Step-by-step explanation:
According to Bob, his friend Jimmy Wells was twenty years old when he last saw him twenty years ago. Now Jimmy would be forty. The years between twenty and forty are the most crucial years in a man's life. Whatever he has become by the age of forty is what he will remain. Jimmy would be a middle-aged policeman, probably a little overweight, probably married and having a home and children. He was barely out of his teens when he and Bob parted twenty years ago. Jimmy may have joined the police force shortly afterwards. Bob describes him at the age of twenty as a "plodding" type of person. The police force could have appealed to him because it provided security and respectability. He has gained a lot of practical experience on the job. We can see that in the adroit way he handles Bob, never letting him know that he in fact is Jimmy Wells and is keeping their appointment. O. Henry does not introduce Jimmy by name at the beginning of the story, but the author describes the manner and actions of a typical New York beat cop to let the reader see that this is a man who has become completely shaped into the role of an honest, responsible police officer who likes his routine job. The way Jimmy twirls his club represents years of walking his beat and passing the time by practising his club-twirling.
THE POLICEMAN ON the beat moved up the avenue impressively. The impressiveness was habitual and not for show, for spectators were few...Trying doors as he went, twirling his club with many intricate and artful movements, turning now and then to cast his watchful eye adown the pacific thoroughfare, the officer, with his stalwart form and slight swagger, made a fine picture of a guardian of the peace.
Jimmy has been shaped by what he does. This happens to most men with increasing age. Bob, too, has been shaped by what he does. Bob has been shaped into a stereotypical petty criminal who has been on the run for twenty years and is superficially successful but has missed out on all the things that Jimmy has acquired, including a home and a family, friends, security, comfort, roots, and a certain degree of authority. O. Henry's story is mainly intended to show the contrast between the two men after twenty years. Both of them made career choices twenty years ago, and both have become what they are as a result of their choices. Bob brags to the policeman, whom he doesn't recognize, about having been successful. He doesn't expect Jimmy to have done as well. But who is the really successful man?