Plot Program

[lsmitherman]

Hi guys. I'm new to java and signed up for a college java class and was assigned to create a plot program that places an * of a function at a point at execution. I keep getting an ArrayIndexOutOfBoundsException when i try to compile the program. here is the code i have so far. If anyone can help me debug it would be greatly appreciated. Btw I'm writing the code in Eclipse if that helps?

public class SmithermanProgram {

	public static void main(String[] args) {
		double a= Double.parseDouble(args[0]);
		double b= Double.parseDouble(args[1]);
		int n= Integer.parseInt(args[2]);
		int dx= (int)(b-a)/ n;
		int i;
		double x = 0, min = 0, max = 0, y, sf;
		for (i = 0;i <= n;);{
			x = a + i * dx;
			y = x;
		if (y > max)	
			max = y; i++;
		if (y < min)
			min = y; i++;
			}
		sf = 160/(max - min);
		{
			x = a + i* dx;
			y = x;
			double nSpaces = (y - min) * sf;
			int j = 0;
			
			if (j <= nSpaces)
				System.out.print(" ");
			else System.out.println("*"); i++;
				
		}
		System.out.println("a= " + a);
		System.out.println("b= " + b);
		System.out.println("n= " + n);
		System.out.println("dx= " + dx);
		System.out.println("min= " + min);
		System.out.println("max= " + max);
		System.out.println("sf= " + sf);

[Fubarable]

Hello and welcome to the forum. Your program is incomplete -- it's missing its bottom half. Also, which line causes the exception? Also, please use code tags when posting code (see my signature below).

Much luck!

[lsmitherman]

very sorry bout the code thing. It says the ArrayOutOfBoundsException is on the line of args[0]. And what do you mean the program is incomplete?

[Fubarable]

Also, this for loop is incorrect:

for (i = 0;i <= n;);{
   x = a + i * dx;
   y = x;
   //...
   i++

For one, that semicolon at first line just before the opening brace: ; { is going short circuit the loop. It means that no statement will occur within the loop body. Also, you'll want to increment "i" within that first line of the for loop. So don't do this:

    int i;
    for (i = 0; i <= n;);{
      x = a + i * dx;
      y = x;
      if (y > max)
        max = y;
      i++;
      if (y < min)
        min = y;
      i++;
    }

but instead something more like this:

    //int i;
    for (int i = 0; i <= n; i++){
      x = a + i * dx;
      y = x;
      if (y > max) {
        max = y;
      }
      //i++;
      if (y < min) { // always enclose if's else's for loops, while loops in braces
        min = y;
      }
      //i++;
    }

[Fubarable]

very sorry bout the code thing. It says the ArrayOutOfBoundsException is on the line of args[0]. And what do you mean the program is incomplete?

Then you're not calling your code with command line args. If you're not running the code on the command line but in eclipse, you'll have to tell eclipse to do this for you via it's Run - Run Configurations - Arguments menu item.

By incomplete, I see that your main method has no closing brace nor does the class. The class shows its beginning but not its ending.

You may want to start over on this one.

[lsmitherman]

ok thanks so much for the help!