java string类型怎么转化成date类型

Question

String stid=request.getParameter("stid");
String stname=request.getParameter("stname");
String stsex=request.getParameter("stsex");
String stbirthday=request.getParameter("stbirthday");
String clid=request.getParameter("clid");
new StudentManager().insert(new Student(Integer.parseInt(stid), stname, Integer.parseInt(stsex),？？？？, clid));