Não encontrei o syncronized no add da Vector...
Open Declaration boolean java.util.Vector.add(String e)
add
public boolean add(E e)
Appends the specified element to the end of this Vector.
Specified by:
add in interface Collection<E>
Specified by:
add in interface List<E>
Overrides:
add in class AbstractList<E>
Parameters:
e - element to be appended to this Vector
Returns:
true (as specified by Collection.add(E))
Since:
1.2