In the contender why does the police man stop Alfred?

In "The Contender" by Robert Lipsyte, the policeman stops Alfred because he is suspicious of him and his friends, who are hanging around in a neighborhood known for trouble. The officer questions Alfred to assert authority and to check on his intentions, reflecting the challenges and scrutiny that young Black men often face in urban environments. This interaction highlights the themes of societal judgment and the struggle for respect in the face of adversity.