怎么解决The method getIdcard() is undefined for the type String

如何解决The method getIdcard() is undefined for the type String
这事封装对象的代码
package cn.itcast.domain;

public class Student {

private String idcard;
private String examid;
private String name;
private String location;
private double grade;


public String getIdcard() {
return idcard;
}
public void setIdcard(String idcard) {
this.idcard = idcard;
}
public String getExamid() {
return examid;
}
public void setExamid(String examid) {
this.examid = examid;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getLocation() {
return location;
}
public void setLocation(String location) {
this.location = location;
}
public double getGrade() {
return grade;
}
public void setGrade(double grade) {
this.grade = grade;
}

}
这事操作代码
import cn.itcast.utils.XmlUtils;

public class StudentDao {


public void add(String s){

try {
Document document = XmlUtils.getDocument();

//创建封装学生信息的标签
Element student_tag = document.createElement("student");
student_tag.setAttribute("idcard", s.getIdcard());
student_tag.setAttribute("examid", s.getExamid());

} catch (Exception e) {
throw new RuntimeException(e);
}

}
}
这里的getIdcard()和getExamid（）方法会出现The method getIdcard() is undefined for the type String的错误啊！

[解决办法]
将StudentDao改成下面的代码应该就OK了，你试试

Java code

import cn.itcast.utils.XmlUtils;public class StudentDao {    public void add(Student s){        try {            Document document = XmlUtils.getDocument();//创建封装学生信息的标签            Element student_tag = document.createElement("student");            student_tag.setAttribute("idcard", s.getIdcard());            student_tag.setAttribute("examid", s.getExamid());        } catch (Exception e) {            throw new RuntimeException(e);        }    }}