Computer Science 225
Advanced Programming

Spring 2017, Siena College

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AbstractClass BlueJ Project

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AbstractClass Source Code

The Java source code for AbstractClass is below. Click on a file name to download it.

AbstractClass.java

/*
 * Example AbstractClass: demonstrating an abstract class
 *
 * Jim Teresco, Siena College, Computer Science 225, Spring 2017
 *
 * Based heavily on example from Darren Lim
 */

import java.util.ArrayList;

/* The method is declared as abstract to indicate that it will include
 * one or more abstract methods.
 */
abstract class Student
{
    protected String name = "Fred";
    
    /* any class that extends Student will be required to implement this method */
    protected abstract void getName();
    
    /* and we'll provide a method everyone will inherit also */
    public void setName(String newName) {
        
        name = newName;
    }
        
}


class Undergraduate extends Student
{
    @Override
    protected void getName()
    {
        System.out.println("Undergraduate : " + name);
    }
} 

class Freshman extends Undergraduate
{
}

class Graduate extends Student
{
    @Override
    protected void getName()
    {
        System.out.println("Graduate : " + name);
    }

}

class Phd extends Graduate
{
    @Override
    protected void getName()
    {
        System.out.println("Phd : " + name);
    }
}

public class AbstractClass
{

    public static void main(String[] args) 
    {
        // populate an ArrayList with Student objects and instances of derived classes
        ArrayList<Student> students = new ArrayList<>();
        // this will not be allowed, since we cannot instantiate an abstract class
        //students.add(new Student());
        students.add(new Undergraduate());
        students.add(new Freshman());
        students.add(new Graduate());
        students.add(new Phd());
        
        // any Student object can call setName
        students.get(0).setName("Mary");
        students.get(1).setName("Don");
        students.get(2).setName("Alice");
        
        // let's call each one's getName method, which each Student is
        // guaranteed to have, even though class Student doesn't provide one.
        for (Student s : students) {
            
            s.getName();
        }
    
    }
}