import java.text.DecimalFormat; // for formatting doubles
import uwcse.io.*;

/**
 * Practicing using loops
 */

public class Loops {
	public static void main(String[] args) {
		new Loops().figuresOfStars();
	}

	/**
	 * Check that the sum of the cubes is the square of the sum
	 * <p>
	 * 
	 * i.e. (^ means exponentiation (not available in java)) <br>
	 * 1^3 + 2^3 + 3^3 + ... + n^3 = (1 + 2 + 3 + ... + n)^2 <br>
	 * Use a loop to allow the user to test the formula with several values of
	 * n. Exit the loop if n is not a positive integer.
	 */
	public void sum3vsSum2() {
		int n;
		Input input = new Input();
		System.out.println("Sum of the cubes / square of the sum");

		do { // Input n until n<=0
			n = input.readInt("Enter an integer (<=0 to quit): ");

			int sum = 0; // sum
			int sumCubes = 0; // sum of the cubes

			// Compute sum and sumCubes
			// use a for loop
			for (int i = 1; i <= n; i++) {
				sumCubes += i * i * i;
				sum += i;
			}
			if (n > 0)
				System.out.println("Sum of the cubes: " + sumCubes
						+ "\nSquare of the sum: " + sum * sum);
		} while (n > 0);
	}

	/**
	 * Display shapes of stars
	 * <p>
	 * In a console window, display the following shapes using for loops
	 * 
	 * <pre>
	 * *         *
	 * **       **
	 * ***     ***
	 * ****   ****
	 * </pre>
	 * 
	 * Allow the user to select the number of lines. Repeat the process until
	 * the user inputs a non positive value for the number of lines.
	 */
	public void figuresOfStars() {
		int n;
		Input input = new Input();
		System.out.println("Display of stars");

		do {
			n = input.readInt("Enter a positive integer (or <=0 to quit): ");
			for (int j = 1; j <= n; j++) {
				// print j stars
				for (int i = 1; i <= j; i++) {
					System.out.print("*");
				}
				// print 2n - 2j spaces
				for (int i = 1; i <= 2 * n - 2 * j; i++) {
					System.out.print(" ");
				}
				// print j stars
				for (int i = 1; i <= j; i++) {
					System.out.print("*");
				}
				// next line
				System.out.println();
			}
		} while (n > 0);

	}

	/**
	 * Sum the digits of a positive integer
	 * <p>
	 * Let the user enter an integer.<br>
	 * If the integer is positive, sum all of the digits of the integer. Repeat
	 * the process until you get a single digit answer:<br>
	 * for instance, 123456 gives 21 which gives 3<br>
	 * Repeat the process until the user inputs a non positive value for the
	 * integer.
	 */
	public void sumDigits() {
		int n;
		Input input = new Input();
		System.out.println("Sum the digits");

	}

	/**
	 * Rolling a die
	 * <p>
	 * Let the user enter an integer n. Roll a dice n times and display how many
	 * times each face comes out.<br>
	 * Repeat the process until the user enters a non positive value for n.
	 */
	public void rollADie() {
		int n;
		Input input = new Input();
		System.out.println("Roll a die");

	}
}