Please help me with this Java programming

Hello everyone I am a BSC Mathematics student and very beginner in Java Programming and as part of my Mathematics degree I am also learning Algorithm with Java programming. I am in very early stages of Java so I could be making very silly mistake but believe it or not but I am stuck with this error for last 2 days but still cannot figure out where is the problem. Anyone please help me I will really appreciate that.

Following is the programme code I am using:

Code :

---

import java.io.*;
import javagently.*;
class diy130
{
public static void main (String [] args) throws IOException
{
/* This java program plots the function y = 3 + x^2 from
x = 0 to x = 10 with delta x = 0.01. */
Graph y = new Graph("y = 3 + x^2", "x", "y");
double x;
y.setSymbol(true); y.setColor(y.red);
y.setTitle("y = 3 + x^2");
for (int i = 0; i <= 100; i++ )
{
x = i/10.0;
y.add(x, 3+Math.pow(x,2));
}
y.showGraph();
System.out.println("CTRL-C to end the program.");
}
}

---

Examine carefully the above program and make sure you understand every java statement. Now change the function to some other functions and plot the corresponding curves.

Code :

---

import java.io.*;
import javagently.*;
class diy131
{
public static void main (String [] args) throws IOException
{
/* This java program plots the function y = 3 + x^2 from
x = 0 to x = 10 with delta x = 0.01. */
Graph y = new Graph("y = 3 + x^2", "x", "y");
double[] x;
double[] fx;
x = new double [101];
fx = new double [101]; // We need 101 data boxes to hold the data below.
y.setSymbol(true); y.setColor(y.red);
y.setTitle("y = 3 + x^2");
for (int i = 0; i <= 100; i++ )
{
x[i] = i/10.0;
fx[i] = 3+Math.pow(x[i],2);
y.add(x[i], fx[i]);
}
y.showGraph();
System.out.println("CTRL-C to end the program.");
}
}

---

The data kept in x[i] and fx[i] may be used at a later stage of the program. Now add in java statements to the above program to print the data x[i] and fx[i] as two columns of numbers each allow four decimal places and a space between the data. Store the resulting program as diy132.java[/SIZE]

Graph isn't a standard Java SE class, do you have the code for that? Without it, there's no way for us to tell where the problem is.

Also, what is the problem that you are getting?