Question

I have to write a program that takes a command-line argument n and prints out a pattern with alternating spaces and asterisks (as demonstrated below). Use at least two nested for loops and a constructor to achieve the pattern (an image is shown below of how it’s suppose to look).

This is the code I have tried already and no luck. I understand how to do this with a single for loop, but not a nested. I am also unsure how to integrate a constructor with this program.

This is how the image should look: * * * *
                                    * * * *
                                   * * * *
                                    * * * *
public class Box {
     public static void main(String[] args) {

         for (int i=1; i<2; i++) {
             System.out.println("* " + "* " + "* " + "* ");

             for (int j=0; j<i; j++) {
                 System.out.print(" *" + " *" + " *" + " *");

             }
         }
     }
 }

Answer 1

Slight modification to Bohemian’s answer. The outer for-loop is responsible for printing the rows. The inner loop prints the repeated characters on each row. The constructor simply sets the n field, which controls how many rows you print out. The main method creates a new object and invokes its only method.

public class Box {

private static int n; 

public Box(int n){
    this.n = n;
}

public static void doMagic() {
    for (int row = 0; row < n; row++) {
        if(row%2==1)
            System.out.print(" ");
        for (int col = 0; col < n; col++) {
            System.out.print("* ");
        }
        System.out.println();
    }
}
   public static void main(String[] args) {
    new Box(4).doMagic();
 } 
}