swing - java Checker board issues -

so have program asks user number of rows , columns , makes checker board issue works odd numbers if user put in 9 , 9 again display checkered board if number inputted shows columns of white , black

import javax.swing.*; import java.awt.*;  public class checkers {      public static void main(string[] args) {         jframe thegui = new jframe();         thegui.settitle("checkers");         string inputstr = joptionpane.showinputdialog("number of rows");         if (inputstr == null) return;         int rows = integer.parseint(inputstr);         inputstr = joptionpane.showinputdialog("number of columns");         if (inputstr == null) return;         int cols = integer.parseint(inputstr);         thegui.setsize(cols * 50 , rows * 50);         thegui.setdefaultcloseoperation(jframe.exit_on_close);         container pane = thegui.getcontentpane();         pane.setlayout(new gridlayout(rows, cols));         (int = 1; <= rows * cols ;i ++) {             if(i % 2 == 0){               colorpanel panel = new colorpanel(color.white);               pane.add(panel);             }else{                 colorpanel panel = new colorpanel(color.black);                 pane.add(panel);             }         }         thegui.setvisible(true);     }  } 

your example identifies numbers in single loop. instead, use nested loops identify alternating tiles:

g.setcolor(color.lightgray); … (int row = 0; row < h; row++) {     (int col = 0; col < w; col++) {         if ((row + col) % 2 == 0) {             g.fillrect(col * tile, row * tile, tile, tile);         }     } } 

a complete example seen here.