Java Reference
In-Depth Information
JSeparator Class
The
JSeparator
class is a special component that acts as a separator on a
JMenu
. The
JPopupMenu
and
JToolBar
classes also support separators, but each uses its own subclass of
JSeparator
. In
addition to being placed on a menu, the
JSeparator
can be used anywhere you want to use a
horizontal or vertical line to separate different areas of a screen.
The
JSeparator
is strictly a visual component; therefore, it has no data model.
Creating JSeparator Components
To create a separator for a
JMenu
, you don't directly create a
JSeparator
, although you can.
Instead, you call the
addSeparator()
method of
JMenu
, and the menu will create the separator
and add the separator as its next item. The fact that it's a
JSeparator
(which isn't a
JMenuItem
subclass) is hidden. There's also an
insertSeparator(int index)
method of
JMenu
that allows
you to add a separator at a specific position on the menu, that isn't necessarily the next slot.
If you plan to use a
JSeparator
away from a menu (for example, to visually separate two
panels in a layout), you should use one of the two constructors for
JSeparator
:
public JSeparator()
JSeparator jSeparator = new JSeparator();
public JSeparator(int orientation)
JSeparator jSeparator = new JSeparator(JSeparator.VERTICAL);
These constructors allow you to create a horizontal or vertical separator. If an orientation
isn't specified, the orientation is horizontal. If you want to explicitly specify an orientation, you
use either of the
JSeparator
constants of
HORIZONTAL
and
VERTICAL
.
JSeparator Properties
After you have a
JSeparator
, you add it to the screen like any other component. The initial
dimensions of the component are empty (zero width and height), so if the layout manager of
the screen asks the component what size it would like to be, the separator will reply that it
needs no space. On the other hand, if the layout manager offers a certain amount of space, the
separator will use the space if the orientation is appropriate. For instance, adding a horizontal
JSeparator
to the north side of a
BorderLayout
panel draws a separator line across the screen.
However, adding a horizontal
JSeparator
to the east side of the same panel would result in
nothing being drawn. For a vertical
JSeparator
, the behavior is reversed: The north side would
be empty and a vertical line would appear on the east side.
The four properties of
JSeparator
are listed in Table 6-7.
Table 6-7.
JSeparator Properties
Property Name
Data Type
Access
accessibleContext
AccessibleContext
Read-only
orientation
int
Read-write bound
UI
SeparatorUI
Read-write bound
UIClassID
String
Read-only
