Are Composition and Inheritance the same? If I want to implement the composition pattern, how can I do that in Java?
Inheritance brings out IS-A relation. Composition brings out HAS-A relation.
Strategy pattern explain that Composition should be used in cases where there are families of algorithms defining a particular behaviour.
Classic example being of a duck class which implements a flying behaviour.
public interface Flyable{
public void fly();
}
public class Duck {
Flyable fly;
public Duck(){
fly = new BackwardFlying();
}
}
Thus we can have multiple classes which implement flying eg:
public class BackwardFlying implements Flyable{
public void fly(){
Systemout.println("Flies backward ");
}
}
public class FastFlying implements Flyable{
public void fly(){
Systemout.println("Flies 100 miles/sec");
}
}
Had it been for inheritance, we would have two different classes of birds which implement the fly function over and over again. So inheritance and composition are completely different.