What is the theme of "After Twenty Years," by O. Henry?

In the story “After Twenty Years” the reader is introduced to the impressive character of the policemen, who loses some of his valor when presented in contrast to the stranger in the door.  The stranger has come to re-acquaint with a friend whom he had agreed to meet twenty years into their future. The stranger is proud of his accomplishments and feels successful.  He wears diamonds to give the reader a sense of his success. He is egotistical in his own self-identity.  When the reader learns that the stranger’s friend is the policeman and the stranger is a crook, the reader must look back at the foreshadowing that took place in the beginning of the story where the policeman was described.  It is here that the theme of “What is a true measure of success.  Who is the more successfulI, the policeman who walks a daily beat but has little money or the criminal with his physical wealth?

Another theme in the story is about human nature and self-conflicts.  The policeman, Jimmy, goes to meet his friend, but soon sees that his friend is wanted for crimes. He is placed in a position where he has to make a moral choice.  He must determine whether to greet his friend or to arrest his friend.  Imagine the inner conflict that the policeman must have felt when he made the decision to have another person arrest his old friend.  Yet, when the reader looks at the character of the policeman as described in the beginning of the story, the reader already sees him of moral character.