官網下載jdk7
http://www.oracle.com/technetwork/java/javase/downloads/java-archive-downloads-javase7-521261.html
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創建安裝目錄
sudo mkdir /usr/local/java
解壓至/usr/local/java
sudo tar -zxvf jdk-7u80-linux-x64.tar.gz -C /usr/local/java/
增加環境變量，修改/etc/profile,在最后增加
#set java env
export JAVA_HOME=/usr/local/java/jdk1.7.0_80
export CLASSPATH=.:$JAVA_HOME/lib
export PATH=$JAVA_HOME/bin:$PATH
環境變量立即生效
source /etc/profile
測試
Java -version
