Are two Java objects with same hashcodes not necessarily equal?

Question

I understand why providing same hashcode for two equal (through equals) objects is important. But is the vice versa true as well, if two objects have same hash

Answer 1

Curiously, NumberFormat is an example of a Java foundation class which violates the recommendation that:

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects.

Here is some code showing this, at least under the version of Java I'm currently running under Mac OS X 10.6.

Numberformat nf = NumberFormat.getNumberInstance();
NumberFormat nf2 = NumberFormat.getNumberInstance();
assert nf != nf2;  // passes -- they are different objects
assert !nf.equals(nf2);  // passes -- they are not equal
assert nf.hashCode() != nf2.hashCode();  // fails -- same hash code