Linux 查找Java 的安装路径

find /usr/ -name *jdk

上面的命令会找到不少个路径的话，你须要用以下这个命令查找具体的jdk路径。

$ java -showversion -verbose 2>&1 | head -1


[Opened /usr/lib/jvm/java-1.7.0-openjdk-1.7.0.75.x86_64/jre/lib/rt.jar]

另外参考博文

~/.bash_profile is a startup script which generally runs once. This particular file is used for commands which run when the normal user logs in. Common uses for .bash_profile are to set environment variables such as PATH, JAVA_HOME, to create aliases for shell commands, and to set the default permissions for newly created files.

Set JAVA_HOME / PATH for a single user/仅仅设置单个登陆用户有效

Login to your account and open .bash_profile file
$ vi ~/.bash_profile
Set JAVA_HOME as follows using syntax export JAVA_HOME=<path-to-java>. If your path is set to /usr/java/jdk1.5.0_07/bin/java, set it as follows:
export JAVA_HOME=/usr/java/jdk1.5.0_07/bin/java
Set PATH as follows:
export PATH=$PATH:/usr/java/jdk1.5.0_07/bin
Feel free to replace /usr/java/jdk1.5.0_07 as per your setup. Save and close the file. Just logout and login back to see new changes. Alternatively, type the following command to activate the new path settings immediately:
$ source ~/.bash_profile
OR
$ . ~/.bash_profile
Verify new settings:
$ echo $JAVA_HOME
$ echo $PATH
Tip: Use the following command to find out exact path to which java executable under UNIX / Linux:
$ which java

Please note that the file ~/.bashrc is similar, with the exception that ~/.bash_profile runs only for Bash login shells and .bashrc runs for every new Bash shell.

Set JAVA_HOME / PATH for all user/设置多个用户有效

You need to setup global config in /etc/profile OR /etc/bash.bashrc file for all users:
# vi /etc/profile
Next setup PATH / JAVA_PATH variables as follows:
export PATH=$PATH:/usr/java/jdk1.5.0_07/bin
export PATH=$PATH:/usr/java/jdk1.5.0_07/bin

Save and close the file. Once again you need to type the following command to activate the path settings immediately:
# source /etc/profile
OR
# . /etc/profile