Untitled

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("Enter a number: ");
        int R = scanner.nextInt();

        for (int i = 1; i <= R; i++) {
            // Print the beginning spaces
            for (int sp = 1; sp <= i - 1; sp++) {
                System.out.print(" ");
            }

            // Iterating from ith column to last column
            int lastCol = (R * 2 - (2 * i - 1));

            // To iterate through column
            for (int j = 1; j <= lastCol; j++) {
                if (i == 1 || j == 1 || j == lastCol) {
                    System.out.print("*");
                } else {
                    System.out.print(" ");
                }
            }

            // Next line
            System.out.println();
        }
    }
}