删除/usr/bin/java即可
terwer@terwer-PC:~$ sudo rm /usr/bin/java
[sudo] terwer 的密码：
terwer@terwer-PC:~$ java -version
Picked up _JAVA_OPTIONS: -Dawt.useSystemAAFontSettings=gasp
java version "1.8.0_191"
Java(TM) SE Runtime Environment (build 1.8.0_191-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.191-b12, mixed mode)
terwer@terwer-PC:~$