Wsrtjtyk

Hey I really need help with a program for my java programming class. I'll put in the instructions and the code I have thus far. Any help would be appreciated! Thanks in advance!!
Instructions:
Write a program called Box (Box.java) that will print/displays a hollow box shape
using asterisks (*). The program will read in an even number in the range 2 to 24 to
specify the number of rows/columns in the box. Display an error and re-prompt for
the number if an incorrect value was entered. The program will then display a hollow
of the appropriate size. Hint: Use loops within loops.
basically it should make a square box, so if you give it the number boxSize = 5 the output is a box with dimensions 5x5. the outline is made of asterisks but the inside is empty

heres what I have code wise so far

import java.util.Scanner;



public class Box

{



    public static void main(Stringargs)

    {

        //numrows and numcols are equal however the spacing is differnt

        Scanner input = new Scanner(System.in);

        System.out.print("Enter an even number (2-24):  ");

            int boxSize = input.nextInt();



        int numRows = boxSize;

        int numCols = numRows;

        // This program demonstrates compound decisions with the logical and operator &&

        //asks if the number is less than or equal to 24 and greater than or equal to 2 and that the remainder is 0 

        //when divided by 2, checks if its an even number like it should be



        if(boxSize >= 2 && boxSize <= 24 && boxSize%2 == 0)

        {   

            //nested loops are used to print out the asterisk in the correct pattern

            for(int r = 0; r<numRows; r++)

            {

                    System.out.println("*");

                for(int c = 0; c<numCols; c++)      

                {   

                            System.out.print("*");    

                }

                    }

        }

    }



            //This program demonstrates compound decisions with the logical or ( || ) operator

        //checks if any of the following are true

        //if one or more is true then that means that it is an incorrect number

        //then reprompts the user to put in a new number then checks again

        if(boxSize<2||boxSize>24||boxSize% 2 != 0)

        {

            System.out.println("Value must be an even number from 2-24");

        }

Basically my problem is I don't know what to put in the loops and where to get the shape. I also don't know how to make it REPROMPT for a boxSize value again if the number is odd or not between 2 and 24 and it also needs to display the error message that value must be between 2 ans 24, and even ect.

Your approach with nested loops is basically fine. Just the stuff inside is not quite what you are looking for.... What you want is more like this:

for(int r = 0; r<numRows; r++) {

    for(int c = 0; c<numCols; c++) {

        // print a "*" ONLY IF on border, and " " otherwise 

    }

    // here you finished printing the "*"/" ", so print just a newline

}

for promting and reprompting I would use a do {} while(yourIfCondition) loop, to reshow the prompt.

Here. I put all of it in one method. Notice there's so many ifs. You can optimize by using the ternary operator if you have reached that part in your course.

public static void main(String...args){

        int boxSize = 0;

        Scanner input = new Scanner(System.in);



        do {

            System.out.print("Enter box size [-1 to quit] >> ");

            boxSize = input.nextInt();



            if(boxSize == -1){

                System.exit(0);

            }



            /* check if number is valid */

            if(boxSize < 2 || boxSize > 24 || boxSize % 2 != 0){

                System.err.println("--Error: please enter a valid number");

                continue; // prompt again

            }



            // draw the box

            for (int col = 0; col < boxSize; col++) {

                for (int row = 0; row < boxSize; row++) {

                    /* First or last row ? */

                    if (row == 0 || row == boxSize - 1) {

                        System.out.print("*");

                        if (row == boxSize - 1) {

                            System.out.println(); // border reached start a new line

                        }

                    } else { /* Last or first column ? */

                        if (col == boxSize - 1 || col == 0) {

                            System.out.print("*");

                            if (row == boxSize - 1) {

                                System.out.println();

                            }

                        } else {

                            System.out.print(" ");

                            if (row == boxSize - 1) {

                                System.out.println();

                            }

                        }

                    }

                }

            }



        }while (true);

    }