Difference between revisions of "Installing Java"

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== More Information ==
 
== More Information ==
[http://docs.oracle.com/javase/ Java SE at Oracle.com]
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* [http://docs.oracle.com/javase/ Java SE at Oracle.com]
[http://en.wikipedia.org/wiki/Java_(programming_language) Wikipedia article]
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* [http://en.wikipedia.org/wiki/Java_(programming_language) Wikipedia article]
[http://docs.oracle.com/javase/tutorial/ Very informative tutorials]
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* [http://docs.oracle.com/javase/tutorial/ Very informative tutorials]
  
 
== Sources ==
 
== Sources ==

Revision as of 17:23, 28 October 2013

What is Java? What purpose does it serve?

Definition

"Java is a programming language and computing platform first released by Sun Microsystems in 1995. There are lots of applications and websites that will not work unless you have Java installed, and more are created every day. Java is fast, secure, and reliable. From laptops to datacenters, game consoles to scientific supercomputers, cell phones to the Internet, Java is everywhere!" (Oracle page on Java)

Installing java

Editing your make.conf

To tell portage that we would like java pulled in the next time it is updated, we need to do the following:

 # nano /etc/portage/make.conf

Running that command should present you with a file containing something similar to this:

File:Make conf example.png
An example make.conf

In the file, if it does not exist, create a line like the following:

USE="java"

Press Ctrl+X , then y, then enter to write the changes to the file.

Emerging java

To install java, run the following command:

 # emerge --ask --update --newuse --deep @world

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild  N     ] dev-java/java-config-wrapper-0.16  8 kB
[ebuild  N     ] sys-apps/baselayout-java-0.1.0  71 kB
[ebuild  N     ] dev-java/java-config-2.2.0-r1000:2  PYTHON_ABIS="2.7 3.3 -2.6 -3.1 -3.2 (-3.4)" 51 kB
[ebuild  N     ] app-admin/eselect-java-0.1.0  71 kB
[ebuild  N     ] dev-java/icedtea-bin-7.2.3.9:7  USE="X alsa cups -cjk -doc -examples -nsplugin -source" 47,781 kB
[ebuild  N     ] virtual/jdk-1.7.0:1.7  0 kB
[ebuild  N     ] virtual/jre-1.7.0:1.7  0 kB
Would you like to merge these packages? [Yes/No] yes

Testing to see if it emerged

To check that java installed on your system, run the following command:

java -version

If you get something like this, you are ready to use java!:

java version "1.7.0_21"OpenJDK Runtime Environment (IcedTea 2.3.9) (Gentoo build 1.7.0_21-b02)OpenJDK 64-Bit Server VM (build 23.7-b01, mixed mode)

Using the java command

Overview of the command

The java command can be run like so:

  • java [options] class [argument ...]
  • java [options] -jar file.jar [argument ...]

Example command usage

Compiling code:

$ javac -d bin -sourcepath src -cp lib/lib1.jar;lib/lib2.jar src/com/example/Application.java

Running code:

$ java -cp bin;lib/lib1.jar;lib/lib2.jar com.example.Application

Running a jarfile:

$ java -jar Application.jar

More Information

Sources

(Information provided for example command usage)