Example Programs for Java Abstract Classes
Abstract Classes in Java
import java.util.*;
/**
* This program demonstrates abstract classes.
*/
public class PersonTest
{
public static void main(String[] args)
{
Person[] people = new Person[2];
// fill the people array with Student and Employee objects
people[0] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
people[1] = new Student("Maria Morris", "computer science");
// print out names and descriptions of all Person objects
for (Person p : people)
System.out.println(p.getName() + ", " + p.getDescription());
}
}
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);
}
public void raiseSalary(double byPercent)
{
double raise = salary * byPercent / 100;
salary += raise;
}
private double salary;
private Date hireDay;
}
class Student extends Person
{
/**
* @param n the student's name
* @param m the student's major
*/
public Student(String n, String m)
{
// pass n to superclass constructor
super(n);
major = m;
}
public String getDescription()
{
return "a student majoring in " + major;
}
private String major;
}
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