Java Reference
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The main advantage of this solution is that it requires only one class, and thus
it is very compact. On the other hand, adding a new behaviour requires modifica-
tion in several points of the class: a new constant and a new case in the switch
construct. As a result the code is more difficult to understand and to maintain.
The second solution embeds each behaviour in a different class. The main class
must have an attribute that refers to the object implementing the currently
selected behaviour. All the different behaviour classes implement the common
interface Behavior . In other words, the main class can be linked to any object that
conforms to the contract in the Behavior interface.
The binding of the interface to a specific behaviour is carried out at run time.
This is in the nature of polymorphism.
``` Interface ppp
! perform()
! setBehavior()
! doPerform()
! doPerform()
The above classes can be implemented as follows:
public class Changing {
Behavior behavior # null ;
public void setBehavior(Behavior newBehavior)
{ behavior # newBehavior; }
public void perform(){
if (behavior ! # null )
public interface Behavior{
void doPerform();
public class FirstBehavior implements Behavior {
public doPerform(){/* B1 */ }
public class SecondBehavior implements Behavior {
public doPerform(){/* B2 */ }
The following code fragment shows the use of this solution:
Changing chObject # new Changing(;
chObject.setBehavior( new FirstBehavior());
The main advantage of this approach is that adding a new behaviour is just a
matter of defining a new class; this means that the main class is independent of
the different behaviours. On the other hand, this approach uses many more
classes making it more complex.
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