Hello World

1. 

   Creating a new NetBeans project.

   Steps to create the project:
   1. Run Netbeans.
   2. Click on the File menu, then select New Project.
   3. A new window will pop up. On the first page select "Java" from categories, and "Java Application" from projects. Then click next.
   4. Set Project Name to HelloWorld. Select a Project Location and Project Folder. These choices determine a directory where your work will be saved.
   5. Make sure Create Main Class is checked. Enter "HelloWorld" into the adjacent textbox. (This differs from the default.)
   6. The window should look similar to the one on this page. Click finish.

2. Editing the HelloWorld class.

   
   1. A window should be opened labeled HelloWorld.java.
   2. Enter the following code in the main function:
      

      System.out.println("Hello World!");
      

      Your screen should look as shown at right.
   3. Save the file using the menu: "File > Save".
   4. You should have noticed as you typed the period after System, NetBeans "helps" you. If you didn't notice this, play around with retyping it.

3. Running the program.

   The following two methods both run the program:
   1. To run the program from within NetBeans do the following. Select "Run > Run Main Project" from the menu.

      A sub-window should pop up and display the output of your program. It should look something like:
      

   2. To run the program from the command line (on a terminal) perform the following steps:
      1. Select "Run > Clean and Build Main Project" from the main menu bar.
      2. This has the effect of creating a ".jar" file. You can see the file by selecting the "Files" tab, then expanding down to the "HelloWorld/dist/" folder. See below, right.
         
      3. In a terminal (or command prompt) outside of NetBeans, change directories to "HelloWorld/dist/" part of your project. You can run the program with the following command:
         
         java -jar HelloWorld.jar

4. Discussion of Program.

   Source code with comments stripped out:

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

   Comments:
   • There is one method (or function) in this program, named main. The method only has one statement, which prints our message.
   • Statements end with semicolons.
   • Java programs begin by executing a main method.
   • The method main is part of the class HelloWorld. A class is a collection of functions and java objects, which haven't been introduced yet.
   • System is another class. It contains an object called out, which controls the output of the program. The object out is a member of a class with a method called println.

Helpful Links:

• The NetBeans IDE Java Quick Start Tutorial
• Oracle has several hello world tutorials, including one using NetBeans, one for using windows without NetBeans, and one for using the linux command line.
• Creating Your First Java Program: Tutorial for creating a "Hello World" program in Windows using a terminal window. Check this out if you have difficulty running the .jar file directly.

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This presentation is part of a Mathematical Research Oriented Java Tutorial, which aims to introduce students to the benefits that writing computer programs can provide to their understanding of mathematics.