Swing I - Java - page 942

There is also a constructor with one additional String parameter for the string ini-
tially displayed in the text area. For example:

JTextArea theText = new JTextArea("Enter\ntext here.", 5, 20);

Note that a string value can be multiple lines because it can contain the new-line char-
acter '\n' .
A JTextField has a similar constructor with a String parameter, as in the following
example:

JTextField ioField =
new JTextField("Enter numbers here.", 30);

If you look at Display 17.12, you will see that both JTextField and JTextArea
are derived classes of the abstract class JTextComponent . Most of the methods for
JTextField and JTextArea are inherited from JTextComponent and so JTextField
and JTextArea have mostly the same methods with the same meanings except for
minor redefinitions to account for having just one line or multiple lines. Display
17.18 describes some methods in the class JTextComponent . All of these methods are
inherited and have the described meaning in both JTextField and JTextArea.
You can set the line-wrapping policy for a JTextArea using the method setLine-
Wrap . The method takes one argument of type boolean . If the argument is true , then
at the end of a line, any additional characters for that line will appear on the following
line of the text area. If the argument is false , the extra characters will be on the same
line and will not be visible. For example, the following sets the line wrap policy for the
JTextArea object named theText so that at the end of a line, any additional characters
for that line will appear on the following line:
theText.setLineWrap( true );

setLineWrap

You can specify that a JTextField or JTextArea cannot be written in by the user.
To do so, use the method setEditable , which is a method in both the JTextField
and JTextArea classes. If theText names an object in either of the classes JTextField
or JTextArea , then the following
theText.setEditable( false );

output-only
setEditable

will set theText so that only your GUI program can change the text in the text
component theText ; the user cannot change the text. After this invocation of set-
Editable , if the user clicks the mouse in the text component named theText and
then types at the keyboard, the text in the text component will not change.
To reverse things and make theText so that the user can change the text in the text
component, use true in place of false , as follows:
theText.setEditable( true );

If no invocation of setEditable is made, then the default state allows the user to
change the text in the text component.