From BlueJ to NetBeans
SWC 2.semester
Why change…?

BlueJ is great for introduction to
programming
◦ Simple interface, few options
◦ Graphical interface to classes and objects
◦ Some tehnical details are hidden
Why change…?

NetBeans is great for professional
programming
◦
◦
◦
◦

Much more functionality
Better editor, debugger,…
Integration to database systems
A full-blown, stand-alone system
…but also more complex!
What is NetBeans?
NetBeans is an open-source project
 Originates from SUN Microsystems
 www.netbeans.org
 Can - of course – be downloaded for free
from the website
 We use NetBeans 6.9.1 SE (+ Java JDK)

What is NetBeans?
How do I…
…create a new project?
 …add a new class?
 …edit a class definition?
 …write text to the screen?
 …get input from the user?
 …run a project?

Create a new project - BlueJ
Choose Project |
New Project…
Create a new project - BlueJ
Enter project name,
press ”Create”
Create a new project - NetBeans
Choose File |
New Project…
Create a new project - NetBeans
In Categories,
choose ”Java”
In Projects,
choose ”Java
Application”
Create a new project - NetBeans
Enter project
name and
location
Create a new project - NetBeans
Create a new project - NetBeans
Why is there a ”Main.java” class…?
 All Java programs must contain a method
with this signature:

public static void main(String[] args)
This was hidden in BlueJ!
 Think of Main as a ”System” class
 When the program starts, the code in the
main(…) method is executed

Add a new class- BlueJ
Press ”New Class…”
Enter class name
Add a new class- BlueJ
Add a new class- NetBeans
Highlight the
bankaccount
package!
Choose New |
Java Class
Add a new class- NetBeans
Enter class name
Add a new class- NetBeans
Edit a class definition - BlueJ
Double-click on the
class icon
Edit a class definition - BlueJ
Edit a class definition - NetBeans
Double-click on the
class icon
Edit a class definition - NetBeans
Note the file panes
in NetBeans
Edit a class definition - NetBeans
Why do red lines start to appear in the code,
as soon as I start typing…?
 The NetBeans editor continuously makes
an analysis of the code, even before it is
compiled
 The editor highlights errors in the code
by a waved red line, even before typing
has been completed
 Helpful…? Annoying…?

Edit a class definition - NetBeans
Yes, I know, but I
am still typing!!
Edit a class definition - NetBeans
See hints by
hovering mouse
over (!)
Edit a class definition - NetBeans
Why do lists with method names pop up
when I type…?
 The NetBeans editor supports ”autocompletion”, i.e. it tries to predict what
you will type next
 Typically when calling a method with ”.”
 Helpful, when you get used to it…

Edit a class definition - NetBeans
Available methods
on the specific
object/class
Documentation for
each method
Writing text to the screen - BlueJ
Writing text to the screen - BlueJ
Writing text to the screen - NetBeans
Writing text to the screen - NetBeans
Need this code for
actually executing
the method
Writing text to the screen - NetBeans
Output written to the
”Output window”
Get input from the user - BlueJ
Get input from the user - BlueJ
Enter parameter
value directly
Get input from the user - NetBeans
Not quite as simple to get input from a
user in NetBeans
 Two options

◦ Use the Scanner class
◦ Use a input dialog class

See chapter 3.6 in Big Java for details
Get input from the user - NetBeans
import java.util.Scanner;
…
Scanner in = new Scanner(System.in);
…
String name = in.nextLine();
…
int balance = in.nextInt();
…
double area = in.nextDouble();
Get input from the user - NetBeans
import javax.swing.JOptionPane;
…
String value =
JOptionPane.showInputDialog(”Limit”);
…
int limit = Int.parseInt(value);
Running a project - BlueJ
We cannot as such ”run” a project in
BlueJ – what should run..?
 We usually create a ”system” class, that
has a ”run”-like method

◦ Create a System object
◦ Right-click the object
◦ Call the run method
Running a project - NetBeans
Choose Run | Run
Main Project
Running a project - NetBeans
…or just click
the green triangle
(or press F6)
Running a project - NetBeans
Running a project always executes the
main method in the Main class!
 A project is automatically compiled when
you save it
 No reason to run a project in order to fix
syntax errors

Other NetBeans features
A GUI Builder – build a GUI by drag-drop
of controls. Code is auto-generated
 A much more powerful debugger
 More customisable
 Easy integration to database systems
 We will talk about additional features
later on…
