Objektorienteeritud programmeerimine (Narva Kolledž) - Kursused

First program

Once the environment is set up, write your first Java program - the traditional Hello World. The purpose of this program is to type the sentence Hello, World! on the monitor.

Step 1. Watch the video:

Step 2. Launch IntelliJ and start a new project. The wizard will ask you for a few names:

* Project Name - the name of a new project. This will be the name of the folder where all your current project files will be kept. We recommend to create a new project for each session, e.g. OOP.

* Class Name - the name of the class in the code stored in the src (source) folder within your IntelliJ project. NB! Class names must be unique, without spaces, and the first letter of each word must be a capitalised letter. We recommend to create a new class for each task, e.g. HelloWorld.

* Java File Name - the name of the file with extension of .java. IntelliJ sets the file name exactly as the class name, and holds the code.

Step 3. Type the following source codes - a text file that contains instructions written in a high level language Java. The source code cannot be executed (made to run) by a processor without some additional steps (translation into bytecode).

The following source code defines a class called "HelloWorld". DO NOT COPY the code because your mind and hands need time to get used to a new programming language!

PS! Pay attention:

Java is case-sensitive;
the file name must be the same as the class name;
punctuation: commas (,), dots (.), quotes ("), parentheses [({
in classes, methods, and other flow-control structures, code is always enclosed in paired curly braces { };
in Java, each code statement must end with a semicolon ;; but do not use semicolons after method and class declarations that follow with curly braces;
the highlighted "key words" - IntelliJ does it to make it easier for you to read your code.

Step 3. Compile/build the project and run the program (use the top menu):

PS! Pay attention to:

a Java source file must have the extension of ".java";
a compiled source code is a Java bytecode with extension of ".class".

Question:

Check the folder with your source code. Has a new file with extension of .class been added?

Keep the code:

public class HelloWorld {
  public static void main(String[] args) {
    System.out.println("Hello, World!");
  }
}

Session 1

Objektorienteeritud programmeerimine (Narva Kolledž) 2017/18 kevad