1. Polymorphism Polymorphism - Greek for “many forms”
A superclass that using a superclass variable to reference a subclass method.
Example:
Shape s = new Circle();
s.getArea();
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2. Dynamic Binding A polymorphic method Late binding or dynamic binding
A method that has multiple meanings
Created when a subclass overrides a method of the superclass
Late binding or dynamic binding
The appropriate version of a polymorphic method is decided at execution time
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3. Dynamic Binding Figure 9-7a
area is overridden: a) mySphere.DisplayStatistics( ) calls area in Sphere
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4. Dynamic Binding Figure 9-7b
area is overridden: b) myBall.displayStatistics( ) calls area in Ball
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5. Dynamic Binding
Controlling whether a subclass can override a superclass method
Field modifier final
Prevents a method from being overridden by a subclass
public final boolean writeDatabaseRecord() { … }
Field modifier abstract
Requires the subclass to override the method
public abstract int getCount();
Early binding or static binding
The appropriate version of a method is decided at compilation time
Used by methods that are final or static
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6. Dynamic Binding and Abstract Classes
Overloading methods
To overload a method is to define another method with the same name but with a different set of parameters
The arguments in each version of an overloaded method determine which version of the method will be used
Example:
public void printDetails(Person p) { … }
public void printDetails(Elephant e) { … }
public void printDetails(Car c) { … }
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7. Things to know Difference between overloading and overriding
How polymorphism is implemented and what version of the method gets called.
Difference between static binding and dynamic/late binding
What a “final” method means
What an “abstract” method means
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