Inheritence query??

[Rohit chandra]

    
import java.text.*;
import java.util.*;
 
public class PersonTest
{
public static void main(String[] args)
{
Person[] people = new Person[2];
 
people[0]=new Employee("Harry", 50000,1980,10,1);
people[1]=new Student("Maria","Computer Science");


for(Person p: people)
System.out.println(p.getName() + ", " + p.getDescription());
 
//System.out.println(people[0].getSalary());// here goes the problem

}
}
 
abstract class Person
{
public Person(String n)
{
name=n;
}
 
public abstract String getDescription();
 
public String getName()
{
return name;
}
 
private String name;
}
 
class Employee extends Person
{
public Employee(String n,double s,int year,int month,int day)
{
super(n);
salary=s;
GregorianCalendar calendar = new GregorianCalendar(year,month-1,day);
hireDay = calendar.getTime();
}
 
public double getSalary()
{
return salary;
}
 
public Date getHireDay()
{
return hireDay;

}
 
public String getDescription()
{
 return String.format("AN Employee with a salary of $%.2f",salary);
}

private double salary;
private Date hireDay;
}
 
class Student extends Person
{
public Student(String n,String m)
{
super(n);
major=m;
}
 
public String getDescription()
{
return " A student majoring in " +major;
}

private String major;
}

The program was working fine unless i entered System.out.println(people[0].getSalary());
I have no idea why the compiler is flagging this as error??
1. The object reference has an access to the getDescription() method of class Employee byt whenever i try to access getSalary() method on the same object reference it flags an error??

[Saathvik Reddy]

Could you paste your error?
[ July 18, 2007: Message edited by: Sheethal Reddy ]

[Garrett Rowe]

There is no getSalary() in Person class. In order to call getSalary() you'll have to downcast to an Employee.

System.out.println(((Employee)people[0]).getSalary());

[Rohit chandra]

@above
Person is an abstract class, however the object variable of Person is pointing to Employee object. If object variable of Person can access getDescription() method in Employee class then why not getSalary() method.

[Rohit chandra]

Error is:

javac PersonTest.java
PersoTest.java:19:cannot find symbol
symbol: method getSalary()
location: class Person
System.out.println(people[0].getSalary());
^

[Garrett Rowe]

If object variable of Person can access getDescription() method in Employee class then why not getSalary() method.

Because getDescription() is declared in Person class, getSalary() is not. If you are using a reference of type Person, you may only call methods visible in Person class (and any class it inherits from) unless you cast the reference to a more specific type.
[ July 18, 2007: Message edited by: Garrett Rowe ]

[Ernest Friedman-Hill]

Originally posted by Rohit chandra:
@above
Person is an abstract class, however the object variable of Person is pointing to Employee object. If object variable of Person can access getDescription() method in Employee class then why not getSalary() method.

Because getDescription() is defined for Person, whereas getSalary() is not. The fact that Person.getDescription() is abstract doesn't matter; the compiler knows that any object of type Person has this method.

If you use a cast, as suggested above, then you're telling the compiler that the Person is really an Employee, so then it can find the getSalary() method.