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.Scanner;

public class Main
{
    public static void main(String[] args)
    {
        int n, line, asterik;
        Scanner key = new Scanner(System.in);
        System.out.println("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.print("*");
                }
            }
            else
            {
 
                for(asterik = n; asterik <= line && (asterik != 0); asterik--)
                {
                    System.out.print("*");
                }    
            }
            System.out.println(" ");
        }    
    }
}

[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]

@milk242
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--).