Diamond with nested for loop in Java

Question

I am trying to display a diamond of asterisks using nested for loops.

Here is my code so far:

public          


        

Answer 1

java-11

By using String#repeat, introduced as part of Java-11, you can do it with a single loop.

public class Main {
    public static void main(String[] args) {
        int size = 9;
        int midRowNum = size / 2 + 1;
        for (int i = 1 - midRowNum; i < midRowNum; i++) {
            System.out.println(" ".repeat(Math.abs(i)) + "*".repeat((midRowNum - Math.abs(i)) * 2 - 1));
        }
    }
}

Output:

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

By increasing the amount of space by one character, you can also print a variant of the diamond:

public class Main {
    public static void main(String[] args) {
        int size = 9;
        int midRowNum = size / 2 + 1;
        for (int i = 1 - midRowNum; i < midRowNum; i++) {
            System.out.println("  ".repeat(Math.abs(i)) + "* ".repeat((midRowNum - Math.abs(i)) * 2 - 1));
        }
    }
}

Output:

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