Installing Java

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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

Options

On Funtoo, there are several different java packages that you can emerge:

  • virtual/jre - When you emerge this, it pulls in the java runtime environment for your current profile.
  • virtual/jdk - When you emerge this, it pulls in the java development kit for your current profile.

Emerging java

To install java, run the following command:

 # emerge -av virtual/jdk

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)