Numbers - Java - page 169

try try {

result = Double . parseDouble ( aNumber );
System . out . println ( "Number is " + result );
} catch catch ( NumberFormatException exc ) {

System . out . println ( "Invalid number " + aNumber );
return return ;

}

}

Discussion

Of course, that lets you validate only numbers in the format that the designers of the wrapper
classes expected. If you need to accept a different definition of numbers, you could use regu-
lar expressions (see Chapter 4 ) to make the determination.

There may also be times when you want to tell if a given number is an integer number or a
floating-point number. One way is to check for the characters ., d , e , or f in the input; if one
of these characters is present, convert the number as a double . Otherwise, convert it as an
int :

public public class class GetNumber GetNumber extends extends Frame {

/** The input textField */
private

private TextField textField ;
/** The results area */
private

private TextField statusLabel ;

/** Constructor: set up the GUI */
public

public GetNumber () {
Panel p = new new Panel ();

p . add ( new new Label ( "Number:" ));

p . add ( textField = new

new TextField ( 10 ));
add ( BorderLayout . NORTH , p );
textField . addActionListener ( new new ActionListener () {

public public void void actionPerformed ( ActionEvent ev ) {

String s = textField . getText ();
statusLabel . setText ( process ( s ). toString ());

}

});
add ( BorderLayout . SOUTH , statusLabel = new

new TextField ( 10 ));

pack ();

}