Problem about "Exception in thread "main" java.lang.NullPointerException"
This is t error message once i run the file
Exception in thread "main" java.lang.NullPointerException
at sendInterface.<init>(sendInterface.java:64)
at sendInterface.main(sendInterface.java:133)
* @(#)sendInterface.java
* @author
* @version 1.00 2008/7/18
import java.awt.BorderLayout;
import java.awt.Image;
import java.awt.GridLayout;
import java.awt.Panel;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.DefaultListModel;
import javax.swing.Icon;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JList;
import javax.swing.JRadioButton;
import javax.swing.JScrollPane;
import javax.swing.ListModel;
import javax.swing.UIManager;
import javax.swing.SwingConstants;
import java.io.*;
import java.sql.*;
import java.net.*;
public class sendInterface /*implements ActionListener*/{
JFrame frame = new JFrame();
private Panel topPanel;
private Panel sendMessagePanel;
private Panel sendFilePanel;
private JLabel senderID;
private JLabel receiverID;
private JLabel senderDisplay;
private DefaultListModel receiverListModel = new DefaultListModel();
private JList receiverID_lst = new JList(receiverListModel);
private JRadioButton sendType;
String userName;
String[] userList = null ;
int i=0;
Connection con;
public sendInterface() {
String ListName;
try
JFrame.setDefaultLookAndFeelDecorated( true );
catch (Exception e)
System.err.println( "Look and feel not set." );
frame.setTitle( "Send Interface" );
topPanel.setLayout( new GridLayout( 2 , 1 ) ); //line 64*************************
senderID = new JLabel( "Sender:", SwingConstants.LEFT );
senderDisplay = new JLabel( "'+...+'", SwingConstants.LEFT );
receiverID = new JLabel( "Receiver:", SwingConstants.LEFT);
// receiverID_lst = new JList( ListName );
frame.add(senderID);
frame.add(senderDisplay);
frame.add(receiverID);
// frame.add(receiverListModel);
frame.add(new JScrollPane(receiverID_lst), BorderLayout.CENTER);
frame.setLocation(200, 200);
frame.setSize(250, 90);
frame.setVisible(true);
public void setListName(String user)
try{
userName = user;
Class.forName("com.mysql.jdbc.Driver");
String url = "jdbc:mysql://localhost:3306/thesis";
con = DriverManager.getConnection(url, "root", "");
Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_READ_ONLY);
ResultSet rs = stmt.executeQuery("select * from user where User_ID!= '" + userName + "'");
System.out.println("Display all results:");
while(rs.next()){
String user_id = rs.getString("User_ID");
System.out.println("\tuser_id= " + user_id );
// receiverListModel.addElement(user_id);
userList=user_id;
i++;
}//end while loop
receiverListModel.addElement(userList);
catch(Exception ex)
ex.printStackTrace();
finally
if (con != null)
try
con.close ();
System.out.println ("Database connection terminated");
catch (Exception e) { /* ignore close errors */ }
public String getUserName()
return userName;
public String[] getUserList()
return userList;
public static void main(String[] args) {
new sendInterface(); //line 133******************************************
thank ur reply:D
Edited by: ocibala on Aug 3, 2008 9:54 AM
And where do you instantiate topPanel before you invoke setLayout?
db
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the variable state is assigned to test1. This variable(test1) is not initialized anywhere.It is initialized in the c'tor. Which is invoked after the "global" object and attribute initialization. So it is there, but comes too late.
You should definitly not write a technical Java blog and post it all over the place. -
Exception in thread "main" java.lang.NullPointerException error JDeveloper 12c
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I am getting error "Exception in thread "main" java.lang.NullPointerException. I have no idea what have I been doing wrong.
Maybe you haven't read it yet but I told you in your other thread what you were doing wrong and, step by step, how to address the problem.
https://forums.oracle.com/thread/2611124
I'm not going to repeat everything again just this one main piece of advice:
Until you get you code working outside the database don't even bother trying to load it into the DB and create a Java stored procedure.
You are trying to deal with too many different issues at the same time. Unless you solve your primary Java problem by fixing the code outside the DB you will have nothing but problems loading it into the DB.
And just get rid of this line of code - you don't need it anymore and it hasn't been done like that for many years now:
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Exception in thread "main" java.lang.NullPointerException
hi
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System.out.println(" Parts being set" );Thank you for your reply. I think i used
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<code>
import java.util.*;
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Hi
I am getting the following error. I cannot see any uninitialised objects. I have spent enough time on it .Could someone help me with this.
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Exception in thread "main" java.lang.NullPointerException
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at pointlist.pointList.add(pointList.java:31)
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package pointlist;
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// System.out.println(cityArray[i].getLengthAroundB());
// System.out.println(cityArray[i].getSpeedAB());
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/* for(int i=0; i<cityArray.length ;i++)
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sortedCityArray[j+1]=new City(cityArray[i].getCity(),cityArray[i].getNextCity(),cityArray[i].getLengthAB(),cityArray[i].getLengthAroundB(),cityArray[i].getSpeedAB());
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for(int i=0; i<cityArray.length ;i++)
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for(int i=0; i<cityArray.length ;i++)
if(sortedCityArray[j].getNextCity().equals(cityArray[i].getCity())){
sortedCityArray[j+1]=new City(cityArray[i].getCity(),cityArray[i].getNextCity(),cityArray[i].getLengthAB(),cityArray[i].getLengthAroundB(),cityArray[i].getSpeedAB());
break;
// j++;
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System.out.println(sortedCityArray[0].getNextCity());
System.out.println(sortedCityArray[0].getLengthAB());
System.out.println(sortedCityArray[0].getLengthAroundB());
System.out.println(sortedCityArray[0].getSpeedAB());
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System.out.println(sortedCityArray[1].getLengthAB());
System.out.println(sortedCityArray[1].getLengthAroundB());
System.out.println(sortedCityArray[1].getSpeedAB());
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System.out.println(sortedCityArray[2].getNextCity());
System.out.println(sortedCityArray[2].getLengthAB());
System.out.println(sortedCityArray[2].getLengthAroundB());
System.out.println(sortedCityArray[2].getSpeedAB());
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System.out.println(sortedCityArray[3].getLengthAB());
System.out.println(sortedCityArray[3].getLengthAroundB());
System.out.println(sortedCityArray[3].getSpeedAB());
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System.out.println(sortedCityArray[4].getLengthAB());
System.out.println(sortedCityArray[4].getLengthAroundB());
System.out.println(sortedCityArray[4].getSpeedAB());
return cityArray;
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File myFile = new File("I-40cities.txt");
try {
Scanner scan=new Scanner(myFile);
for(int i=0; scan.hasNextLine(); i++){
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city=city.trim();
scan.nextLine();
scan.nextLine();
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catch (Exception e) {
System.out.println(e);
return listOfCities;
public static void main(String args[]) {
Highway h = new Highway("out-of-order.txt");
h.sortCityArray();the ouput is perfect according to the print lines if I use (increase the int where j is in the loop manually by one) :
for(int i=0; i<cityArray.length ;i++)
if(sortedCityArray[0].getNextCity().equals(cityArray.getCity())){
sortedCityArray[0+1]=new City(cityArray[i].getCity(),cityArray[i].getNextCity(),cityArray[i].getLengthAB(),cityArray[i].getLengthAroundB(),cityArray[i].getSpeedAB());
break;
for(int i=0; i<cityArray.length ;i++)
if(sortedCityArray[1].getNextCity().equals(cityArray[i].getCity())){
sortedCityArray[1+1]=new City(cityArray[i].getCity(),cityArray[i].getNextCity(),cityArray[i].getLengthAB(),cityArray[i].getLengthAroundB(),cityArray[i].getSpeedAB());
break;
for(int i=0; i<cityArray.length ;i++)
if(sortedCityArray[2].getNextCity().equals(cityArray[i].getCity())){
sortedCityArray[2+1]=new City(cityArray[i].getCity(),cityArray[i].getNextCity(),cityArray[i].getLengthAB(),cityArray[i].getLengthAroundB(),cityArray[i].getSpeedAB());
break;
for(int i=0; i<cityArray.length ;i++)
if(sortedCityArray[3].getNextCity().equals(cityArray[i].getCity())){
sortedCityArray[3+1]=new City(cityArray[i].getCity(),cityArray[i].getNextCity(),cityArray[i].getLengthAB(),cityArray[i].getLengthAroundB(),cityArray[i].getSpeedAB());
break;
But I cant do this for 200 elements. Are the loops nested right?
Edited by: modplan on Sep 22, 2008 6:49 PM -
How to solve this problem"exception in thread "main" java.lang.noclassdeff"
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add(new Button("Two"));
public Dimension preferredSize()
return new Dimension(200, 100);
public static void main(String [] args)
Frame f = new Frame(" jawtex3");
jawtex3 ex = new jawtex3();
ex.init();
f.add("Center", ex);
f.pack();
f.show();
In this no compilation errors.
I am getting runtime exception.as Exception in thread "main"java.lang.NoClassDefFound Error: jawtex
reply me soon.
thankyou. -
Exception in thread "main" java.lang.Error: Unresolved compilation problem
The following code:
public boolean find(MusbachJ_Person person,BstNode node)
//p.l(person);p.l(node.intData);
if(node.intData.compareTo(person)==0)
return true;
if( node.leftNode != null ) find(person,node.leftNode );
if( node.rightNode != null ) find( person, node.rightNode);
else
return false;
}returns the following compilation error:
Exception in thread "main" java.lang.Error: Unresolved compilation problem:
This method must return a result of type boolean
at MusbachJ_TreeNode.find(MusbachJ_TreeNode.java:32)
at MusbachJ_PeopleTree.main(MusbachJ_PeopleTree.java:91)
But I don't understand, the else statement is right there, what more does it want? Thanks! :)John_Musbach wrote:
Exception in thread "main" java.lang.Error: Unresolved compilation problem: Unresolved compilation problem is an error that you'll only ever see if you're using an IDE. If you used the javac compiler, then you would have seen that the code doesn't even compile.
The reason (as others have pointed out) is, that some paths through your method don't return a value.
I'll re-write your code in the code-style that I usually use, because then it might be easier for you to see the problem:
public boolean find(MusbachJ_Person person,BstNode node)
if(node.intData.compareTo(person)==0) {
return true;
if( node.leftNode != null ) {
find(person,node.leftNode );
if( node.rightNode != null ) {
find( person, node.rightNode);
else {
return false;
}There are two prolbems. I'll spell out the first and let the other one for you to find:
1.) you don't do anything with the return-values of the find-methods you are calling. What do you want to do with them?
2.) What do you return if the current node is not the one that you want and you've got a right node? -
HELP Needed with this error: Exception in thread "main" java.lang.NoClass
Folks,
I am having a problem connecting to my MSDE SQL 2000 DB on a WindowsXP pro. environment. I am learning Java and writing a small test prgm to connect the the database. The code compiles ok, but when I try to execute it i keep getting this error:
"Exception in thread "main" java.lang.NoClassDefFoundError: Test1"
I am using the Microsoft jdbc driver and my CLASSPATH is setup correctly, I've also noticed that several people have complained about this error, but have not seen any solutions....can someone help ?
Here is the one of the test programs that I am using:
import java.sql.*;
* Microsoft SQL Server JDBC test program
public class Test1 {
public Test1() throws Exception {
// Get connection
DriverManager.registerDriver(new
com.microsoft.jdbc.sqlserver.SQLServerDriver());
Connection connection = DriverManager.getConnection(
"jdbc:microsoft:sqlserver://LAPTOP01:1433","sa","sqladmin");
if (connection != null) {
System.out.println();
System.out.println("Successfully connected");
System.out.println();
// Meta data
DatabaseMetaData meta = connection.getMetaData();
System.out.println("\nDriver Information");
System.out.println("Driver Name: "
+ meta.getDriverName());
System.out.println("Driver Version: "
+ meta.getDriverVersion());
System.out.println("\nDatabase Information ");
System.out.println("Database Name: "
+ meta.getDatabaseProductName());
System.out.println("Database Version: "+
meta.getDatabaseProductVersion());
} // Test
public static void main (String args[]) throws Exception {
Test1 test = new Test1();I want to say that there was nothing wrong
with my classpath config., I am still not sure why
that didn't work, there is what I did to resolved
this issue.You can say that all you like but if you are getting NoClassDefFound errors, that's because the class associated with the error is not in your classpath.
(For future reference: you will find it easier to solve problems if you assume that the problem is your fault, instead of trying to blame something else. It almost always is your fault -- at least that's been my experience.)
1. I had to set my DB connection protocol to TCP/IP
(this was not the default), this was done by running
the
file "svrnetcn.exe" and then in the SQL Server Network
Utility window, enable TCP/IP and set the port to
1433.Irrelevant to the classpath problem.
2. I then copied all three of the Microsoft JDBC
driver files to the ..\jre\lib\ext dir of my jdk
installed dir.The classpath always includes all jar files in this directory. That's why doing that fixed your problem. My bet is that you didn't have the jar file containing the driver in your classpath before, you just had the directory containing that jar file.
3. Updated my OS path to located these files
and....BINGO! (that simple)Unnecessary for solving classpath problems.
4. Took a crash course on JDBC & basic Java and now I
have created my database, all tables, scripts,
stored procedures and can read/write and do all kinds
of neat stuff.All's well that ends well. After a few months you'll wonder what all the fuss was about. -
Exception in thread "main" java.lang.NumberFormatException:For input String
this is a code about arrylist. but when I debug it.it metion:Exception in thread "main" java.lang.NumberFormatException:For input String at java.lang.NumberFormatException.forInputString(numberFomatExceptionio java:48)
at java.lang.Integer.parseInt(integer.java:468)
at java.lang.Integer.parseInt(integer.java:497)
at Get.getInt(manerger.java:208)
at LinkList.insertFirst(manager.java:94)
at manager.main(manager.java;20)
this is my code:
import java.io.*;
import java.lang.*;
public class manager
public static void main(String args[]) throws IOException
LinkList list=new LinkList();
System.out.println("input S can scan the grade\ninput D can delete one entry\ninput U can update the entry\ninput A can add one entry\ninput E can end");
int cr=System.in.read();
switch(cr)
case 'A':
list.insertFirst();break;//this is 20 row
case 'S':
System.out.println("input the s");break;
case 'D':
System.out.println("input the d");break;
case 'U':
System.out.println("input the u");break;
class Link
public int number;
public String name=new String();
public int chs;
public int eng;
public int math;
public Link next;
public Link(int number,String name, int chs,int eng,int math)
this.number=number;
this.name=name;
this.chs=chs;
this.eng=eng;
this.math=math;
public Link()
this(0,"",0,0,0);
public void displayLink()
System.out.println(number + " "+name+ " "+chs+ " "+eng+ " "+math+ " ");
class LinkList
public Link first;
public LinkList()
first = null;
public boolean isEmpty()
return first==null;
public void displayList()
System.out.println("");
Link current=first;
while(current!=null)
current.displayLink();
current=current.next;
System.out.println("");
public Link insertFirst() throws IOException
Get getdata=new Get();
int number=getdata.getInt();//this is 94 row
String name=getdata.getString();
int chs=getdata.getInt();
int eng=getdata.getInt();
int math=getdata.getInt();
Link newLink = new Link(number,name,chs,eng,math);
first=newLink;
return first;
public Link find(int key)
Link current=first;
while(current.number!=key)
if(current.next==null)
return null;
else
current=current.next;
return current;
public Link update(int key) throws IOException
Link current=first;
while(current.number!=key)
if(current.next==null)
return null;
else
System.out.println("Input the first letter of the subject:");
int c=System.in.read();
Get get=new Get();
switch(c)
case 'c':
current.chs=get.getInt();break;
case 'e':
current.eng=get.getInt();break;
case 'm':
current.math=get.getInt();break;
return current;
public float average(char key)
Link current=first;
float total=0;
float average=0;
float counter=0;
if(current==null)
return 0;
while(current!=null)
switch(key)
case 'c':
total=current.chs+current.next.chs;break;
case 'e':
total=current.eng+current.next.eng;break;
case 'm':
total=current.math+current.next.math;break;
current=current.next.next;
counter++;
average=total/counter;
return average;
public Link delete(int key)
Link current=first;
Link previous=first;
while(current.number!=key)
if(current.next==null)
return null;
else
previous=current;
current=current.next;
if(current==first)
first=first.next;
else
previous.next=current.next;
return current;
class Get
public static String getString() throws IOException
System.out.println("Input your name:");
InputStreamReader str = new InputStreamReader(System.in);
BufferedReader br = new BufferedReader(str);
String s = br.readLine();
return s;
public static int getInt() throws IOException
System.out.println("Input your data:");
String st = getString();
return Integer.parseInt(st);//this is 208 row
}It may be that the code in getString() returns a
String that ends with a newline. If that is the
problem, you can use
return (Integer.parseInt(st)).trim();1. getString will never return a String ending in newline. BufferedReader.readLine strips off the newline.
2. Even if you had a newline, String.trim doesn't trim newlines.
3. You would need to trim the String, not the int:
return (Integer.parseInt(st.trim()));As JimDinosaur said, you are passing bad data (the value of "st").
In getInt, add this before trying to parse "st":
System.out.println("###"+st+"###");What does it print? -
J2ee server Exception in thread Main java.lang.OutOfMemoryError
hallo
i need your help
first my java j2ee and jdk
j2ee j2sdkee1.3.1
jdk j2sdk 1.4
i nedd the server for jms.
when i started the server with j2ee -verbose
i get the error message:
Starting web service at port: 8000
Exception in thread "Main" java.lang.OutOfMemoryError
what can i do to get out off this error message and starting the server normal. please help me to solve the problem!!!
i read in this forum about -Xms und Xmx but this Commands don't go on my system.
thx for help!!!Hi Warren,
Still I am not clear with your question. But generally this out of memoryspace error can be rectified by changing the properties which comes in the menubar of your command prompt. Then increasing the virtual memory over there. I hope this will help you.
Thanks
Bakrudeen
Technical Support Engineer
Sun MicroSystems Inc, India -
Exception in thread "main" java.lang.UnsupportedClassVersionError:
when i run javac its works fine.when i run java.exe the problem occurs.my jre and other java package is a part of the file that i downloaded from sun.com. i tried to reinstall but i doesn`t help.
Exception in thread "main" java.lang.UnsupportedClassVersionError: NullPointer (Unsupported major.min
or version 49.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
plz help..Hi,
I had the same problem. I got the sam advice about the 'two versions' story.
I was running java programs for Java 1.5 under Win ME (please don't laugh). I then I upgraded to XP. I re-installed Java 1.5. Suddenlu those same programs that were running under ME won't run under XP. Getting the same message as above.
I only had 1 (one) Java version installed. That was Jave 1.5
The funny thing is that jsp pages that I created under ME still worked fine under XP without me doing anything to them
I un-installed Jave 1.5, re-install it and what do you know? Everything is fine now?
It's a strange, strange world we program in, Master Jack (taken from a hit song in the late 60's in SA - need I say more?)
Phlip -
Error exception in thread 'main' java.lang.No ClassDefFound Error
Hi..
i hope maybe some of u can help me to settle this problem...my problem is when i run this program..this error will appear at command prompt....Exception in thread 'main' java.lang.No ClassDefFound Error.
How to solve this problem?I need someone to help me..this is my coding..
import java.io.*;
class Wang{
public int ringgit, sen;
public Wang (int nilaiRinggit, int nilaiSen){
ringgit=nilaiRinggit;
sen=nilaiSen;
System.out.println("Jumlah sen:"+jumlahSen());
public int jumlahSen ( ) {
return 100*ringgit + sen;
class Aplikasi{
public static void main (String [ ] args) throws IOException {
Wang wang = new Wang (5, 20);
System.out.println ("Jumlah wang:RM"+wang.ringgit+"."+wang.sen);
System.out.println("Sen :"+wang.jumlahSen( ) );
thank you...tq for reply my msg..
i dont know how to do....can u help me?....teach me
step by step......to set the classpath...for ur
info.i'm using win xp...i want to ask u about
compilation and run....to compile i using javac
<filename>.java..and to run ... which one true..using
java <filename>.java or java<filename>?For the javac command, FILEname.java is used. For java command CLASSname is used. Do not use .class or .java. Do use the fully qualified CLASS name. Fully qualified means package name plus the Class name. If you do not specify a package name, then the fully qualified name is just the Class name. Also, all names are case sensitive. MyClass is not equal to myclass.
Lets say you compile HelloWorld.java so you have a HelloWorld.class file in the directory, C:\myjava. Then, use the commandjava -classpath c:\myjava HelloWorld
ang how to settle the error exception in thread 'main'
java.lang.Nosuch method error..You should ALWAYS post the full, exact error message. It is difficult to answer this question without knowing the full error. Which method did Java complain about? Often, this occurs when you try to launch a class as an application but the class does not have a method whose signature is "public static void main(String[] args) "
You might want to try the tutorial here: http://java.sun.com/docs/books/tutorial/getStarted/cupojava/index.html
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