Solved

java.lang.ClassNotFoundException (main class not found)

Posted on 2009-03-30
5
940 Views
Last Modified: 2013-12-15
Hi,

I was working with a 2D graphing example (actually got the example from here) and I was trying to plot some additional points .

After writing code to do so I noticed when running the program the code was stepping through the old code (ie not running sequentially, making bizarre jumps, etc)

So after some googling I decided to clean my project (Project --> Clean)

Now I'm getting an error that says the main class cannot be found, which is quite odd since it was working fine until I "cleaned" it.

I am using java 1.6 and the latest version of eclipse.  Below is my code.

Thanks !!

Bryan


import javax.swing.*;

import java.awt.*;

import java.util.*;
 

public class DrawGraphExam extends JFrame

{
 
 

    public DrawGraphExam()

    {

        super("Glove Data Representation");
 

        setSize(300,300);

        setDefaultCloseOperation(EXIT_ON_CLOSE);

        setLocationRelativeTo(null);
 

        Container c = getContentPane();

        c.setLayout(new BorderLayout());

        Graph gloveGraph = new Graph(getPoints());

        //c.add(new Graph(getPoints()));

        c.add(gloveGraph);

        gloveGraph.setPoint(10);

        //gloveGraph.drawPoint(g)

    }
 

    private HashMap getPoints()

    {

        HashMap points = new HashMap();

        points.put(new Integer(6), new Integer(5));

        points.put(new Integer(3), new Integer(3));

        points.put(new Integer(7), new Integer(4));

        points.put(new Integer(1), new Integer(7));

        points.put(new Integer(4), new Integer(2));

        return points;

    }
 

    public static void main(String[] args)

    {

    

        new DrawGraphExam().show();

    	System.out.println("test");

    	//DrawGraphExam gloveGraph  = new DrawGraphExam();

    	//gloveGraph.show();

    	System.out.println("test");

    }

    //public void plotPoint()
 

}
 

class Graph extends Canvas

{

    private HashMap points;

    private int x0;

    private int y0;

    private int b = 25;

    private int gap = 20;

    private int tw = 5;

    //begin berg's code

    private int xOld = 0;

    private int yOld = 0;

    private int xCurrent;

    private int yCurrent;

    //end berg
 

    public Graph(HashMap points)

    {

        this.points = points;

        setBackground(Color.white);

    }
 

    public void paint(Graphics g)

    {

        super.paint(g);

        drawLine(g);

        drawPoints(g);

        drawPoint(g);

    }
 

    public void drawLine(Graphics g)

    {

        Dimension d = getSize();

        x0 = b;

        y0 = d.height - b;
 

        Graphics2D g2 = (Graphics2D)g;

        g2.setColor(Color.blue);

        g2.setStroke(new BasicStroke(1.5f));
 

        g2.drawLine(x0, y0, d.width-x0, y0); // horizontal line

        g2.drawLine(x0, y0, x0, b); // vertical line

        

        int ticksY = (int) (y0 - b)/gap;

        int ticksX = (int) (d.width-2*x0)/gap;
 

        int yx = y0;

        for(int i=0; i<ticksY; i++) // draw vertical ticks

        {

            yx -= gap;

            g2.drawLine(x0, yx, x0-tw, yx);

            g2.drawString(String.valueOf(i*10), x0, yx);

        }
 

        int xx = x0;

        for(int i=0; i<ticksX; i++) // draw horizontal ticks

        {

            xx += gap;

            g2.drawLine(xx, y0, xx, y0+tw);

            g2.drawString(String.valueOf(i*10), xx, y0);

        }

    }
 

    public void drawPoint(Graphics g){

        Graphics2D g2 = (Graphics2D)g;

        g2.setColor(Color.RED);

        g2.setStroke(new BasicStroke(1f));

        g2.drawLine(xOld, yOld, xCurrent, yCurrent);

        System.out.println("drawing point at " + xOld);

       

    }

    public void setPoint(int y){

    	xCurrent = xOld + 10; // for now making increments of 5

    	yCurrent = y;

    }

    private void drawPoints(Graphics g)

    {

        if(points != null)

        {

            Graphics2D g2 = (Graphics2D)g;

            g2.setStroke(new BasicStroke(1f));

            ArrayList list = new ArrayList(points.keySet());

            Collections.sort(list); // sorts list of x-set

            Iterator xset = list.iterator();

            int x,y;

            int cX = -1, cY = -1;

            int r = 3;

            while(xset.hasNext())

            {

                Integer key = (Integer)xset.next();

                x = x0 + (key.intValue() * gap);

                y = y0 - (((Integer)points.get(key)).intValue() * gap);

                g.fillRect(x,y,r,r);

                if(cX > 0 && cY > 0)

                {

                    g.drawLine(cX, cY, x, y);

                }

                cX = x;

                cY = y;

            }

        }

    }

}

Open in new window

0
Comment
Question by:bryanberg
5 Comments
 
LVL 92

Expert Comment

by:objects
Comment Utility
check your java file is inside a source folder in your project
and make sure you are running the right class

0
 
LVL 15

Expert Comment

by:fsze88
Comment Utility
what's your classpath? missed classpath=.\;    ?
0
 
LVL 1

Expert Comment

by:Tavic
Comment Utility
It's a problem with your project or file names, not your code.  I can compile and run the code you provided just fine.
0
 
LVL 86

Accepted Solution

by:
CEHJ earned 500 total points
Comment Utility
>>
Now I'm getting an error that says the main class cannot be found, which is quite odd since it was working fine until I "cleaned" it.
>>

Just try rebuilding the project and running again
0
 

Author Closing Comment

by:bryanberg
Comment Utility
I had to remove the the source folder and than readd it in order to prompt the rebuild.  For some reason my code was not rebuilding on its own, eventhough I had the option selected to build automatically. Anyone had issues like this ?

Thanks !!
0

Featured Post

How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

Join & Write a Comment

Suggested Solutions

Title # Comments Views Activity
json example 39 110
Eclipse Neon start with Admin account only 6 44
The line on IDE 4 34
thymeleaf natural templating vs JSP 2 23
Are you developing a Java application and want to create Excel Spreadsheets? You have come to the right place, this article will describe how you can create Excel Spreadsheets from a Java Application. For the purposes of this article, I will be u…
Jaspersoft Studio is a plugin for Eclipse that lets you create reports from a datasource.  In this article, we'll go over creating a report from a default template and setting up a datasource that connects to your database.
Viewers will learn about arithmetic and Boolean expressions in Java and the logical operators used to create Boolean expressions. We will cover the symbols used for arithmetic expressions and define each logical operator and how to use them in Boole…
This video teaches viewers about errors in exception handling.

772 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

10 Experts available now in Live!

Get 1:1 Help Now