$ which java
/usr/bin/java
$ readlink -f $(which java)
/usr/lib/jvm/jdk1.7.0_79/bin/java
$ update-java-alternatives -l
java-1.7.0-openjdk-amd64 1071 /usr/lib/jvm/java-1.7.0-openjdk-amd64
$ alternatives --display java
java - status is auto.
link currently points to /usr/java/jdk1.6.0_25/bin/java
/usr/java/jdk1.6.0_25/bin/java - priority 1000
Current `best' version is /usr/java/jdk1.6.0_25/bin/java.
$ find /usr -name java
/usr/share/bash-completion/completions/java
find: `/usr/share/doc/google-chrome-stable': Permission denied
/usr/share/java
/usr/lib/jvm/jre1.6.0_45/bin/java
/usr/lib/jvm/jdk1.7.0_79/jre/bin/java
/usr/lib/jvm/jdk1.7.0_79/bin/java
/usr/lib/jvm/jdk1.6.0_45/db/demo/programs/scores/java
/usr/lib/jvm/jdk1.6.0_45/db/demo/programs/vtis/java
/usr/lib/jvm/jdk1.6.0_45/jre/bin/java
/usr/lib/jvm/jdk1.6.0_45/bin/java
/usr/lib/jvm/jdk1.8.0_91/jre/bin/java
/usr/lib/jvm/jdk1.8.0_91/bin/java
/usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java
/usr/lib/jvm/java-7-openjdk-amd64/bin/java
/usr/lib/libreoffice/share/Scripts/java
/usr/bin/java