String num = (string) request.getParameter("num");报错

编写String num = (string) request.getParameter("num");时，报错
Multiple annotations found at this line:
- string cannot be resolved to
a type
- string cannot be resolved to
a type
- string cannot be resolved to
a type
但是我的jre没有×，该怎么办

String num = (String) request.getParameter("num");
String不是string