Question

In Java:

Get an integer n from an input dialog or the console window (with user input), print out the following pattern on the console window (you may refer to displaying number-pyramid example shown in class).

For example, when n is 3, there are 5 rows in total.

              *

***

           *****

             ***

               *

When n is 4, there are 7 rows in total.

              *

            ***

          *****

        *******

          *****

            ***

Answer 1

import java.util.Scanner;

public class PrintDiamond {
   public static void main(String[] args) {
       Scanner sc = new Scanner(System.in);
       System.out.println("Enter n: ");
       int n = sc.nextInt();
       printDiamondPattern(1, n);
   }

   public static void printDiamondPattern(int thisRow, int num) {
       // the termination condition
       if (thisRow == num * 2)
           return;

       // the number of spaces
       int numberOfSpaces = 0;
       if (num < thisRow) {
           // finds the number of spaces
           numberOfSpaces = thisRow - num;
       } else {
           numberOfSpaces = num - thisRow;
       }

       // finds number of stars
       int numberOfStars = num - numberOfSpaces;

       // generate the string before printing it
       StringBuffer outputBuffer = new StringBuffer(num);
       for (int i = 0; i < numberOfSpaces; i++) {
           outputBuffer.append(" ");
       }
       for (int i = 0; i < numberOfStars; i++) {
           outputBuffer.append("* ");
       }

       // printing the string
       System.out.println(outputBuffer.toString());

       // recursion
       printDiamondPattern(thisRow + 1, num);
   }
}

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