用zsh，修改～/.zshrc
修改这些文件之后，重修打开terminal，配置不会丢
首先确保已经安装了jdk：
## check the present running java
which java ## check java version
java -version
以zsh为例：
## check all the available jdk
/usr/libexec/java_home -V ## check the top jdk
/usr/libexec/java_home ## check some jdk (eg. version 1.7)
/usr/libexec/java_home -v 1.7 ## edit .zshrc to set java_home variable
vim ~/.zshrc ## add the following line into the file
export JAVA_HOME=$(/usr/libexec/java_home) ## you can also use the following line to set the variable, which is not recommended, only for older mac os.
## export JAVA_HOME=/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home ##let the configuration in .zshrc take effect
source ~/.zshrc ## check if configure succeed
echo $JAVA_HOME
如果用bash，修改~/.bash_profile 或 ~/.profile；