java中的try catch语句没有执行while直接跳出去了

public static List findBySex(Student stu){
String sql=String.format("select * from student where sex='%s'",stu.getSex());
List students =new ArrayList();
try {
ResultSet rs=MyDbHelper.executeQuery(sql);
while (rs.next()) //运行到这里就直接跳出去了
{
Integer id=rs.getInt(rs.findColumn("id"));
String name=rs.getString(rs.findColumn("name"));
String sex=rs.getString(rs.findColumn("sex"));
Student student=new Student();
student.setId(id);
student.setName(name);
student.setSex(sex);
students.add(student);
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

rs返回空？建议先校验非空，即改成while(rs != null && rs.next()）