Confused about this error.

Question

I'm new to Java, and I'm trying to do some work with the Graphics2d library. But whenever I try to run any sample code (like below), I get this weird error:
java.lang.NoClassDefFoundError: ShapeExample
Exception in thread "main"
What's up? It seems that the code below is fine. I'm using J2SE 1.4.1 with Eclipse.
import javax.swing.*; // For JPanel, etc.
import java.awt.*; // For Graphics, etc.
import java.awt.geom.*; // For Ellipse2D, etc.
/** An example of drawing/filling shapes with Java2D in Java 1.2.
* From tutorial on learning Java2D at
* http://www.apl.jhu.edu/~hall/java/Java2D-Tutorial.html
* 1998 Marty Hall, http://www.apl.jhu.edu/~hall/java/
public class ShapeExample extends JPanel {
private Ellipse2D.Double circle =
new Ellipse2D.Double(10, 10, 350, 350);
private Rectangle2D.Double square =
new Rectangle2D.Double(10, 10, 350, 350);
public void paintComponent(Graphics g) {
clear(g);
Graphics2D g2d = (Graphics2D)g;
g2d.fill(circle);
g2d.draw(square);
// super.paintComponent clears offscreen pixmap,
// since we're using double buffering by default.
protected void clear(Graphics g) {
super.paintComponent(g);
protected Ellipse2D.Double getCircle() {
return(circle);
public static void main(String[] args) {
WindowUtilities.openInJFrame(new ShapeExample(), 380, 400);
}

Answer 1

I am running it now without an IDE, can you guys
explain the problem a bit more explicitly? I mean, I
thought the class that is giving the trouble is the
ShapeExample class, which is in the file.
Do you mean to say that I have to put that part of
the file with this class in a seperate file (say
shapeexample.class) and then use a .java file to call
the class to run it?
Sorry, I'm pretty new at this.You write code that humans can understand and put it into .java files.
Then, you call javac, or click your IDE's "Compile" or "Build" button to compile the .java source files into .class files that the VM can understand.
Then you call java -cp some;class;path MyClass, or click your IDE's Run button, to invoke the VM and tell it to run the main method in the MyClass.class file, and that it can find MyClass.class and all the other .class files that it needs in some or class or path (where "some" and "class" and "path" are just dummy placeholder example type thingies)
You should go through a tutorial from the beginning. All these questions will be addressed.
See Resources for beginners at http://www.thejword.com/3.html#beginner_resources