安裝Java7 JDK在Ubuntu上

There is a similar question on how to install JRE 7.

Install the JDK

• Download he 32bit or 64bit Linux "compressed binary file" - it has a ".tar.gz" file extension i.e. "[java-version]-i586.tar.gz" for 32bit and "[java-version]-x64.tar.gz" for 64bit
• Uncompress it
  tar -xvf jdk-7u2-linux-i586.tar.gz (32bit)
  tar -xvf jdk-7u2-linux-x64.tar.gz (64bit)

JDK 7 package is extracted into ./jdk.1.7.0_02 directory. N.B. check carefully this folder name since Oracle seem to change this occasionally with each update.

• Now move the JDK 7 directory to /usr/lib

sudo mkdir -p /usr/lib/jvm
sudo mv ./jdk.1.7.0_02 /usr/lib/jvm/jdk1.7.0

• Now run

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.7.0/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.7.0/bin/javac" 1
sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk1.7.0/bin/javaws" 1

• This will assign Oracle JDK a priority of 1, which means that installing other JDKs will replace it as the default. Be sure to use a higher priority if you want Oracle JDK to remain the default.
• Correct the file ownership and the permissions of the executables:

sudo chmod a+x /usr/bin/java 
sudo chmod a+x /usr/bin/javac 
sudo chmod a+x /usr/bin/javaws
sudo chown -R root:root /usr/lib/jvm/jdk1.7.0

N.B. remember - Java JDK has many more executables that you can similarly install as above. java, javac, javaws are probably the most frequently required.
This answer lists the other executables available.

• Run

sudo update-alternatives --config java

You will see output similar one below - choose the number of jdk1.7.0 - for example 3 in this list:

$sudo update-alternatives --config java
There are 3 choices for the alternative java (providing /usr/bin/java).

Selection Path Priority Status
————————————————————
* 0 /usr/lib/jvm/java-6-openjdk/jre/bin/java 1061 auto mode
1 /usr/lib/jvm/java-6-openjdk/jre/bin/java 1061 manual mode
2 /usr/lib/jvm/java-6-sun/jre/bin/java 63 manual mode
3 /usr/lib/jvm/jdk1.7.0/jre/bin/java 3 manual mode

Press enter to keep the current choice[*], or type selection number: 3
update-alternatives: using /usr/lib/jvm/jdk1.7.0/jre/bin/java to provide /usr/bin/java (java) in manual mode.

Check the version of you new JDK 7 installation:
java -version

java version “1.7.0”
Java(TM) SE Runtime Environment (build 1.7.0-b147)
Java HotSpot(TM) Client VM (build 21.0-b17, mixed mode) 

Repeat the above for:

sudo update-alternatives --config javac
sudo update-alternatives --config javaws

參考自： http://askubuntu.com/questions/55848/how-do-i-install-oracle-java-jdk-7