# of objects, not the size of the objects, determine size of a Collection

Question

There are objects, and references to objects.
Do, List / Set / Map , etc. just maintain a list of 32-bit addresses for their contained objects? What more does a Collection need, memory-wise, to add an element? The size of the objects in a Collection should not matter?
listA.add(new Integer(2));  // listA size grows by 32-bits
listB.add(new GiantSizedClass());  // listB size grows by 32-bitsI started thinking about Collections being able to dynamically grow in runtime. I heard this is complex, but it "looks" like all you do is append a memory address and incriment a counter? This sounds quick, easy, and incorrect. I don't understand. Thanks.

Answer 1

jverd, ejp: you have always been there with quick responses to help me. ejp, i purchased your book "Fundamental Networking in Java". When I start programming again, your book about RMI is on my list. that said.
with all sincerity. i belived that serliazing objects in byte[] allows for storing objects in objects, not object references in objects. here is my test code (just cut/paste):
My idea seems similars to me as cryogenics and so that is the theme of my test code (and it is my favourite movie). note: this code is "proof of concept" and is exetremely hacked together.
public class Test {
  private static HashMap<String, byte[]> barracks = new HashMap<String, byte[]>();
  public static void main(String[] args) {
    try {  new Test().go();  }   catch(Exception e) {  e.printStackTrace();  }
  public void go() throws Exception {
    Employee empl = new Employee("Dallas", "Captain");
    barracks.put(empl.name, cryogenicallyFreeze(empl));
    empl = new Employee("Kane", "Navigator");
    barracks.put(empl.name, cryogenicallyFreeze(empl));
    empl = new Employee("Ripley", "First Officer");
    barracks.put(empl.name, cryogenicallyFreeze(empl));
    empl = new Employee("Ash", "Science Officer");
    barracks.put(empl.name, cryogenicallyFreeze(empl));
    System.out.println("___log file___");System.out.println(".........");
    int id = (int) (System.currentTimeMillis() % barracks.size());
    System.out.println("[Nostromo]: emergency id #"+id+". Re-animation initiated...");
    switch (id) {
      case 0: empl = (Employee) reanimate("Dallas"); break;
      case 1: empl = (Employee) reanimate("Kane"); break;
      case 2: empl = (Employee) reanimate("Ash"); break;
      case 3: empl = (Employee) reanimate("Ripley");
    System.out.println("[Nostromo]: \"" + empl.name + "\" in command.");
    System.out.println("["+empl.name+"]: Hello. I was an object, not a reference, stored in a collection.");
    System.out.println();
    public static Employee reanimate(String name) throws Exception {
        PipedOutputStream pout = new PipedOutputStream();
        PipedInputStream pin = new PipedInputStream(pout);
        byte[] frozenEmpl = (byte[]) barracks.get(name);
        pout.write(frozenEmpl);
        ObjectInputStream ois = new ObjectInputStream(pin);
        return ((Employee) ois.readObject());
    public static byte[] cryogenicallyFreeze(Employee emp) throws Exception {
        PipedOutputStream pout = new PipedOutputStream();
        PipedInputStream pin = new PipedInputStream(pout);
        ObjectOutputStream oos = new ObjectOutputStream(pout);
        oos.writeObject(emp);
        byte[] frozenEmpl = new byte[pin.available()];
        pin.read(frozenEmpl);
        return frozenEmpl;
      public static class Employee implements Serializable {
        String name; String title;
        Employee(String n, String t) {  name = n; title = t;  }
}"inside" of each byte[] object is an "Employee" object? I can't see it any other way. But I am not the sharpest pencil in the drawer...I'm on vacation from coding for a while. maybe i will get it when i start again. thanks.
Edited by: rdkh on Jan 29, 2010 3:53 AM