Hollow Concentric Triangle with Numbers
This program prints hollow concentric triangles using numbers.
Problem Statement
Write a Java program that prints concentric hollow triangles with numbers up to 7 rows.
Source Code
| 1 | public class HollowConcentricTriangleNumbers { |
| 2 | public static void main(String[] args) { |
| 3 | int n = 7; |
| 4 | for(int i=1; i<=n; i++) { |
| 5 | for(int j=i; j<n; j++) System.out.print(" "); |
| 6 | for(int j=1; j<=2*i-1; j++) { |
| 7 | if(j==1 || j==2*i-1 || i==n) System.out.print(i); |
| 8 | else System.out.print(" "); |
| 9 | } |
| 10 | System.out.println(); |
| 11 | } |
| 12 | } |
| 13 | } |
Program Output
1
2 2
3 3
4 4
5 5
6 6
7777777777777
Explanation
The same hollow triangle logic is used but each row's boundary positions print its own row index instead of a star, so the triangle edges are labeled with numbers while the base row is fully filled with the final row's number.