Просмотр установленных версий Java на Ubuntu.

see-all-java-version.sh

$ file `which java javac`
# /usr/bin/java:  symbolic link to /etc/alternatives/java
# /usr/bin/javac: symbolic link to /etc/alternatives/javac

$ file /etc/alternatives/java /etc/alternatives/javac
# /etc/alternatives/java:  symbolic link to /usr/lib/jvm/java-11-openjdk-amd64/bin/java
# /etc/alternatives/javac: symbolic link to /usr/lib/jvm/java-11-openjdk-amd64/bin/javac

$ LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8 LANGUAGE=en_US.UTF-8 ls -la /usr/lib/jvm
# total 24
# drwxr-xr-x   4 root root 4096 Sep 13 11:00 .
# drwxr-xr-x 150 root root 4096 Oct 28 20:41 ..
# lrwxrwxrwx   1 root root   25 Apr  8  2018 default-java -> java-1.11.0-openjdk-amd64
# lrwxrwxrwx   1 root root   21 Apr 21  2018 java-1.11.0-openjdk-amd64 -> java-11-openjdk-amd64
# -rw-r--r--   1 root root 2619 Aug 24 23:36 .java-1.11.0-openjdk-amd64.jinfo
# drwxr-xr-x   9 root root 4096 Sep 13 11:00 java-11-openjdk-amd64
# lrwxrwxrwx   1 root root   20 Apr 26  2018 java-1.8.0-openjdk-amd64 -> java-8-openjdk-amd64
# -rw-r--r--   1 root root 2600 Jul 24 01:14 .java-1.8.0-openjdk-amd64.jinfo
# drwxr-xr-x   7 root root 4096 Aug 17 08:22 java-8-openjdk-amd64

$ update-alternatives --list java
# /usr/lib/jvm/java-11-openjdk-amd64/bin/java
# /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java

$ update-java-alternatives -l
# java-1.11.0-openjdk-amd64      1101       /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

$ LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8 LANGUAGE=en_US.UTF-8 sudo update-alternatives --config java
# There are 2 choices for the alternative java (providing /usr/bin/java).
# 
#   Selection    Path                                            Priority   Status
# ------------------------------------------------------------
# * 0            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1101      auto mode
#   1            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1101      manual mode
#   2            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode
# 
# Press <enter> to keep the current choice[*], or type selection number:

# linux - Что означает auto mode в update-alternatives --config java? - Stack Overflow на русском
# https://ru.stackoverflow.com/questions/551304/%D0%A7%D1%82%D0%BE-%D0%BE%D0%B7%D0%BD%D0%B0%D1%87%D0%B0%D0%B5%D1%82-auto-mode-%D0%B2-update-alternatives-config-java

$ LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8 LANGUAGE=en_US.UTF-8 sudo update-alternatives --display java
# java - auto mode
#   link best version is /usr/lib/jvm/java-11-openjdk-amd64/bin/java
#   link currently points to /usr/lib/jvm/java-11-openjdk-amd64/bin/java
#   link java is /usr/bin/java
#   slave java.1.gz is /usr/share/man/man1/java.1.gz
# /usr/lib/jvm/java-11-openjdk-amd64/bin/java - priority 1101
#   slave java.1.gz: /usr/lib/jvm/java-11-openjdk-amd64/man/man1/java.1.gz
# /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java - priority 1081
#   slave java.1.gz: /usr/lib/jvm/java-8-openjdk-amd64/jre/man/man1/java.1.gz

$ /usr/lib/jvm/java-11-openjdk-amd64/bin/java --version
# openjdk 10.0.2 2018-07-17
# OpenJDK Runtime Environment (build 10.0.2+13-Ubuntu-1ubuntu0.18.04.2)
# OpenJDK 64-Bit Server VM (build 10.0.2+13-Ubuntu-1ubuntu0.18.04.2, mixed mode)
$ /usr/lib/jvm/java-11-openjdk-amd64/bin/javac --version
# javac 10.0.2

$ /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java -version
# openjdk version "1.8.0_181"
# OpenJDK Runtime Environment (build 1.8.0_181-8u181-b13-0ubuntu0.18.04.1-b13)
# OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode)
$ /usr/lib/jvm/java-8-openjdk-amd64/bin/javac -version
# javac 1.8.0_181

$ LC_ALL=en_US.UTF-8 LANG=en_US.UTF-8 LANGUAGE=en_US.UTF-8 ls -la /usr/lib/jvm/java-8-openjdk-amd64/bin/java*
# lrwxrwxrwx 1 root root   15 Jul 24 01:14 /usr/lib/jvm/java-8-openjdk-amd64/bin/java -> ../jre/bin/java
# -rwxr-xr-x 1 root root 6312 Jul 24 01:14 /usr/lib/jvm/java-8-openjdk-amd64/bin/javac
# -rwxr-xr-x 1 root root 6312 Jul 24 01:14 /usr/lib/jvm/java-8-openjdk-amd64/bin/javadoc
# -rwxr-xr-x 1 root root 6312 Jul 24 01:14 /usr/lib/jvm/java-8-openjdk-amd64/bin/javah
# -rwxr-xr-x 1 root root 6312 Jul 24 01:14 /usr/lib/jvm/java-8-openjdk-amd64/bin/javap
# -rwxr-xr-x 1 root root 2806 Jul 24 01:14 /usr/lib/jvm/java-8-openjdk-amd64/bin/java-rmi.cgi