两个类Test1.java,staff.javapublic class Test1 {
public static void main(String[] args) {
// TODO Auto-generated method stub
String url = "jdbc:mysql://localhost/test";
String username = "root";
String password = "mysql";
String sql = "select * from staff";
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn=DriverManager.getConnection(url,username,password);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(sql);
Vector<Staff> staffVector = null;
while(rs.next()){
System.out.println(rs.getString(1)+
rs.getString(2)+
rs.getString(3));
Staff st = new Staff();
st.setssid(rs.getString(1));
st.setname(rs.getString(2));
st.setdepartment(rs.getString(3));
staffVector.add(st);
}
rs.close();
conn.close();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}-----------------------------------------------------------------------public class Staff {
private String ssid;
private String name;
private String department;
public void setssid(String ssid){
this.ssid = ssid;
}
public void setname(String name){
this.name = name;
}
public void setdepartment(String department){
this.department = department;
}
public String getssid(){
return ssid;
}
public String getname(){
return name;
}
public String getdeparment(){
return department;
}
}
-----------------------------------------
报错:Exception in thread "main" java.lang.NullPointerException
为什么StaffVector.add(st)会报错呢?
public static void main(String[] args) {
// TODO Auto-generated method stub
String url = "jdbc:mysql://localhost/test";
String username = "root";
String password = "mysql";
String sql = "select * from staff";
try {
Class.forName("com.mysql.jdbc.Driver");
Connection conn=DriverManager.getConnection(url,username,password);
Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery(sql);
Vector<Staff> staffVector = null;
while(rs.next()){
System.out.println(rs.getString(1)+
rs.getString(2)+
rs.getString(3));
Staff st = new Staff();
st.setssid(rs.getString(1));
st.setname(rs.getString(2));
st.setdepartment(rs.getString(3));
staffVector.add(st);
}
rs.close();
conn.close();
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}-----------------------------------------------------------------------public class Staff {
private String ssid;
private String name;
private String department;
public void setssid(String ssid){
this.ssid = ssid;
}
public void setname(String name){
this.name = name;
}
public void setdepartment(String department){
this.department = department;
}
public String getssid(){
return ssid;
}
public String getname(){
return name;
}
public String getdeparment(){
return department;
}
}
-----------------------------------------
报错:Exception in thread "main" java.lang.NullPointerException
为什么StaffVector.add(st)会报错呢?
应该这样Vector<Staff> staffVector = new Vector<Staff>();