Thread: Sierpinski's Triangle in Graphics

those last two errors.

Please explain.
Post the full text of the error messages here.

Please Edit your post and wrap your code with
[code=java]
<YOUR CODE HERE>
[/code]
to get highlighting

Where are the variables: dx and dy defined? The compiler can not find them in scope where they are used in the code.

You have many locally defined variables with those names. Their definitions go away when the code exits the surrounding {}s.
Define the variables at the same level (within the same pair of {}s) as where you are trying to use them.

I'm guessing lines 53/4 are these:

int x4 = x - dx / 2;
int y4 = y - dy / 2;

The compiler message is saying that it has no clue what the variables dx and dy. Possible reasons are that you made a typo and the spelling is wrong (difficult with such small names - but still possible since you might have declared them as DX and DY), or that you didn't declare them at all.

So go back and see how (and whether) you declared them.

-----

In most programming languages variables don't last for ever. And that's a good thing because it means we can reuse variables. But it does mean we have to worry about scope. The scope of a variable is just which parts of the code you can use the variable. Outside this region the variable is said to "go out of scope" and you will get the compiler's "Cannot find symbol" if you use that variable.

In Java the scope is easy to determine: start from wherever the variable is declared, the scope will extend until the closing } of that block. Eg

while(true) {
    int foo = 42;
 
    if(foo == 666) {
        System.out.println("???");
    } // <-- this } doesn't count because it matches the { above
 
    System.out.println(foo); // ok, foo is "in scope"
} // <-- this } is the closing } of the block where foo is declared
 
System.out.println(foo); // bad!: foo is "out of scope" aka "Cannot find symbol"

There are no errors but it's still not working! All that pops up are the words "Sierpinski's Triangle". Help again por favor?

import java.awt.*;
import java.awt.Color;
import javax.swing.JFrame;
import java.awt.Polygon;
import java.util.Random;
 
public class Sierpinski extends Canvas
{
    public void paint( Graphics z )
    {
    	Random flippin_tables = new Random();
 
		for( int n = 1; n <= 50000; n = n+1 )
		{
			int x = 512;
			int y = 382;
			int x1 = 512;
			int y1 = 109;
			int x2 = 146;
			int y2 = 654;
			int x3 = 876;
			int y3 = 654;
 
   			int r = flippin_tables.nextInt(255);
   			int g = flippin_tables.nextInt(255);
   			int b = flippin_tables.nextInt(255);
 
			Color COOL = new Color(r,g,b);
			z.setColor(COOL);
			z.drawLine(x,y,x,y);
 
			for( int q = 1; q <= 100000; q = q+1 )
			{
			}
			int oh_MY = 1 + flippin_tables.nextInt(3);
 
			if ( oh_MY == 1 )
			{
				int dx = x-x1;
				int dy = y-y1;
 
				int x4 = x - dx / 2;
				int y4 = y - dy / 2;
 
				z.drawLine(x4,y4,x4,y4);
				z.drawString("Sierpinski Triangle", 462,484);
			}
			else if ( oh_MY == 2 )
			{
				int dx = x-x2;
				int dy = y-y2;
 
				int x4 = x - dx / 2;
				int y4 = y - dy / 2;
 
				z.drawLine(x4,y4,x4,y4);
				z.drawString("Sierpinski Triangle", 462,484);
			}
			else if ( oh_MY == 3 )
			{
				int dx = (x-x3);
				int dy = y-y3;
 
				int x4 = x - dx / 2;
				int y4 = y - dy / 2;
 
				z.drawLine(x4,y4,x4,y4);
				z.drawString("Sierpinski Triangle", 462,484);
			}
		}
 
	}
 
    public static void main(String[] args)
    {
        JFrame win = new JFrame("Sierpinski");
        win.setSize(1024,768);
        win.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        win.add( new Sierpinski() );
        win.setVisible(true);
    }
 
}

it's still not working!

What do you expect the program you have written to do?
The only thing I see it doing is that it draws a String and a line in three different places.
What is not working about that String and that line that is drawn?

Do you have any specific questions about your assignment?

One change you should make to your code is move move the drawing to after the the values of x4, and y4 are computed and only do it once and not three times, like you had in post #1.

error because it can not find the variables dx and dy.

Define the variables dx and dy in the same place you have defined all the other variables.

why it is not forming triangles like it's supposed

Where does your code form a triangle? I only see where it draws a line.