1. Computer Science [3] Java Programming II - Laboratory Course Lab 1 + 2: Review inheritance & abstract Review inheritance & abstractPolymorphism Faculty of Engineering & IT Software Engineering Department WWW.PALINFONET.COM Eng.Omar Al-Nahal Eng.Omar Al-Nahal

2. Inheritance What the importance of inheritance? public class Student { private String name; private String idNum; private String gender; private double mark; public Student (String name,String idNum, String gender, double mark){ this.name=name; this.idNum=idNum; this.gender=gender; this.mark=mark; } public void setName(String name){ this.name=name;} …. … public String getName(){ return name; } … …. }

3. Inheritance (cont) public class Employee { private String name; private String idNum; private String gender; private double salary ; public Employee (String name,String idNum, String gender, double salary){ this.name=name; this.idNum=idNum; this.gender=gender; this.salary=salary; } public void setName(String name){ this.name=name;} …. … public String getName(){ return name; } … …. }

4. Inheritance (cont) Inheritance (cont)

5. public class Person { private String name; private String idNum; private String gender; public Person (String name,String idNum, String gender){ this.name=name; this.idNum=idNum; this.gender=gender; } public void setName(String name){ this.name=name;} …. … public String getName(){ return name; } … …. } public class Student extends Person { private double mark; public Student (String name, String idNum, String gender, double mark){ super (name, idName, gender); this.mark=mark; } public void setMark(double mark){ this.mark=mark;} public double getMark( ){ return mark;}} public class Employee extends Person { private double salary; public Employee (String name, String idNum, String gender, double salary){ super (name, idName, gender); this. salary=salary; } public void setSalary(double salary){ this. salary=salary;} public double getSalary( ){ return salary;}} Inheritance (cont) Inheritance (cont)

6. SuperClass SubClass Is–a relation

7. Inheritance (cont) public class Student extends Person { private double mark; public Student (String name, String idNum, String gender, double mark){ super (name, idName, gender); this.mark=mark; } public void setMark(double mark){ this.mark=mark;} public double getMark( ){ return mark;} } public class Person { private String name; private String idNum; private String gender; public Person (String name,String idNum, String gender){ this.name=name; this.idNum=idNum; this.gender=gender; } public void setName(String name){ this.name=name;} public String getName(){ return name; } …. … public String toString(){ return "The name of the person is "+ getName();} } Student st=new Student(“noor”,”11”, ”female”,90.0); System.out.println (st. toString()); The name of the person is noor

8. Inheritance (cont) public class Person { private String name; private String idNum; private String gender; public Person (String name,String idNum, String gender){ this.name=name; this.idNum=idNum; this.gender=gender; } public void setName(String name){ this.name=name;} public String getName(){ return name; } …. … public String toString(){ return "The name of the person is"+getName();} } public class Student extends Person { private double mark; public Student (String name, String idNum, String gender, double mark){ super (name, idName, gender); this.mark=mark; } public void setMark(double mark){ this.mark=mark;} public double getMark( ){ return mark;} public String toString(){ return super.toString()+". Her mark is "+getMark(); } } Student st=new Student(“noor”,”11”, ”female”,90.0); System.out.println (st. toString()); The name of the person is noor. Her mark is 90.0

9. Inheritance (cont) Overloading deals with multiple methods in the same class with the same name but different signatures. Ex: public int operation( int x); public int operation (int x,int y); public int operation( double x); public int operation (String x,int y); public int operation (int x,String y); public double operation( int x); Overriding deals with two methods, one in a parent class and one in a child class, that have the same signature. b All classes are derived from the Object class. public class Person { private String name; …. } public class Person extends Object { private String name; …. }

10. Inheritance (cont) Abstract method: which have no code. Public abstract int getArea(); Abstract class: which have abstract methods and concrete methods. public abstract class Shape{ private String name; public Shape ( String name){ this.name=name; } public abstract String getName(); public abstract double getArea(); } An abstract class cannot be instantiated.Shape sh=new Shape(“ccc”); If class inherit abstract class, it must override all abstract methods

11. Inheritance (cont) public class Circle extends Shape{ private double r; public Circle ( double r){ super(“Circle”); this.r=r; } public String getName(){ return “Circle”;} public double getArea(){ Return Math.PI*r*r;} } public class Rectangle extends Shape{ private double height; private double width; public Circle ( double h,double w){ super(“Rectangle”); height=h; width=w; } public String getName(){ return “Rectangle”;} public double getArea(){ Return height*width; } }

12. Inheritance (cont) public class Test{ public static void main (String args[]){ Circle C=new Circl1(2.5); Rectangle R=new Rectangle(4.0,5.0); System.out.println( “The shape name is “+C.getName()+ “with Area”+C.getArea(); System.out.println( “The shape name is “+R.getName()+ “with Area”+R.getArea(); } Now Try…

13. b Polymorphism means many forms or many shapes. b A variable of a superclass type can reference an object of a subclass type Polymorphism Animal CatDogRabbit Animal anim1=new Animal(); Animal anim2 = new Cat(); Animal anim3=new Dog(); Animal anim4=new Rabbit(); Cat c= new Animal();

14. Dog Move() Polymorphism (cont) Cat Move() Animal Move() Rabbit Move() Animal anim2 = new Cat(); Anim2.move();

15. Dog move() Polymorphism (cont) Cat move() eat() Animal Move() Rabbit move() Animal anim2 = new Cat(); anim2.move(); anim2.eat(); Animal anim2 = new Cat(); If(anim2 instanceOf Cat){ Cat C1 =(Cat) anim2; C1.eat();}

16. public class Test{ public static void main (String args[]){ Shape sh[]=new Shape[2]; sh[0]=new Circl1(2.5); sh[1] =new Rectangle(4.0,5.0); for( int i=0;i<sh.length;i++) System.out.println( “The shape name is “+sh[i].getName()+ “with Area”+sh[i].getArea(); }} Polymorphism (cont) public class Test{ public static void main (String args[]){ Circle C=new Circl1(2.5); Rectangle R=new Rectangle(4.0,5.0); System.out.println( “The shape name is “+C.getName()+ “with Area”+C.getArea(); System.out.println( “The shape name is “+R.getName()+ “with Area”+R.getArea(); } }