Help with this simple triangle program

[milk242]

I am trying to figure out how to print a triangle in the shape of this depending on the user input. If they input 4 the max height would be 4.
*
**
***
****
***
**
*

I have no idea how to print the triangle after it reaches its max height. So far my code is this. Please help!
import java.util.Scann er;
[code=java]
public class Main
{
public static void main(String[] args)
{
int n, line, asterik;
Scanner key = new Scanner(System. in);
System.out.prin tln("Please enter the size of the triangle you want");
n = key.nextInt();
for(line = 1; line <= n+(n-1); line++)
{
if(line <= n)
{
for(asterik = 1; asterik <= line; asterik++)
{
System.out.prin t("*");
}
}
else
{

for(asterik = n; asterik <= line && (asterik != 0); asterik--)
{
System.out.prin t("*");
}
}
System.out.prin tln(" ");
}
}
}[/code]

[JosAH]

You are trying to squeeze all your logic and control flow in one big loop that handles 2*n-1 lines. You have to test whether or not you're past half way. Why not implement two simple loops, one after the other, no nesting; the first loop handles the first n lines and the second one handles the last n-1 lines.

For convenience you should define a little method that prints i characters on a line; something like this:

private static void printLine(int i, char c) {
   for (int p= 0; p < i; p++)
      System.out.print(c);
   System.out.println();
}

In your two loops I described above you can simply call that little method and all those auxiliary loops that only take care of the printing are gone from your two loops.

kind regards,

Jos

[milk242]

Thanks Jos for the help that makes sense, but I was also wondering if its possible to do this task with only two for loops that are nested. I'm working out of a java book and it gives me a hint on using two for loops, one nested in another. I'm thinking its not possible because, how would you start the downward decrease of asterisk with only two loops?

[JosAH]

Thanks Jos for the help that makes sense, but I was also wondering if its possible to do this task with only two for loops that are nested. I'm working out of a java book and it gives me a hint on using two for loops, one nested in another. I'm thinking its not possible because, how would you start the downward decrease of asterisk with only two loops?

I'd do it like this:

for (int i= -3; i <= 3; i++) {
   int nofStars= 4-Math.abs(i);
   // print 'nofStars' on a line ...
}

... but I don't find it very intuitive.

kind regards,

Jos

[jkmyoung]

Would have used 2 for loops like

for(i = 1; i <=n; i++){
  //println i stars
}
for(i = n-1; i >0; i--){
  //println i stars
}

First loop increments and second loop decrements (i--).