Java object comparison and Hashtable with Object keys
MyObject x = new MyObject();
MyObject y = x;

Integer x = new Integer(1);
Integer y = new Integer(1);
System.out.println(x == y); // False
System.out.println(x.equals(y)); // True

Object o = new Object();

List<Object> l1 = new ArrayList<Object>();
List<Object> l2 = new ArrayList<Object>();

l1.add(o);
l2.add(o);

Object o1 = l1.get(0);
Object o2 = l2.get(0);

System.out.println(o1 == o2); // prints true

String s = "hello";
List<String> l = new ArrayList<String>();
l.add(s);
s = "world";
System.out.println(l.get(0));  // prints hello