Thread: Stuck, looking for input

Hi, guys-

I'm having a bit of trouble with the my ArrayList. Basically, what I need to do is put in four persons (a class I developed along with Student and Instructor) into an ArrayList for a homework assignment. Then, using a simple loop I need to take it out and get the names. For some reason, "Dr. Tabatt" shows up as being in all four indexes... why is this? What am I doing wrong?

import java.util.ArrayList;
 
public class PeopleApp {
 
	public static void main(String[] args) {
 
		Person p1 = new Person("Bobby", 1988);
		Student p2 = new Student("Sammy", 1987, "Psychology");
		Student p3 = new Student("Ronnie", 1990, "Religious Studies");
		Instructor p4 = new Instructor("Dr. Tabatt", 1928, 100000);
		Person x;
 
		ArrayList<Person> People;
		People = new ArrayList<Person>();
 
		People.add(0, p1);
		People.add(1, p2);
		People.add(2, p3);
		People.add(3, p4);
 
		for (int i = 0; i < 4; i++) {
			x = People.get(i);
			System.out.println(x.getName());
		}
 
	}
}

Let me know if you need the Person, Student and Instructor code... getName() is supposed to return the name of the Person/Student/Instructor.

-Thanks in advance

The code to the other classes may be helpful...is the variable that stores the name in these classes by any chance static?

Arraylists have the nifty feature of working like a stack, you dont have to specify an index if you just want the next piece to fall on top of the stack. I've had tons of issues working with arraylists where I try to sort them before theyre full/when theyre empty and it always (ALWAYS) messes things up.

Could you swap this for:

People.add(p1);
People.add(p2);
People.add(p3);
People.add(p4);

Just to see what happens, havent got the other classes so I cant try it out for myself .