1
CMSC 433 – Programming Language
Technologies and Paradigms
Spring 2007
Flyweight Pattern
Apr. 05, 2007
2
Example
• We want to draw a small folder
icon with a name under it for
each person in a an
organization.
• We want two types of icons,
one for “is Selected” and one
for “not Selected.”
• We can have an icon objec t for
each person, with its own
coordinates, name and selected
state.
– Each icon can then draw()
itself.
• Lets code it.
3
Efficiency Issues
• If this is a large organization, there could be a
large number of such icons, but they are actually
all the same graphical image.
• Even if we have two icons, one for “is Selected”
and one for “not Selected” the number of different
icons is small.
• In such a system, having an icon object for each
person, with its own coordinates, name and
selected state is a waste of resources.
4
A “better” Approach
• Instead, we’ll create a
FolderFactory that returns
either the selected or the
unselected folder drawing
class, but does not create
additional instances once
one of each has been
created.
• Since this is such a simple
case, we just create them
both at the outset and then
return one or the other.
