MutableMap::firstKey
Returns the first key in the current MutableMap
public function firstKey(): ?Tk;
Returns
?Tk- The first key in the currentMutableMap, ornullif theMutableMapis empty.
Returns the first key in the current MutableMap
public function firstKey(): ?Tk;
?Tk - The first key in the current MutableMap, or null if the
MutableMap is empty.