for(int i=0; i<btn.length; i++){
        	for(int j=0; j<btn.length;j++){
        		btn[i][j] = new Button(""+i+","+""+j);
        		btn[i][j].setPrefSize(50, 50);
        		// Adding button to GridPane, i representing column value, j  repsrenting row value.
        		gridPane.add(btn[i][j], i, j);
        		}
        }