I have to wonder if Jonathan became king what kind of king he would have made. There is a lot of David in Jonathan, or could be that there is a lot of Jonathan in David. Jonathan was apparently loved by the people. His confidence was in God and loyal to his father. I believe that he would have been a good king, one that followed God. However, he was the son of Saul - God did not establish Saul's kingdom so it seems that Jonathan was a victim of his father's disobedience.
We also see here in this chapter how important it is to keep your oath. Saul was willing to kill his own son to keep the oath and keep whole with God so as not to incur God's wrath because of disobedience to the oath. Once again we are reminded to think twice about making oaths and promises. Do not make an oath or be rash about making them. Have you made an oath? Do you remember them?