Returns a new vector that is a fragment of the specified vector.
The fragment begins at the specified beginIndex and extends to the element
at index endIndex-1.
Thus the length of the fragment is endIndex-beginIndex.
Parameters:
v
beginIndex
endIndex
v.size() is assumed.
null, the returned result is null.
You may call this function in a method-like style:
v.subVector(beginIndex, endIndex)