Swing II - Java - page 968

The dispose Method
The method dispose is a method in the class JFrame that releases any resources
used by the JFrame or any of its components. So, a call to dispose eliminates the
JFrame and its components, but if the program has items that are not compo-
nents of the JFrame , then the program does not end. For example, in Display
18.2 the smaller window of the class ConfirmWindow invokes dispose (if the user
clicks the "No" button). That causes that smaller window to go away, but the
larger window remains.

dispose

The dispose Method
The class JFrame has a method named dispose that will eliminate the invoking JFrame
without ending the program. When dispose is invoked, the resources consumed by the
JFrame and its components are returned for reuse, so the JFrame is gone, but the program
does not end (unless dispose eliminates all elements in the program, as in a one-window
program). The method dispose is often used in a program with multiple windows to elimi-
nate one window without ending the program.
SYNTAX

JFrame_Object .dispose();

The JFrame_Object is often an implicit this . A complete example of using dispose can be
seen in Display 18.2.

PITFALL: Forgetting to Invoke setDefaultCloseOperation

If you register a window listener to respond to window events from a JFrame , you
should also include an invocation of the method setDefaultCloseOperation , typi-
cally in the JFrame constructor. This is because the default or other behavior set by
setDefaultCloseOperation takes place even if there is a window listener. If you do
not want any actions other than those provided by the window listener(s), you
should include the following in the JFrame constructor:

setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);

If you do not include any invocation of setDefaultCloseOperation , the default
action is the same as if you had included the following invocation

setDefaultCloseOperation(JFrame.HIDE_ON_CLOSE);

which hides the JFrame when the close-window button is clicked. (The actions of
any registered window listener are also performed.)

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