Why doesn't String switch statement support a null case?

Question

I am just wondering why the Java 7 switch statement does not support a null case and instead throws NullPointerException? See the comm

Answer 1

Long story short ... (and hopefully interesting enough!!!)

Enum were first introduced in Java1.5 (Sep'2004) and the bug requesting to allow switch on String was filed long back (Oct'95). If you look at the comment posted on that bug at Jun'2004, it says Don't hold your breath. Nothing resembling this is in our plans. Looks like they deferred (ignored) this bug and eventually launched Java 1.5 in the same year in which they introduced 'enum' with ordinal starting at 0 and decided (missed) not to support null for enum. Later in Java1.7 (Jul'2011) they followed (forced) the same philosophy with String (i.e. while generating the bytecode no null check was performed before calling hashcode() method).

So I think it boils down to the fact enum came in first and was implemented with its ordinal begin at 0 due to which they couldn't support null value in switch block and later with String they decided to forced the same philosophy i.e. null value not allowed in switch block.

TL;DR With String they could have take care of NPE (caused by attempt to generate hashcode for null) while implementing java code to byte code conversion but finally decided not to.

Ref: TheBUG, JavaVersionHistory, JavaCodeToByteCode, SO