linux comes with java looking java_home
[zzh@hadoop ~]$ which java
/usr/bin/java
[zzh@hadoop ~]$ echo $JAVA_HOME
[zzh@hadoop ~]$ ls /usr/bin/java
/usr/bin/java
[zzh@hadoop ~]$ ls -l /usr/bin/java
lrwxrwxrwx. 1 root root 22 12月 3 18:05 /usr/bin/java -> /etc/alternatives/java #软链接
[zzh@hadoop ~]$ ls -l /etc/alternatives/java
lrwxrwxrwx. 1 root root 71 12月 3 18:05 /etc/alternatives/java -> /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-7.b13.el7.x86_64/jre/bin/java #软链接
[zzh@hadoop ~]$ cd /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-7.b13.el7.x86_64/jre/bin/java
bash: cd: /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-7.b13.el7.x86_64/jre/bin/java: 不是目录
[zzh@hadoop ~]$ cd /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.181-7.b13.el7.x86_64/jre/
[zzh@hadoop jre]$ ls
bin lib
[zzh@hadoop jre]$
