具体的请参考这两篇文章： https://blog.csdn.net/dragonassassin/article/details/51010947 https://blog.csdn.net/liangrui1988/article/details/50684117
jdk的 查找 whereis java echo $JAVA_HOME https://www.cnblogs.com/imyalost/p/8745137.html
ls -lrt /usr/bin/java
lrwxrwxrwx 1 root root 22 Apr 3 19:30 /usr/bin/java -> /etc/alternatives/java
ls -lrt /etc/alternatives/java
