ubuntu 安装JDK7

1.下载JDK

http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html

2.解压

sudo tar zxvf jdk-7u45-linux-x64.tar.gz

3.

sudo mkdir /usr/java;
sudo chmod -R 777 java;
sudo cp -r  jdk1.7.0_45  /usr/java/

4.设置环境变量

sudo vim ~/.bashrc

"
export JAVA_HOME=/usr/java/jdk1.7.0_45
export JRE_HOME=${JAVA_HOME}/jre  
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib  
export PATH=${JAVA_HOME}/bin:$PATH
"
source ~/.bashrc

5.设置默认的JDK版本

sudo update-alternatives --install /usr/bin/java java /usr/java/jdk1.7.0_45/bin/java 300  
sudo update-alternatives --install /usr/bin/javac javac /usr/java/jdk1.7.0_45/bin/javac 300  
sudo update-alternatives --install /usr/bin/jar jar /usr/java/jdk1.7.0_45/bin/jar 300

6.查看JAVA_HOME

sudo update-alternatives --config java 

7.查看java版本

java -version