1. Remove all Java related packages (Sun, Oracle, OpenJDK, IcedTea plugins, GIJ):
(1) apt-get update
(2) apt-cache search java | awk '{print($1)}' | grep -E -e '^(ia32-)?(sun|oracle)-java' -e '^openjdk-' -e '^icedtea' -e '^(default|gcj)-j(re|dk)' -e '^gcj-(.*)-j(re|dk)' -e 'java-common' | xargs sudo apt-get -y remove
(3) apt-get -y autoremove
2. Clear configuration information: dpkg -l | grep ^rc | awk '{print($2)}' | xargs sudo apt-get -y purge
3. Clear java configuration and cache: bash -c 'ls -d /home/*/.java' | xargs sudo rm -rf
4. Manually clear JVMs: rm -rf /usr/lib/jvm/*
https://blog.csdn.net/swuteresa/article/details/13335481