Thread: How can I add a user input into a 2D- array and print it?

//THIS IS THE CODE I HAVE SO FAR:
 
import java.util.Arrays;
import java.util.Scanner;
import java.io.File;
import java.io.FileWriter;
import java.awt.event.KeyEvent;
import javax.swing.JOptionPane;
 
 
public class GridInput {
        static int X = 6;
        static int Y = 7;
public static void main(String[]args) {
String [][] Grid = new String [X][Y];
 
System.out.println("Hello R, please make your move! Choose a number from 0-6");
int R = StdIn.readInt();
 
        System.out.print("  ");  
        for (int i = 0; i <= X; i++) {
                if (i > 0) {           
                    System.out.print(i - 1);
                }
                for (int j = 0; j < Y; j++) {
                    if (i == 0)
                        System.out.print(j + " ");
                    else;
                        System.out.print(Grid[i-1][j] = " *");
                }
        System.out.println();
            }
        }
}

//WHAT I WANT TO PRINT LOOKS LIKE THIS (SAY USER INPUT FOR R IS "4"):

0 1 2 3 4 5 6
0 * * * * * * * *
1 * * * * * * * *
2 * * * * * * * *
3 * * * * * * * *
4 * * * * * * * *
5 * * * * * R * *

//THEN THERE SHOULD BE ANOTHER USER INPUT WHICH CHANGES THE GRID AGAIN.
//IF THE SECOND USER INPUT IS 4 AGAIN:

0 1 2 3 4 5 6
0 * * * * * * * *
1 * * * * * * * *
2 * * * * * * * *
3 * * * * * * * *
4 * * * * * R * *
5 * * * * * R * *

//I WANT THE GRID TO LOOK EXACTLY LIKE THIS

USER INPUT FOR R IS "4"

Can you explain how a user input of "4" can be used to place an "R" at a specific row and column in a 2 dim array?

I WANT THE GRID TO LOOK EXACTLY LIKE THIS

Please explain how the row and column for placing the "R" is computed?

The user picks the row

Did you mean column?

Ok, I think I understand. What problems are you having placing the "R" in the array?

I mean Row (horizontal/ above)

I don't understand how a user picking a row puts a value in a column. How does the program pick the column?

The bottom display of a filled in grid in post#2 shows the "R"s in column 4 not in row 4.

how to place "R" into the array

Use an assignment statement:

  theArray[row][column] = theValue;

he program should then automatically place R in the bottom column of that row

That is confusing.
For me: Rows are horizontal (left, right) and columns are vertical(up, down).
There isn't a bottom column of a row. There is a bottom row of a column.

O ok, I think I understand. Yeah rows (left, right) and columns (up, down).

Anyway, what I mean should happen is like this for example: (Ignore the awkward spacing - just tried to make it easier to read)

1. The user's first input is 1, then the following happens and is printed:

   0    1    2   3    4    5    6
0  *    *    *   *    *    *    * 
1  *    *    *   *    *    *    * 
2  *    *    *   *    *    *    *  
3  *    *    *   *    *    *    *  
4  *    *    *   *    *    *    *  
5  *    R    *   *    *    *    *

2. Then the user inputs 4:

   0    1    2   3    4   5   6
0  *    *    *   *    *   *   * 
1  *    *    *   *    *   *   * 
2  *    *    *   *    *   *   *  
3  *    *    *   *    *   *   *  
4  *    *    *   *    *   *   *  
5  *    R    *   *    R   *   *

3. If the user then inputs 4 again:

   0    1    2   3   4   5   6
0  *    *    *   *   *   *   * 
1  *    *    *   *   *   *   * 
2  *    *    *   *   *   *   *  
3  *    *    *   *   *   *   *  
4  *    *    *   *   R   *   *  
5  *    R    *   *   R   *   *

Now, I have no idea how to code for that to happen
or what this piece of code means:

 theArray[row][column] = theValue;

Thanks for listening to me try to explain.

what this piece of code means:

 theArray[row][column] = theValue;

theArray - the name of the array
row - the row index (an int)
column - the column index (an int)
= - an assignment statement
theValue - the value to be assigned to the 2 dim array at location: row, column

The tutorial: https://docs.oracle.com/javase/tutor...ts/arrays.html

for that to happen

Before trying to write any code, work out the logic.
Can you explain how you would do it manually? Given an input from a user and a grid with the 0,0 point to the top left, what would you need to do to put a "R" on the grid? What simple steps would you take?
And then later when there are some "R"s already on the grid, what do you need to do to add another "R"?

print the "changed" array?

Create a method that prints the array.
Then call it whenever the array has been changed.

First I would add this:

You need to work out the logic before writing code.
What if there is already an "R" in the bottom row?

can just create another method any time

Yes. That is the usual way to write programs - create methods for jobs that are done repeatedly.

When it something is already in the bottom row,

Will the logic start at the bottom and work towards the top
or will it start at the top and work towards the bottom?

I will have to change the grid accordingly

Ok, what are the details for that? The computer does not understand "accordingly", you will have to explicitly work out the details.