She told the Richard and Judy show that she had long known how the series would end, because she had written the last chapter "in something like 1990".
Rowling said she could understand why authors might want to finish off their main characters in order to ensure they could never be resurrected, according to the BBS News.
She would not say if this would be the case with Harry.
The author added: "I don't think I'm ever going to have anything like Harry again. You just get one like Harry."
Ms Rowling said she still writes in cafes and based the character of Hermione on a combination of herself and her sister when they were young, ITV.com reports.