if someone behaves over familiar with you, when you don't know them

how should you react?

today i was in the locker rooms in the swimming baths, and i was drying myself and getting dressed, ready to leave, when this man comes near me whistling his head off? he couldn't stop whistling...and i took it as he was being over familiar with me...and i felt angry, because i don't know him, so why is he acting familiar?

i get this sometimes from strangers in the area i live in, i interpret what they do as being too familiar...whether it be someones coughing a lot near me or just looking at me...i see it as acting too familiar with me, when i don't know them and are a stranger to them.

how should i deal with it?