Question

When overriding equals method for an object can obj below ever be null, if so what are the circumstances?

@Override
 public boolean equals(Object obj) {

Answer 1

Yes, equals() should handle null and in that case it should return false as documented in Object.equals():

For any non-null reference value x, x.equals(null) should return false.

Of course if x is null x.equals(null) won’t return true but it will throw NullPointerException. If you need to compare two possibly null references look at Objects.equals(Object, Object):

Objects.equals(x, x);

The above is always true, even if x == null.