Java Reference
In-Depth Information
public void click()
{
door.setState(door.STAYOPEN);
}
public void timeout()
{
door.setState(door.CLOSING);
}
}
CHALLENGE 22.4
Write the code for
DoorClosing.java
.
The new design leads to much simpler code, but you might feel a bit dissatisfied that the
"constants" that the
Door
class uses are in fact local variables.
Making States Constant
Suppose that you decide to move the state constants to a
DoorConstants
interface. For this
approach to work, you have to eliminate the
Door
instance variable from the
DoorState
class. You can drop this variable by changing the
click()
,
complete()
, and
timeout()
transition methods in the
DoorState
class to require a
Door
object as an input parameter. In
this design, a
Door
object that receives, for example, a
click()
method from the carousel
forwards this call as
state.click(this)
.
