Unit 11 Interfacesand Abstract Classes GEOCITIESws单元11接口和抽象类geocitiesws.pptVIP

Interfaces and Abstract Classes- What are they?- How are they used?- Where will we use them?- Calling superclass’ constructors and methods Calling Superclass’s Constructors Calling Superclass’s Constructors (cont’d) One of the superclass’s constructors is always called, but you don’t have to have an explicit super statement. Calling Superclass’s Constructors (cont’d) Superclass’s constructor calls its superclass’s constructor, and so on, all the way up to Object’s constructor. Calling Superclass’s Methods AP Computer Science A – Healdsburg High School Abstract Class – A class which at least one of the methods is left “abstract”, or without the code implemented. public abstract class Polygon { private int numberOfSides; public Polygon() { /* code not shown */ } public abstract double getArea(); /* other methods not shown */ } Abstract Class – A class which at least one of the methods is left “abstract”, or without the code implemented. public abstract class Polygon { private int numberOfSides; public Polygon() { /* code not shown */ } public abstract double getArea(); /* other methods not shown */ } public class Rectangle extends Polygon { private double myLength; private double myWidth; public Rectangle() { /* code not shown */ } public double getArea() { return myLength * myWidth; } /* other methods not shown */ } Example: Inheritance Diagram for GridWorld’s Grid AbstractGrid BoundedGrid UnboundedGrid Abstract Grid Class Subclasses of AbstractGrid Interface – A construct in Java where everything is left “abstract”. Interfaces have no constructors, instance variables, nor program code. public interface Fillable { void fill(int x); int getCurrentAmount(); int getMaximumCapacity(); } Interface – A construct in Java where everything is left “abstract”. Interfaces have no constructors, instance variables, nor program code. public interface Fillable { void fill(int x); int getCurrentAmount(); int getMaximumCapacity(); }