直接下JDK，里面包含Jre
http://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html
原装openjdk在
/usr/lib/jvm
Uncompress archive
Now you uncompress and move the whole uncompressed folder to /opt (optional) directory.
tar -xzvf /root/jdk-7u79-linux-x64.tar.gz mv jdk1.7.0_79 /opt cd /opt/jdk1.7.0_79
Install and register binaries
This step registers the downloaded version of Java as an alternative, and switches it to be used as the default:
update-alternatives --install /usr/bin/java java /opt/jdk1.7.0_79/bin/java 1 update-alternatives --install /usr/bin/javac javac /opt/jdk1.7.0_79/bin/javac 1 update-alternatives --install /usr/lib/mozilla/plugins/libjavaplugin.so mozilla-javaplugin.so /opt/jdk1.7.0_79/jre/lib/amd64/libnpjp2.so 1 update-alternatives --set java /opt/jdk1.7.0_79/bin/java update-alternatives --set javac /opt/jdk1.7.0_79/bin/javac update-alternatives --set mozilla-javaplugin.so /opt/jdk1.7.0_79/jre/lib/amd64/libnpjp2.so
Testing your installation
First of all, close your browser and re-open. You won’t believe how many users actually forgets to do this step and later complains Java ain’t working. I’d advise to bookmark this site to be able to reopen these instructions quickly, or simply copy these into a leafpad / vi / text-editor.
To check the version of Java you are now running
java -version
To check the browser plugin just click Do I have Java?
This should take you to Oracles Java website and you will see a confirmation message.