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Lesson 2: Installing Java, Compiling and Running Programs

In this lesson, we learn how to compile and run a simple Java program which just prints "Hello World!" to the console. (Lesson 01 is the introduction lesson with no examples, so we start here at 02 :-)

1. Installing Java

1.1. Under Ubuntu Linux

  • open console
  • type sudo apt-get update and press enter
  • type in your passoword if asked to
  • type sudo apt-get install openjdk-8-jdk and press enter
  • type in your passoword if asked to

1.2. Under Microsoft Windows

2. Verifying Installation

  • open console

  • type java -version

  • the output should be something like:

    $ java -version openjdk version "1.8.0_121" OpenJDK Runtime Environment (build 1.8.0_121-8u121-b13-0ubuntu1.16.04.2-b13) OpenJDK 64-Bit Server VM (build 25.121-b13, mixed mode)

3. Compile and Run Programs

We use a very simple example program here, a typical Hello World! program.



you get a file HelloWorld.class which can be executed in the Java VM.

Execute (after compiling):

java HelloWorld