public synchronized boolean addAll(Collection<? extends E> c){
  modCount++;
  Object[] a=c.toArray();
  int numNew=a.length;
  ensureCapacityHelper(elementCount + numNew);
  System.arraycopy(a,0,elementData,elementCount,numNew);
  elementCount+=numNew;
  return numNew != 0;
}

public synchronized boolean addAll ( Collection < ? extends E > c ) { modCount ++ ; Object [ ] a = c . toArray ( ) ; int numNew = a . length ; ensureCapacityHelper ( elementCount + numNew ) ; System . arraycopy ( a , 0 , elementData , elementCount , numNew ) ; elementCount += numNew ; return numNew != 0 ; }
appends all of the elements in the specified collection to the end of this vector , in the order that they are returned by the specified collection ' s iterator . the behavior of this operation is undefined if the specified collection is modified while the operation is in progress . ( this implies that the behavior of this call is undefined if the specified collection is this vector , and this vector is nonempty . )
