linux經過命令安裝jdk，查看文件目錄

查看安裝目錄

which java
/usr/bin/java
ls -lrt /usr/bin/java
lrwxrwxrwx. 1 root root 22 Dec 17 15:12 /usr/bin/java -> /etc/alternatives/java
ls -lrt /etc/alternatives/java
lrwxrwxrwx. 1 root root 46 Dec 17 15:12 /etc/alternatives/java -> /usr/lib/jvm/jre-1.8.0-openjdk.x86_64/bin/java
cd /usr/lib/jvm

配置環境變量

export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk.x86_64
export CLASSPATH=.:$JAVA_HOME/jre/lib/rt.jar:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar 
export PATH=$PATH:$JAVA_HOME/bin

使環境變量生效

使環境變量生效
source /etc/profile