Install JDK7 on CentOS

Install JDK7 on centOs

This tutorial shows you how to install jdk7 on 32bit centOs, 64-bit system is similar.

1. check your java version, enter the following command:
>java -version
It shows something like this:

# java -version
java version "1.6.0_17"
OpenJDK Runtime Environment (IcedTea6 1.7.5)  (rhel-1.31.b17.el6_0-i386)
OpenJDK Client VM (build 14.0-b16, mixed mode)

2. Download JDK7 from oracle's official website(JDK7).
3. Change to root user.(Only root user can install software on Linux)..
>su
enter your root password, and run the JDK file.
>rpm -ivh /home/username/Desktop/jdk-7-linux-i586.rpm
It looks like this:
Preparing...               ################################### [100%]
 1:jdk                        ################################### [100%]
　Unpacking JAR files...
　rt.jar...
　jsse.jar...
　charsets.jar...
　tools.jar...
　localedata.jar...　
4. Setup the environmental variables. We need to find out the "profile" file :
> cd ~
> vim /etc/profile
add the following lines at the bottom of the profile file:

export JAVA_HOME=/usr/java/jdk1.7.0

export CLASSPATH=.:$JAVA_HOME/jre/lib/rt.jar:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar

export PATH=$PATH:$JAVA_HOME/bin

Save your changes and quit:

>:wq

restart your terminal or enter the following command to activate your changes:

> source /etc/profile

5. choose JDK version 

If you use "java -version" to check the JDK version, it is still JDK6, we need to choose JDK7 which we just installed on centOs by "alternative" command

First, we need to install alternative :

> update-alternatives --install /usr/bin/java java /usr/java/jdk1.7.0/bin/java 60
then setup JDK：
> update-alternatives --config java

then it will show the following choises:

-----------------------------------------------
*+ 1           /usr/lib/jvm/jre-1.6.0-openjdk/bin/java
  2              /usr/lib/jvm/jre-1.5.0-gcj/bin/java
  3              /usr/java/jdk1.7.0/bin/java
Press Enter to save your current choise, or enter number:3. Now we are almost done.
6. Verify your java version
> 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, sharing)
It should work now.