why , if the insertion point of a search is at element 2, the actual insertion point returned will be -3?
<p>i did not understand this point in in <code>Collection</code> 
"Unsuccessful searches return an int index that represents the insertion point.
The insertion point is the place in the collection/array where the element
would be inserted to keep the collection/array properly sorted. Because positive return values and 0 indicate successful searches, the <code>binarySearch()</code>
method uses negative numbers to indicate insertion points. Since <strong>0 is a valid
result for a successful search, the first available insertion point is -1. Therefore,
the actual insertion point is represented as (-(insertion point) -1). For
instance, if the insertion point of a search is at element 2, the actual insertion
point returned will be -3.</strong>"</p>
