获取java安装路径前要判断是否已经安装成功java
执行命令：
java
Usage: java [-options] class [args...]
(to execute a class)
or java [-options] -jar jarfile [args...]
(to execute a jar file)
where options include:
-d32 use a 32-bit data model if available
-d64 use a 64-bit data model if available
-server to select the "server" VM
The default VM is server.
-cp <class search path of directories and zip/jar files>
-classpath <class search path of directories and zip/jar files>
A : separated list of directories, JAR archives,
and ZIP archives to search for class files.
-D<name>=<value>
.......
在查看java版本：
java -version
[root@localhost Desktop]# java -version
openjdk version "1.8.0_65"
OpenJDK Runtime Environment (build 1.8.0_65-b17)
OpenJDK 64-Bit Server VM (build 25.65-b01, mixed mode)
----------------------------------分割线--------------------------------------
如果以上2步都没问题就可以查询安装路径了
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如果在/etc/profile文件中配置了JAVA_HOME则可以直接获取：
echo $JAVA_HOME
[root@localhost local]# echo $JAVA_HOME
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.65-3.b17.el7.x86_64/jre/bin/java
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如果以上方法无法查询到，使用如下：
[root@localhost local]# which java
/usr/bin/java
[root@localhost local]# ls -lrt /usr/bin/java
lrwxrwxrwx. 1 root root 22 Mar 7 19:12 /usr/bin/java -> /etc/alternatives/java
[root@localhost local]# ls -lrt /etc/alternatives/java
lrwxrwxrwx. 1 root root 70 Mar 7 19:12 /etc/alternatives/java -> /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.65-3.b17.el7.x86_64/jre/bin/java
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然后编辑/etc/profile文件,在文件末尾添加
vi /etc/profile
export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.65-3.b17.el7.x86_64/jre/bin/java
export PATH=
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JAVA_HOME/bin:
JAVAHOME/bin:PATH
export CLASSPATH=.:
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JAVA_HOME/lib/dt.jar:
JAVAHOME/lib/dt.jar:JAVA_HOME/lib/tools.jar
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保存命令设置
source /etc/profile
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在执行查看命令：
[root@localhost local]# echo $JAVA_HOME
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.65-3.b17.el7.x86_64/jre/bin/java
