Now I would like to present you a little characterisation of Jamie:

Jamit is a 16-years old boy, who lives in Ashingford. His hobby is to play squash and he does it very well. Jamie's best friend is Spider, who's living next to him. Spider isn't accepted by Jamie's father, because he isn't a sports guy.
One of the best characteristics of jamie is that he takes care of the people, he likes, He tries to take care of his mother particularly when she was treated badly by her husband. Ofthen she's down and at those moments, jamie tries to help her out of this.
Ia addition he rescued Abby when she was in the bad situation in were the two men pursued her hardly.
Jamie didn't think at himself in this moment and he gets angry with the two men only to help Abby.
But on the oter side, Jamie is a bit weak. In his opinion, there's no chance to be treated better by his father, so he let him easily do waht he wants instead of doing some resistance.
In the end of the book, Abby gave him back his self-confidence and so Jamie went back to his father without having fear.
In my opinion, Jamie can be a good friend to people, who are not violence.