public boolean validateInput() {
		for(int i = 0; i < 9; i++) {
			for(int j = 0; j < 9; j++) {
				try {
					if(Integer.parseInt(entries[i][j].getText()) < 1) {
						return false;
					}
				}
				catch (NumberFormatException e) {
					JOptionPane.showMessageDialog(null, "Invalid input. Enter an integer at row "
													+ (i + 1) + " column " + (j + 1), "Error", JOptionPane.ERROR_MESSAGE);
				    return false;
				}
			}
		}
		return true;
	}