yum安装的JDK的没有配置环境变量但是在/usr/bin下面都做了软链接

[root@st152 /usr/bin]# ll |grep java
lrwxrwxrwx    1 root root         22 Nov 28 22:14 java -> /etc/alternatives/java
lrwxrwxrwx    1 root root         23 Nov 28 22:14 javac -> /etc/alternatives/javac
lrwxrwxrwx    1 root root         25 Nov 28 22:14 javadoc -> /etc/alternatives/javadoc
lrwxrwxrwx    1 root root         23 Nov 28 22:14 javah -> /etc/alternatives/javah
lrwxrwxrwx    1 root root         23 Nov 28 22:14 javap -> /etc/alternatives/javap
[root@st152 /usr/bin]# ll /etc/alternatives/java
lrwxrwxrwx 1 root root 73 Nov 28 22:14 /etc/alternatives/java -> /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.151-1.b12.el7_4.x86_64/jre/bin/java