Graphics, AWT, Swing II part

if it is not, do text=text.trim() to remove spaces,

then check text.equals("") to see if it is an empty String

Lucio Benfante, Arnaud Berger and Jorge Jordao

 Q: Whats the difference between a Frame and a canvas? Can someone tell me

the difference?

Answer:

A Frame is , well , a frame   a window, with borders,close/minimize/maximize buttons

(usually), and can not contain other elements, such as a menubar ,buttons panels,

etc.

a Canvas is a user interface element (which you can place in e.g. a frame) onto

which you can draw/display something..

by Nils O. Selasdal

 Q: I know how to make a text box using Visual Basic that can only accept certain

keys for example if I wanted to make a box where you can type only numbers in it or

letters. However, when it comes to Java I have not been able to figure this out. Is

there a way to do this and make a textbox where you can only type letters in it?

Answer: First of all,  ASCII  is not a synonym for  text . ASCII is just one of many ways

of encoding text to numeric values. It is 7 bit and only includes values from 0 through

127.

Now, on to your question. With ASCII,  numbers  and  letters  are a little easier to

check, since the only letters are  A   Z  and  a   z . However, Java uses Unicode and

has all sorts of fun extra characters.

But you do have a few handy methods on the java.lang.Character class such as

isDigit and isLetter

Now, if you are using swing, then to achieve what I m guessing you want is quite

simple. Just hook a custom text document to the JTextField you re using and have it

do the filtering.

** Here s the part of The Java Tutorial that goes over it

http://java.sun.com/docs/books/tutorial/uiswing/components/textfield.html#validation

Here s someone s Swing FAQ on that

http://users.vnet.net/wwake/swing/faq.html#text_check

Here s a JavaWorld article that describes how to do that to limit the length of input.

Shouldn t be too hard for you to change to your specific needs.

http://www.javaworld.com/javaworld/javaqa/2000 05/02 qa 0512 textbox_p.html

All these links were from the first page of a search on http://www.google.com

Google is your friend!

John A.Cruz

 Q: How can I force Java not to draw the background?

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