Ubuntu12.04 install and configure Java JDK

Configuring Java JDK in Ubuntu should be a required skill for every Java developer. Previously, it was always a rough configuration without summary or review. Let's summarize it today!

Some of the content in this article comes from the network, and the configuration process is prepared for use. The most classic part of this article is the switching method between multi-version JDK!

Installation

1. Uninstall the built-in OpenJdk

$  sudo apt-get purge openjdk*

2. After the JDK is installed and downloaded, the 64-bit Linux version officially provided by Oracle has the tar.gz format for JDK 1.7, but JDK 1.6 has the bin format. This document will record it in the. bin format.

$ Chmod + x jdk-6u45-linux-x64.bin # Add execution permissions $./jdk-6u45-linux-x64.bin # after running the JDK will be decompressed to the local directory

3. Check the result. Currently, there are two JDK versions in this directory, and 1.7 is installed previously.

$ lldrwxr-xr-x 8 john john     4096 Mar 27  2013 jdk1.6.0_45/drwxr-xr-x 8 john john     4096 Apr  4  2013 jdk1.7.0_51/

4. Create a JDK soft link and direct it to JDK 1.7.0 _ 51. You need to soft link that!

$ ln -s jdk1.7.0_51 currentjohn@ubuntu:Jdk$ lllrwxrwxrwx 1 john john        11 Feb  9 18:29 current -> jdk1.7.0_51/drwxr-xr-x 8 john john      4096 Mar 27  2013 jdk1.6.0_45/drwxr-xr-x 8 john john      4096 Feb  9 18:27 jdk1.7.0_51/

Configure Environment Variables

1. Modify system-level environment variables

$ sudo vim /etc/environment

2. Add the following content and modify it according to your own situation.

JAVA_HOME="/home/john/Developer/Jdk/current"CLASSPATH=".:$JAVA_HOME/lib"

3. Make the environment variable effective immediately after modification.

$ source /etc/environment 

Set the default Java parser

1. view the current default Java parser

$ update-alternatives --display java java - auto mode  link currently points to /usr/bin/gij-4.6/usr/bin/gij-4.6 - priority 1046  slave java.1.gz: /usr/share/man/man1/gij-4.6.1.gzCurrent 'best' version is '/usr/bin/gij-4.6'.

2. Add a Java parser

$ sudo update-alternatives --install /usr/bin/java java ~/Developer/Jdk/current/bin/java 300

3. Configure the default Java parser. Pay attention to the permissions. Select project 1 on the local machine for configuration.

$ sudo update-alternatives --config javaThere are 2 choices for the alternative java (providing /usr/bin/java).  Selection    Path                                       Priority   Status------------------------------------------------------------* 0            /usr/bin/gij-4.6                            1046      auto mode  1            /home/john/Developer/Jdk/current/bin/java   300       manual mode  2            /usr/bin/gij-4.6                            1046      manual modePress enter to keep the current choice[*], or type selection number: 1update-alternatives: using /home/john/Developer/Jdk/current/bin/java to provide /usr/bin/java (java) in manual mode.

4. Check whether the configuration options are correct after finishing the job!

The alternative mode has changed from automatic to manual!

$ update-alternatives --display java java - manual mode  link currently points to /home/john/Developer/Jdk/current/bin/java/home/john/Developer/Jdk/current/bin/java - priority 300/usr/bin/gij-4.6 - priority 1046  slave java.1.gz: /usr/share/man/man1/gij-4.6.1.gzCurrent 'best' version is '/usr/bin/gij-4.6'.

View Java version

$ java -versionjava version "1.7.0_51"Java(TM) SE Runtime Environment (build 1.7.0_51-b13)Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)

Thanks to the following authors for ranking in no particular order :)

Ubuntu Java installation Configuration

Ubuntu 12.04 uninstall the built-in OpenJDK, manually download the IDK and configure the Java Runtime Environment

Install the Java Development Environment on Ubuntu 12.04 (jdk1.7 + Eclipse)

Update-alternatives learning notes

Update-alternatives custom link pointing usage