Amazing: Vector can have elements of different types!!!

Hi,

I just realized/found that in Java, Vector can have elements with
different types. I guess other collections are the same. See my code
below. I don't know Generics from Java 5.0. But I am really amazed that
heterogenous types of data can be put in the same place(Vector).

I have a couple questions:
(1)Is that common that people utilize this feature (putting different
types of data in one place)?
(2)Is there a way to find out what type of each element belongs to? (say
I forgot 1st element is Person, 2nd element is String, etc)

Thank you very much.

=============TestDemo.java============
import java.util.*;

public class TestDemo {
    public static void main(String[] args)
    {
        Vector myVec = new Vector();
        Person aPerson = new Person("Tom");
        String aString = "Hello World";
        int[] intArray = {3, 5, 9};

        myVec.addElement(aPerson);
        myVec.addElement(aString);
        myVec.addElement(intArray);

        Person newPerson = (Person)myVec.elementAt(0);
        System.out.println("Here is the person:" + newPerson.getName());
//print Tom

        String newString = (String)myVec.elementAt(1);
        System.out.println("Here is the string:" + newString); //print Hello
World

        int[] newArray = (int[])myVec.elementAt(2);
        System.out.println("Here is the array element: " + newArray[1]);
//print 5
    }
}

==============Person.java================
public class Person {
    private String sName;

    public Person()
    {
        //empty
    }

    public Person(String s)
    {
        this.sName = s;
    }

    public String getName()
    {
        return sName;
    }
}