Proposal: Elvis and Other Null-Safe Operators

[Winson Quock]

Hi,

I would like to add one small addition to this proposal, if it is not too
late.

Null-safe for-each loop:

List<String> strings = null; // could be null
for (String s : string) { // if list or array is null, do not throw NPE but
skip the loop
 ...
}

ADVANTAGE:

This replace the current cumbersome and often forgot checks

if (string != null) {
  for (String s : string) { // if list or array is null, do not throw NPE
but skip the loop
    ...
  }
}

COMPATIBILITY: This is generally backward compatibility except perhaps some
very arcane codes depending on the throwing of NPE to function correctly,
like

int totalLen = 0;
try {
  for (String s : string) { // if list or array is null, do not throw NPE
but skip the loop
    totalLen += s.length();
  }
} catch (NullPointerException e) {
  totalLength = -1;
}

Such practices should be exceeding rare and should not be a concern, or we
can introduce a -X compiler option to restore the original behavior.

ALTERNATIVE: Use a new '?:' operator for null-safe loop, similar to those
other operators proposed by this proposal

for (String s ?: string) { // if list or array is null, do not throw NPE but
skip the loop
 ...
}

This alleviates the compatibility issue with the arcane case above.