Printing A Diamond Shape In Java, Based On User Input

Question

I have a problem with a program I am trying to write. A user inputs a positive odd integer, otherwise the program prompts the user until they do. When they do, the program print

Answer 1

A user inputs a positive odd integer, otherwise the program prompts the user until they do

You need to scan in a loop

do
{
    userInput = keyboard.nextInt(); 
    if (userInput % 2 == 0)
        System.out.println("That is not an Odd Integer!");            
    if(userInput < 0)
        System.out.println("That is not a Positive Odd Integer");
} while(userInput < 0 || userInput %2 == 0);

Now you can remove that validation else if (userInput%2 == 1){

Now the first thing I realize when checking at your loop is if (row+col==userInput-1 || ) which won't compile as you have a comparison operator with nothing following.

Note that you can replace System.out.print("\n"); with System.out.println("") but that's not really important...

Now replace your loop condition so that they start as 0

for (int row = 0; row <= userInput; row++){
        for (int col = 0; col <= userInput; col++ ){

Now since you want a Diamond, you need to have 4 diagonal, so 2 loops (one for top and bottom)...

for (int i = 1; i < userInput; i += 2)//Draw the top of the diamond
{
    for (int j = 0; j < userInput - 1 - i / 2; j++)//Output correct number of spaces before
    {
        System.out.print(" ");
    }
    for (int j = 0; j < i; j++)//Output correct number of asterix
    {
        System.out.print("*");
    }

    System.out.print("\n");//Skip to next line
}

for (int i = userInput; i > 0; i -= 2)//Draw the bottom of the diamond
{
    for (int j = 0; j < userInput -1 - i / 2; j++)
    {
        System.out.print(" ");
    }

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

    System.out.print("\n");
}

So the final code would look like this

public static void main(String[] args)
{
    Scanner keyboard = new Scanner(System.in);
    System.out.println("Welcome to the drawing program:");
    System.out.println("Please Input a Positive Odd Integer:");
    char userAnswer;
    int userInput;
    do
    {
        userInput = keyboard.nextInt();
        if (userInput % 2 == 0)
        {
            System.out.println("That is not an Odd Integer!");
        }
        if (userInput < 0)
        {
            System.out.println("That is not a Positive Odd Integer");
        }
    } while (userInput < 0 || userInput % 2 == 0);

    for (int i = 1; i < userInput; i += 2) //This is the number of iterations needed to print the top of diamond (from 1 to userInput by step of two for example with 5 = {1, 3, 5} so 3 rows.
    {
        for (int j = 0; j < userInput - 1 - i / 2; j++)//write correct number of spaces before, example with 5 = j < 5 - 1 -i / 2, so it would first print 4 spaces before, with 1 less untill it reach 0
        {
           System.out.print(" ");//write a space
        }
        for (int j = 0; j < i; j++)
        {
            System.out.print("*");//write an asterix
        }

        System.out.println("");
    }

    // Same logic apply here but backward as it is bottom of diamond
    for (int i = userInput; i > 0; i -= 2)
    {
        for (int j = 0; j < userInput -1 - i / 2; j++)
        {
            System.out.print(" ");
        }

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

        System.out.print("\n");
    }

}