Question

My assignment in my Java course is to make 3 triangles. One left aligned, one right aligned, and one centered. I have to make a menu for what type of triangle and then input how many rows is wanted. The triangles have to look like this

*
**
***
****


   *
  **
 ***
****


  *
 ***
*****

So far I was able to do the left aligned triangle but I can’t seem to get the other two. I tried googling but nothing turned up. Can anyone help? I have this so far.

import java.util.*;
public class Prog673A
{
    public static void leftTriangle()
    {
        Scanner input = new Scanner (System.in);
        System.out.print("How many rows: ");
        int rows = input.nextInt();
        for (int x = 1; x <= rows; x++)
        {
            for (int i = 1; i <= x; i++)
            {
                System.out.print("*");
            }
            System.out.println("");
        }
    }
    public static void rightTriangle()
    {
        Scanner input = new Scanner (System.in);
        System.out.print("How many rows: ");
        int rows = input.nextInt();
        for (int x = 1; x <= rows; x++)
        {
            for (int i = 1; i >= x; i--)
            {
                System.out.print(" ");
            }
            System.out.println("*");
        }
    }
    public static void centerTriangle()
    {

    }
    public static void main (String args [])
    {
        Scanner input = new Scanner (System.in);
        System.out.println("Types of Triangles");
        System.out.println("\t1. Left");
        System.out.println("\t2. Right");
        System.out.println("\t3. Center");
        System.out.print("Enter a number: ");
        int menu = input.nextInt();
        if (menu == 1)
            leftTriangle();
        if (menu == 2)
            rightTriangle();
        if (menu == 3)
            centerTriangle();
    }
}

Sample Output:

Types of Triangles
1.  Left
2.  Right
3.  Center
Enter a number (1-3):  3
How many rows?: 6

     *
    ***
   *****
  *******
 *********
***********

Answer 1

Hint: For each row, you need to first print some spaces and then print some stars.
The number of spaces should decrease by one per row, while the number of stars should increase.

For the centered output, increase the number of stars by two for each row.