib/jvm/java-1.8.0-openjdk-amd64
update-alternatives: error: no alternatives for mozilla-javaplugin.so
update-java-alternatives: plugin alternative does not exist: /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/amd64/IcedTeaPlugin.so
macOS
$ /usr/libexec/java_home -V
Matching Java Virtual Machines (3):
11.0.9, x86_64: "OpenJDK 11.0.9" /Library/Java/JavaVirtualMachines/jdk-11.0.9+11/Contents/Home
1.8.0_282, x86_64: "Zulu 8.52.0.23" /Library/Java/JavaVirtualMachines/zulu-8.jdk/Contents/Home
1.8.0_221, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_221.jdk/Contents/Home
/Library/Java/JavaVirtualMachines/jdk-11.0.9+11/Contents/Home
export JAVA_HOME=$(/usr/libexec/java_home -v 1.8.0_282)
# or
export JAVA_HOME=$(/usr/libexec/java_home -v 1.8)
jenv
jenvを使っている場合はmacOSの↑の手順が動かない。rbenvっぽく使う。
IntelliJ IDEA
- File > Project Structure > Project Settings > Project > Project SDK
を変更する。