ubuntu安装jdk

1. 1. Download the following file:
   http://download.oracle.com/otn-pub/java/jdk/7/jdk-7-linux-i586.tar.gz (32-bit)
   http://download.oracle.com/otn-pub/java/jdk/7u1-b08/jdk-7u1-linux-x64.tar.gz (64-bit)
   
   2. Decompress the .tar.gz file.
   
   3. Move the JDK files to /usr/lib/jvm/jdk1.7.0 or elsewhere you like.
   
   4. $sudo gvim /etc/environment  
   
   You will see
   
   PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games"
   
   Change the file as (change the installation path if needed)
   
   PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/lib/jvm/jdk1.7.0/bin"  
   CLASSPATH=.:/usr/lib/jvm/jdk1.7.0/lib  
   JAVA_HOME=/usr/lib/jvm/jdk1.7.0  
   
   And then reload .bashrc file:
   
   source ~/.bashrc
   
   
   5. Run the following commands: 
   
   $sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0/bin/java 300
   $sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0/bin/javac 300
   $sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk1.7.0/bin/javap 300
   $sudo update-alternatives --install /usr/bin/javadoc javadoc /usr/lib/jvm/jdk1.7.0/bin/javadoc 300
   
   Installation has now done. Run $java -version for a test.