import javax.swing.*;

/**
 *
 * Class NumericInputParser provides two static methods to parse would-be
 * numeric input entered in a text field.  One method parses any integer, the
 * other method parses for an integer in a given range.  If the input doesn't
 * parse, the method complains in a GUI dialog.
 *
 */
public class NumericInputParser {

    /**
     * Call Integer.parseInt to parse the given string-valued number.  If it
     * parses, return the Integer.  If the input value does not parse as an
     * Integer, display an error dialog and return null.
     *                                                                      <p>
     * The return value of this method is an Integer rather than an int.  In
     * this way, the method can use a null value to indicate that the user
     * input did not parse as a number.
     */
    public static Integer parse(String number) {
        try {
            return Integer.parseInt(number);
        }
        catch (NumberFormatException e) {
            JOptionPane.showMessageDialog(null, "Illegal input value",
                "", JOptionPane.ERROR_MESSAGE);
            return null;
        }
    }

    /**
     * Do parse, then ensure that the number is in given start,end range,
     * inclusive.
     */
    public static Integer parseInRange(String number, int start, int end) {
	Integer i = parse(number);
	if (i == null) {
	    return null;
	}
	if (i >= start && i <= end) {
	    return i;
	}
	else {
            JOptionPane.showMessageDialog(null, "Illegal input value",
                "", JOptionPane.ERROR_MESSAGE);
            return null;
        }
    }

}