Object lifetime

Question

How come if I make an object, put it into an array or Collection,
then set the object's reference to null, the object stays in the collection?
In other words, why does this print the colors of the two Beads I have set to null?public class Bead{
  static Bead[] necklace;
  String color;
  public void setColor(String col){
    color=col;
  public String getColor(){
    return color;
  public static void main(String[] args){
    necklace = new Bead[2];
    Bead b1 = new Bead();
    b1.setColor("red");
    necklace[0] = b1;
    b1=null;
    b1 = new Bead();
    b1.setColor("blue");
    necklace[1] = b1;
    b1=null;
    for(int i=0;i<necklace.length;i++){
      System.out.println(necklace.getColor()+"\n");
}prints:
red
blue
If instead of setting the reference variable to null, I change the color, this does show up in the object in the collection public class Bead{
  static Bead[] necklace;
  String color;
  public void setColor(String col){
    color=col;
  public String getColor(){
    return color;
  public static void main(String[] args){
    necklace = new Bead[2];
    Bead b1 = new Bead();
    b1.setColor("red");
    necklace[0] = b1;
    b1.setColor("yellow");
    b1 = new Bead();
    b1.setColor("blue");
    necklace[1] = b1;
    for(int i=0;i<necklace.length;i++){
      System.out.println(necklace.getColor()+"\n");
}prints:
yellow
blue

Answer 1

    Bead b1 = new Bead();
    b1.setColor("red");
    necklace[0] = b1;b1 is a reference to a Bead object. necklace[0] is another reference to that same Bead object. The Bead object has two references.    b1=null;b1 no longer references the Bead object, necklace[0] still references it. The Bead object has one reference.    b1 = new Bead();
    b1.setColor("blue");
    necklace[1] = b1;b1 is a reference to a new and different Bead object. necklace[1] is another reference to that same new and different Bead object. The new and different Bead object has two references.    b1=null;b1 no longer references the new and different Bead object, necklace[1] still references it. The new and different Bead object has one reference.