Gustavo Siqueira

I'm getting a ClassNotFoundException to try read object from socket. In Eclipse, I send an object that belongs the package com.messenger.client.User to the Socket. So, I build a jar file to that package.
Now, I going to Terminal Linux e run my server socket with the command javac -cp User.jar Server.java, then java Server

import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.io.ObjectInputStream; import java.net.Inet6Address; import java.net.InetAddress; import java.net.ServerSocket; import java.net.Socket; import com.messenger.client.User; public class Server { public static void main(String[] args) { new Server(); } /** * Create a Server Socket */ public Server() { try { ServerSocket ss = new ServerSocket(5959); while(true) { System.out.println("Waiting client.."); Socket socket = ss.accept(); //each socket an user connected ObjectInputStream in = new ObjectInputStream(socket.getInputStream()); User user; user = (User) in.readObject(); System.out.println("User connected: " + user.getNickname()); user.setSocket(socket); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch(ClassNotFoundException e) { e.printStackTrace(); } } }

However, appears the following error:

java.lang.ClassNotFoundException: com.messenger.client.User at java.net.URLClassLoader$1.run(URLClassLoader.java:366) at java.net.URLClassLoader$1.run(URLClassLoader.java:355) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:354) at java.lang.ClassLoader.loadClass(ClassLoader.java:425) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308) at java.lang.ClassLoader.loadClass(ClassLoader.java:358) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:270) at java.io.ObjectInputStream.resolveClass(ObjectInputStream.java:625) at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1612) at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1517) at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1771) at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1350) at java.io.ObjectInputStream.readObject(ObjectInputStream.java:370) at Server.<init>(Server.java:42) at Server.main(Server.java:17)

[SOLVED]

After several attempts, problem was resolved. I compiled the Server with javac Server.java then java -cp User.jar Server.

Researching the title "Sun Certified Programmer for Java 6", I found the pdf available through from java.net. I would like if is legal or illegal.

In order to learn better regards between protocols TCP/IP and Socket, I solved make a simple web chat (desktop). I need to knows how many users are connected to socket, so I thought in store objects sockets in a ArrayList<Socket> in then return object socket for RMI. That's the better idea to that ? Other issue: How do I send the message to particular socket connected ?
Can someone me give advice ? Thank you!

The problem was solved! Thanks you!

Sure. We will return again. I have three class named: "Initial", "DisplayDocument" and "OpenFile"

Initial Class - That class have all functions to display a frame and menus to call another class. In other words, she extends JFrame.

DisplayDocument Class - That class is accountable for display the contents that the user opened in menu that contains in the "Initial" class, call "OpenFile".

OpenFile Class - That class implements ActionListener to listen the button "Open File" called by the user.

The issue is: I want display the contents of the file in the "DisplayDocument" class, just that.

In class "Initial" I already add the class DisplayDocuments. Therefore, when I run the program, that class already called.

Do you is with problem to understand my issue ?

Do you not understood my issue ?

I'm sorry. Do you can me give an example to fix it the problem ?
O code is compiling, however, is not displayed the componentes within of classe "DisplayDocument".

Sure: See an example:

The "Initial" class, add the "DisplayDocument" to your JFrame, once "Initial" extends JFrame. Therefore we will add:
frame.add(new DisplayDocument());

In this same class, I have a button that will request to user to open file:

private JMenuItem getMenuItemOpenFile() { menuitem = new JMenuItem(); menuitem.setText("Open file"); menuitem.addActionListener(new OpenFile()); return menuitem; }

Thus, the "OpenFile" class, does all your functions to open the file required by the user:

public void actionPerformed(ActionEvent e) { //Does the configurations to open file. }

Now, to have a good concept of OO, I though in display the file in the "DisplayDocument" class:

public class DisplayDocument extends JPanel { public DisplayDocument() { } }

Thereby, I tryed created a instance from "DisplayDocument" or extends the "DisplayDocument" class to add components to it. However, not it worked!

In order, to a good concept of OO, I though in display contents of the class ''OpenFile" once called by the class "Initial" with "ActionListener" to open a file. Thus, "OpenFile" implements 'ActionListener' to open the file called by the class "Initial" that contains JFrame. Now, to display the contents of the file open by the user, I want display it in separate class. So, I created the class "ShowDocument" that extends JPanel to display the file open in the class "OpenFile". However, not is working creating a instance of 'ShowDocument'.

Thanks you in advance!

Thanks you, Steve!

Thanks for your explanation!
I'm comprising. So, once that this algorithm is called divide-and-conquer, is a ways for to solve a given problem. Alright. But, because it is considered like worst-case in (theta of n-squared) ?
In terms of running time, this delay algorithm for run. In addition of algorithm to solve a problem, it has that run in time fast. There is a algorithm called Insertion sort, that in little lines make sorted of numbers.
For example, see the following exercise from book "Introduction to Algorithms":

We can express insertion sort as a recursive procedure as follows. In order to sort A[1..n], we recursively sort A[1..n-1] and then insert A[n] into the sorted array A[1..n-1]. Write a recurrence for the worst-case running time of this recursive version of insertion sort.

If possible, do you can me say exactly what means that such of 'worst-case' ? I really can not understand it.

I'm reading the book "Introduction to Algorithms". So, I caught this algorithm in this book. You no response my question: Why the method is executed three times for after to go to other method following ?

Hi, everyone!
I'm studying a algorithm called merge sort, in which i did in Java. But, I'm having problems to understand it.

import java.io.*; import java.util.*; public class MergeSort { public static void merge(int[] A, int p, int q, int r) { System.out.println("BEGIN method 'merge: '"); System.out.println(); System.out.println("value of p " + p); System.out.println("value of q " + q); System.out.println("value of r " + r); int n1 = q-p+1; // 5 int n2 = r-q; // 2 System.out.println("value of n1: " + n1); System.out.println("value of n2: " + n2); int[] L = new int[n1+1]; // 6 int[] R = new int[n2+1]; // 3 for (int i=0; i<n1; i++) { L[i] = A[p+i]; } for (int j=0; j<n2; j++) { R[j] = A[q+j +1]; } L[n1] = 10000; //for infinity R[n2] = 10000; int i=0; int j=0; for (int k=p; k<=r; k++) { if (L[i] <= R[j]){ A[k] = L[i]; i++; } else { A[k] = R[j]; j++; } } System.out.println("END of method merge."); } public static void mergeSort (int[] A, int p, int r) { System.out.println("EXECUTING METHOD 'mergeSort': "); System.out.println("value of p " + p); System.out.println("value of r " + r); if (p<r) { int q = (p+r)/2; System.out.println("Within of the if"); System.out.println("Value of q: " + q); System.out.println(); System.out.println("Run method mergeSort 1"); mergeSort(A, p, q); System.out.println(); System.out.println("Run method mergeSort 2"); mergeSort(A, q+1, r); System.out.println(); merge(A, p, q, r); System.out.println("EXECUTING METHOD 'merge': "); System.out.println("p " + p); System.out.println("q " + q); System.out.println("r " + r); System.out.println(); } } public static void main(String args[]) { int A[] = {5,2,4,7,1,3,2,6}; System.out.println(A.length-1); mergeSort(A,1,A.length-1); for(int teste = 0; teste < A.length;teste++) { System.out.println(A[teste]); } } }

So, when I run the program, is called the method mergeSort for to make the sorting of numbers. After , make the 'if', then is executed the method mergeSort(A, p, q); three times, and just after is executed the method mergeSort(A, q+1, r). Why that happens ?

Thanks you!

Hello,
Yes.. The data not are being sent through from request.getParameter.

Hello,

I'm trying develop a Newsletter with Javamail. So I thought in to use the ckeditor for the user send emails. However, I can't get values with servlet (request.getParameter("message");). The value is as blank.
How can to fix problem ?

Thanks you!