How to install Java in Centos 5 and 6

How to install Java in Centos 5 and 6

First you need to Download Archive File from oracle.

Download latest version of java from http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html

Install JAVA using Alternatives

After extracting java archive file, you just need to set up to use newer version of java using alternatives using the follwoing commands.

# cd /usr/src/jdk1.7.0_65/
# alternatives –install /usr/bin/java java /opt/jdk1.7.0_65/bin/java 2
# alternatives –config java

There are 4 programs which provide ‘java’.

Selection Command
———————————————–
* 1 /usr/lib/jvm/jre-1.6.0-openjdk/bin/java
+ 2 /opt/jdk1.7.0_55/bin/java
3 /opt/jdk1.7.0_60/bin/java
4 /opt/jdk1.7.0_65/bin/java

Enter to keep the current selection[+], or type selection number: 4 [Press Enter]
Now you may also required to setup javac and jar commands path using alternatives

# alternatives –install /usr/bin/jar jar /opt/jdk1.7.0_65/bin/jar 2
# alternatives –install /usr/bin/javac javac /opt/jdk1.7.0_65/bin/javac 2
# alternatives –set jar /opt/jdk1.7.0_65/bin/jar
# alternatives –set javac /opt/jdk1.7.0_65/bin/javac

Check JAVA Version

Use following command to check which version of java is currently being used by system.

# java -version
java version “1.7.0_65”
Java(TM) SE Runtime Environment (build 1.7.0_65-b17)
Java HotSpot(TM) Client VM (build 24.60-b09, mixed mode)

Setup Environment Variables

Most of java based application’s uses environment variables to work. Use following commands to set up it.

Setup JAVA_HOME Variable

# export JAVA_HOME=/opt/jdk1.7.0_65

Setup JRE_HOME Variable

# export JRE_HOME=/opt/jdk1.7.0_65/jre

Setup PATH Variable

# export PATH=$PATH:/opt/jdk1.7.0_65/bin:/opt/jdk1.7.0_65/jre/bin

You can follow above steps to install multiple version of java as same time, but you can use only one version at a time.

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