Hi everybody,

I am new to Java, and can't figure out why my program is not recognizing the class Picture. The program compiles, but when I run it, it gives an error:

Exception in thread "main" java.lang.NoClassDefFoundError: Picture
at NewtonReal.main(NewtonReal.java:55)

Please note that to run NewtonReal, you must include three command-line arguments, such as -20 40 20.

Thanks in advance if you can help.

Here's the code:

import java.awt.*;
public class NewtonReal {
     * Executes Newton's method on the function x*x*x-1, until either
     * max iterations have occurred or the current guess changes by
     * less than eps.
     * @param x0  initial guess for a cube root of 1
     * @param max maximum number of iterations before stopping
     * @param eps "epsilon" tolerance: when guess changes by less than
     *            eps, assume it has stabilized
     * @return the number of iterations executed

    public static int newton(double x0, int max, double eps) {

        double xnew = 0;
        int numIter = 0;
        while (numIter < max){
            if (3*x0*x0 == 0){
                return 0;
            xnew = x0 - (x0*x0*x0-1)/(3*x0*x0);
            if (Math.abs(xnew - x0) < eps){
                return numIter;
            x0 = xnew;
        return numIter;
    public static void main(String[] args) {

        double X_MIN = Double.parseDouble(args[0]);
        double X_WIDTH = Double.parseDouble(args[1]);
        int MAX_ITER = Integer.parseInt(args[2]);

        int PX_HEIGHT = 512;
        int PX_WIDTH = 512;
        double Y_HEIGHT = 40;
        double EPS = 1.0e-6;
        double X_MAX = X_MIN + X_WIDTH;
	double x = X_MIN;
        double xStep = (double)(X_WIDTH / PX_WIDTH);
        double yStep = (double)(Y_HEIGHT / PX_HEIGHT);
        Picture pic = new Picture(PX_WIDTH, PX_HEIGHT);
        while (x < X_MAX){
            int numIter = newton(x, MAX_ITER, EPS);
            double xCord = Math.ceil((double)(0 - X_MIN)/X_WIDTH*PX_WIDTH);
            double yCord = Math.ceil(511 - (double)(numIter/Y_HEIGHT)*512);
            int i = (int)xCord;
            int j = (int)yCord;
            x = x + xStep;

I have search the java.awt package and didn't find the class Picture:

I don't believe that it is a class that the JDK has. Try search it in the internet and you will find plenty Picture classes implemented by others

OK thanks. I realized the problem was with my CLASSPATH.