linux系统查看java_home安装目录，配置环境变量

1.查看java安装目录

执行命令，逐步寻找java安装目录

[root@localhost bin]# which java
/usr/bin/java
[root@localhost bin]# ls -lrt /usr/bin/java
lrwxrwxrwx. 1 root root 22 Nov 29 16:27 /usr/bin/java -> /etc/alternatives/java
[root@localhost bin]# ls -lrt /etc/alternatives/java
lrwxrwxrwx. 1 root root 71 Nov 29 16:27 /etc/alternatives/java -> /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-1.el7.x86_64/jre/bin/java

2.修改环境变量文件

[root@localhost bin]# vi /etc/profile

在文件中添加：

##JAVA_HOME处为上面找到的目录
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-1.el7.x86_64/jre	
export PATH=$JAVA_HOME/bin:$PATH
export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar

3.使配置生效

source /etc/profile