分享程序员开发的那些事...
更新时间：2022-10-23 22:21:10
大家好，
i'我正在使用以下代码，并且我在线程main中获得了
异常java.lang.nullpointerexception在粗体的行。帮我解决这个问题
import java.applet。*;
import java.awt。*;
import java .io。*;
import javax.swing。*;
import java.sql。*;
import java.awt.event。 *;
import sun.jdbc.odbc。*;
public class Customerdetails extends Frame implements ActionListener
{
TextField ccod，cname，add，phno，conp，email，fax;
标签l1，l2，l3，l4，l5，l6，l7;
按钮保存，退出;
连接con;
ResultSet rs;
语句stmt;
String s1， s2，s3，s4，s5，s6，s7;
public Customerdetails（）
{
super（" CustomerDetails" ;）;
setSize（800,800）;
setLayout（new GridLayout（7,2,45,45））;
l1 = new标签（客户代码）;
l2 =新标签（CompanyName）;
l3 =新标签（地址）;
l4 =新标签（PhoneNumber）;
l5 =新标签（联系人）;
l6 =新标签（" EmailAddress"）;
l7 =新标签（FaxNumber）;
add（l1）;
add（ ccod）;
add（l2）;
add（cname）;
add（l3）;
添加（添加）;
add（l4）;
add（phno）;
add（l5）;
add（conp）;
add（l6）;
add（email）;
add（l7）;
add（传真）;
save.addActionListener（this）;
exit.addActionListener（this）;
setVisible（true）;
addWindowListener（new WindowAdapter（）{
public void WindowClosing（WindowEvent w）{System .exit（0）;}}）;
}
public void actionPerformed（ActionEvent ae）
{
>
if（ae.getSource（）== save）
{
s1 = ccod.getText（） ;
s2 = cname.getText（）;
s3 = add.getText（）;
s4 = phno.getText（）;
s5 = conp.getText（）;
s6 = email.getText（）;
s7 = fax.getText（）;
尝试
{
String query =" insert into Customerdetails（Customercode，CompanyName，Address，PhoneNumber，Cont act person，EmailAddress， FaxNumber）" +
" values（''" + s1 +"''，''" + s2 +'''，''" + s3 +" ''，''" + s4 +"''，''" + s5 +"''，''" + s6 +"''，''" + s7 +"''） " ;;
Class.forName（" sun.jdbc.odbc.JdbcOdbcDriver"）;
con = DriverManager.getConnection（" jdbc：odbc：prism"） ;
stmt = con.createStatement（）;
rs = stmt.executeQuery（query）;
stmt.close（）;
}
catch（ClassNotFoundException e）
{
System.out.println（e）;
}
catch（SQLException e）
{
系统。 out.println（e）;
}
}
if（ae.getSource（）==退出）
{
System.exit（0）;
}
}
public static void main（String args []）
{
Customerdetails cd = new Customerdetails（）;
}
}
1.）发布代码时使用代码标签。
2.）构造函数取消引用未初始化的变量。比如看按钮。
Hi pradeep84，
欢迎来到TSDN！
你知道为什么这样吗发生了吗？
看看这个例子。展开 | 选择 | Wrap | 行号
谢谢先生..，
即使我声明了..它显示了相同的错误.. plz我说的确切地说我要宣告.......并且在wat类型......hi all,
i''m using the following code and i''m getting
exception in thread "main" java.lang.nullpointerexception at the line which is in bold. help me to solve this problem
import java.applet.*;
import java.awt.*;
import java.io.*;
import javax.swing.*;
import java.sql.*;
import java.awt.event.*;
import sun.jdbc.odbc.*;
public class Customerdetails extends Frame implements ActionListener
{
TextField ccod,cname,add,phno,conp,email,fax;
Label l1,l2,l3,l4,l5,l6,l7;
Button save,exit;
Connection con;
ResultSet rs;
Statement stmt;
String s1,s2,s3,s4,s5,s6,s7;
public Customerdetails()
{
super("CustomerDetails");
setSize(800,800);
setLayout(new GridLayout(7,2,45,45));
l1=new Label("Customercode");
l2=new Label("CompanyName");
l3=new Label("Address");
l4=new Label("PhoneNumber");
l5=new Label("Contact person");
l6=new Label("EmailAddress");
l7=new Label("FaxNumber");
add(l1);
add(ccod);
add(l2);
add(cname);
add(l3);
add(add);
add(l4);
add(phno);
add(l5);
add(conp);
add(l6);
add(email);
add(l7);
add(fax);
save.addActionListener(this);
exit.addActionListener(this);
setVisible(true);
addWindowListener(new WindowAdapter(){
public void WindowClosing(WindowEvent w) {System.exit(0);}});
}
public void actionPerformed(ActionEvent ae)
{
if(ae.getSource()==save)
{
s1=ccod.getText();
s2=cname.getText();
s3=add.getText();
s4=phno.getText();
s5=conp.getText();
s6=email.getText();
s7=fax.getText();
try
{
String query = "insert into Customerdetails (Customercode,CompanyName,Address,PhoneNumber,Cont act person,EmailAddress,FaxNumber)"+
"values(''"+s1+"'',''"+s2+"'',''"+s3+"'',''"+s4+"'',''"+s5+ "'',''"+s6+"'',''"+s7+"'')";
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:prism") ;
stmt=con.createStatement();
rs=stmt.executeQuery(query);
stmt.close();
}
catch(ClassNotFoundException e)
{
System.out.println(e);
}
catch(SQLException e)
{
System.out.println(e);
}
}
if(ae.getSource()==exit)
{
System.exit(0);
}
}
public static void main(String args[])
{
Customerdetails cd=new Customerdetails();
}
}hi all,
i''m using the following code and i''m getting
exception in thread "main" java.lang.nullpointerexception at the line which is in bold. help me to solve this problem
import java.applet.*;
import java.awt.*;
import java.io.*;
import javax.swing.*;
import java.sql.*;
import java.awt.event.*;
import sun.jdbc.odbc.*;
public class Customerdetails extends Frame implements ActionListener
{
TextField ccod,cname,add,phno,conp,email,fax;
Label l1,l2,l3,l4,l5,l6,l7;
Button save,exit;
Connection con;
ResultSet rs;
Statement stmt;
String s1,s2,s3,s4,s5,s6,s7;
public Customerdetails()
{
super("CustomerDetails");
setSize(800,800);
setLayout(new GridLayout(7,2,45,45));
l1=new Label("Customercode");
l2=new Label("CompanyName");
l3=new Label("Address");
l4=new Label("PhoneNumber");
l5=new Label("Contact person");
l6=new Label("EmailAddress");
l7=new Label("FaxNumber");
add(l1);
add(ccod);
add(l2);
add(cname);
add(l3);
add(add);
add(l4);
add(phno);
add(l5);
add(conp);
add(l6);
add(email);
add(l7);
add(fax);
save.addActionListener(this);
exit.addActionListener(this);
setVisible(true);
addWindowListener(new WindowAdapter(){
public void WindowClosing(WindowEvent w) {System.exit(0);}});
}
public void actionPerformed(ActionEvent ae)
{
if(ae.getSource()==save)
{
s1=ccod.getText();
s2=cname.getText();
s3=add.getText();
s4=phno.getText();
s5=conp.getText();
s6=email.getText();
s7=fax.getText();
try
{
String query = "insert into Customerdetails (Customercode,CompanyName,Address,PhoneNumber,Cont act person,EmailAddress,FaxNumber)"+
"values(''"+s1+"'',''"+s2+"'',''"+s3+"'',''"+s4+"'',''"+s5+ "'',''"+s6+"'',''"+s7+"'')";
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
con=DriverManager.getConnection("jdbc:odbc:prism") ;
stmt=con.createStatement();
rs=stmt.executeQuery(query);
stmt.close();
}
catch(ClassNotFoundException e)
{
System.out.println(e);
}
catch(SQLException e)
{
System.out.println(e);
}
}
if(ae.getSource()==exit)
{
System.exit(0);
}
}
public static void main(String args[])
{
Customerdetails cd=new Customerdetails();
}
}1.) Use code tags when posting code.
2.) Your constructor dereferences variables that are not initialized. See the buttons for example.
Hi pradeep84,
Welcome to TSDN!
Do you know why does this happen?
Have a look at this example.Expand|Select|Wrap|Line Numbers
Thank you sir..,
Even though i declared.. it shows the same error.. plz say me exactly where i hav to declare....... and in wat type...