func (l *List) Length() uint {
	l.key.RLock()
	defer l.key.RUnlock()
	return uint(len(l.underlyer))
}
func (l *List) Length() uint {
	l.key.RLock()
	defer l.key.RUnlock()
	return uint(len(l.underlyer))
}
func ( l * List ) Length ( ) uint { l . key . RLock ( ) defer l . key . RUnlock ( ) return uint ( len ( l . underlyer ) ) }
// Length returns the number of elements in the List.
Length returns the number of elements in the List .