Write a program that reads an integer and displays, using asterisks a filled and hollow square, placed next to each other. for example if side length is 5 the program should display like so.

This program prints a filled and hollow square.
Enter the length of a side: 5

* *
* *
* *

Here is the JAVA program.

import java.util.Scanner; //Scanner class to take input from user

 public class HollowFilledSquare {

          public static void main(String[] args) { //start of main() function body

    Scanner sc= new Scanner(System.in); // Scanner class object

          System.out.print("Enter an integer to display a filled and hollow square "); //prompts user to enter an integer

           int n = sc.nextInt(); // reads integer input from the user

          StringBuilder filled = new StringBuilder(n);

// creates objects filled and hollow of class StringBuilder

          StringBuilder hollow = new StringBuilder(n);

          for (int i = 1; i <= n; i++) { // outer loop for length of the square

              for (int j = 1; j <= n; j++) { // inner loop for width of square

                  filled.append("*"); //displays asterisks

                    if (i == 1 || i == n || j == 1 || j == n) // condition to display stars

                       {hollow.append("*");}

                   else

                     {  hollow.append(" ");  }             } // to display empty spaces

           System.out.println(filled + "   " + hollow);

// places hollow and filled squares next to each other

           filled. delete(0, filled.length());  

//removes characters from 0 to the length of filled square

           hollow. delete(0, hollow.length());      

//removes characters from 0 to the length of hollow square }}  }

Explanation:

The program first prompts the user to enter an integer. It uses outer loop for length of the square and inner loop for width of square in order to display the asterisks. append () function is used to display the sequence of asterisks. delete () function removes the  asterisks from the sequence of asterisks. String Builder is a class used for to create a string of n characters. It basically works like String but this is used to create modifiable objects.

The screen shot of the code along with the output is attached.