使用扫描仪和嵌套的 for 循环在 java 中创建一个空心矩形

Question

I am very stuck on this, I have created a program in Java to make a hollow rectangle but instead i get a full rectangle. The assignment has us create a new java class called 'Rectangle' and code the necessary material in there and then call the class and constructor in the main code. I have attached my code below. I realize that my System.out.print is being coded to print a blank space, i did this because when i had it print my 'drawChar' it looked outrageous. I just wanted it to look like a rectangle when i was asking for help.

This is my Rectangle Class:

public class Rectangle {
    private int width;
    private int height;
    private char drawChar;

    public Rectangle(int width,int height, char drawChar)
    {
        this.width = width;
        this.height=height;
        this.drawChar=drawChar;
    }


    public void printOutline()
    {
        for(int i=0; i<height; i++)
        {
            for(int j =0; j<width; j++)
            {
                System.out.print(drawChar);
                if(i==1||i>=height-1||j==0||j==width-1){
                    System.out.print(" ");
                }
                else{
                    System.out.print(" ");
                }
            }
            System.out.println();
        }
    }
}

and this is the main program:

public class Question1 {

    public static void main(String[] args) {
        Scanner keyboard = new Scanner(System.in);
        System.out.println("Enter a character: ");
        String input = keyboard.nextLine();
        char drawChar = '*';
        if(input.length() > 0 )
            drawChar = input.charAt(0);
        System.out.println("Please enter the width: ");
        int width = Integer.parseInt(keyboard.nextLine());

        System.out.println("Please enter the height: ");
        int height = Integer.parseInt(keyboard.nextLine());

        Rectangle rec = new Rectangle(width,height,drawChar);
        rec.printOutline();

    }
}

This is my result:

Enter a character: 
!
Please enter the width: 
5
Please enter the height: 
5
! ! ! ! ! 
! ! ! ! ! 
! ! ! ! ! 
! ! ! ! ! 
! ! ! ! ! 

Also, here is the assignment:

 *
 * Write a Rectangle Class with three fields and has a constructor with three parameters,
 *   - integers: width and height
 *   - character: drawChar
 *   Write Setters and Getters (even though you won't use them)
 * The class will have a method called printOutline that prints a rectangle to the
 * console that is the outline based on the dimensions width and height.
 * The method will use the character drawChar as its outline character. The method
 * should use nested for loops to print the output.
 * (HINT: Try to get the output to print a full rectangle without the spaces in the middle,
 * then alter your code to just print the character on the outline - think about your nested for-loops and what
 * values should have a character print or a space print.)
 *
 * The main method will demonstrate this class by asking the user for width, height and
 * a draw character.
 * (HINT: use charAt(0) method to get character from input String)
 * It will call the constructor with these values and then
 * draw a rectangle outline to the console.
 * Input Validation: Do not allow the user to enter negative numbers for height and width.
 * Loop until they enter a positive value.
 *
 * Example Output 1:
 * Please enter a character for your drawing:
 * $
 * Please enter a positive integer width:
 * 4
 * Please enter a positive integer height:
 * 5
 *
 * $$$$
 * $  $
 * $  $
 * $  $
 * $$$$
 *
 * Example Output 2:
 * Please enter a character for your drawing:
 * !
 * Please enter a positive integer width:
 * -1
 * INVALID - enter a positive integer width:
 * 6
 * Please enter a positive integer height:
 * -8
 * INVALID - enter a positive integer height:
 * 10
 *
 * !!!!!!
 * !    !
 * !    !
 * !    !
 * !    !
 * !    !
 * !    !
 * !    !
 * !    !
 * !!!!!!
 *

normally i would seek direction from my instructor but due to the covid-19 pandemic our campus is shut down and instruction has been pushed to online. I have been trying various solutions with no avail. Any suggestions would be greatly appreciated.

Answer 1

I'd tackle this first by breaking the problem into steps. You know you want the first row to print characters equal to the width. So start with that: print the character iteratively using your for loop (and finish with a println):

// always start with a complete row
for (int i = 0; i < width; i ++) {
    System.out.print(drawChar);
}
    System.out.println();

Next, you know you want the second through to second last rows to print the character, followed by spaces, followed by the character:

// for next set of rows, only print first and last
for (int j = 1; j < height; j ++) {
    // print the first one
    System.out.print(drawChar);
    // print the spaces
    for (int k = 1; k < width - 1; k ++) {
        System.out.print(" ");
    }
    // print the last one
    System.out.print(drawChar);
    System.out.println();
}

Then finish by printing the full row again (as you did for the first row).

To cut back the redundant code, you can start to build it into conditions. For example, if it's the first or last row:

// print conditionally, depending on row number
for (int i = 0; i < height; i ++) {
    // print a complete row if it's the first or last row
    if (i == 0 || i == height - 1) {
        for (int j = 0; j < width; j ++) {
            System.out.print(drawChar);
        }
        System.out.println();
    } 

You can build up from there to ensure that your conditions are accurately represented. I think you have your row and column logic mixed up in your conditional expression.

for (int i = 0; i < height; i ++) {
    for (int j = 0; j < width; j ++) {
        // if in the first or last row or first or last column, print character
        if(i == 0 || i == height - 1 || j == 0 || j == width - 1) {
            System.out.print(drawChar);
        } else {
            // otherwise print space
            System.out.print(" ");
        }
        // at end of row, start new line
        if (j == width - 1) {
            System.out.println();
        }
    }
}