ubuntu 下安装JDK

wget -c http://download.oracle.com/otn-pub/java/jdk/8u45-b14/jdk-8u45-linux-x64.tar.gz

sudo mkdir /usr/lib/jvm
sudo tar zxvf jdk-8u45-linux-x64.tar.gz -C /usr/lib/jvm 

sudo gedit /etc/profile

#set java environment
export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_45  
export JRE_HOME=${JAVA_HOME}/jre  
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib  
export PATH=${JAVA_HOME}/bin:$PATH 

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.8.0_45/bin/java 300
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.8.0_45/bin/javac 300

sudo update-alternatives --config java

java -version