/*
 *  TGn01:  Java Before Generics.  In Java versions prior to 1.5 (aka 5.0),
 *  collection classes, such as ArrayList, had to hold plain old Object
 *  references.  Storing references to other kinds of objects isn't a
 *  problem, as the adding of a String to the ArrayList shows.  String
 *  inherits from Object, making String a variety of Object, and ArrayList
 *  is happy to reference any variety of Object.  However, retrieving
 *  the reference is a problem, because we're going in the other direction;
 *  not every Object is a String.  Using type casting, we have to tell Java
 *  how to interpret the reference coming out of the get() method.  Without
 *  the cast, the compiler will flag that assignment as an error.
 *
 *  If you compile this example with a 1.5 (5.0) or later version of Java,
 *  you will get a warning from the compiler that "unchecked or unsafe
 *  operations" are being used.  This illustrates the need for generics:
 *  Without them, the compiler was unable to help the programmer recognize
 *  code that was potentially mixing object references in useless ways.
 *  Now Java can recognize such situations and provide feedback.
 */

import java.io.*;
import java.util.*;

public class TGn01
{
    public static void main (String [] args) 
    {
        ArrayList myList;
        String phrase;
        double value;

        myList = new ArrayList();

        myList.add("Before Generics");    // Place String reference in index 0
        myList.add(new Double(3.14159));  // Place Double reference in index 1

        phrase = (String) myList.get(0);  // Retrieve object reference and cast
        value = ((Double) myList.get(1)).doubleValue();  // Yuck!

        System.out.println(phrase);
        System.out.println(value);
    }
}