Does a police officer who approaches an individual on the street or in another public place violate the Fourth Amendment by asking him if he is willing to answer some questions?

"[L]aw enforcement officers do not violate the Fourth Amendment by merely approaching an individual on the street or in another public place, by asking him if he is willing to answer some questions, by putting questions to him if the person is willing to listen, or by offering in evidence in a criminal prosecution his voluntary answers to such questions. [Citations.] Nor would the fact that the officer identifies himself as a police officer, without more, convert the encounter into a seizure requiring some level of objective justification. [Citation.] The person approached, however, need not answer any question put to him; indeed, he may decline to listen to the questions at all and may go on his way. [Citation.] He may not be detained even momentarily without reasonable, objective grounds for doing so; and his refusal to listen or answer does not, without more, furnish those grounds. [Citation.]" (Florida v. Royer (1983) 460 U.S. 491, 497-498.)