官網下載：
http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
tar xzvf 文件名創建安裝路徑：
mkdir /usr/llib/jvm
mv /home/lem/下載/jdk1.8.0_20/usr/llib/jvm
vi /etc/profile
export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_20
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH