access object in a vector

[mark smith]

hi

i have a vector and i put some PrintWriter to it...
i do that to be able to send message to all client connected to a server

i would like to put a msg to each PrintWriter

public void sendMsgToAll(String msg){
    for(int i=0;i<vecConnection.size()-1;i++)
       vecConnection.elementAt(i).println("msg:" + msg);
}

i get

ServeurMulti.java:20: cannot find symbol
symbol : method println(java.lang.String)
location: class java.lang.Object
vecConnection.elementAt(i).println("msg:" + msg);


thanks

[marc weber]

References stored in Vectors are implicitly upcast to type Object, so when you pull them back out, you need to explicitly downcast them back to their correct type.

[Scott Selikoff]

And just to nitpick...

It is strongly recommended you add brackets {} around the statements in your for() loop. Especially since you may need to add a line to cast them (although not required).

Second, don't use Vector, use ArrayList. Vector is used only when synchronization is required which can still be accomplished using ArrayLists with synchronized access methods.

Finally, if this is a public method you should probably check that the Vector itself is not null unless you've got very good encapsulation for modifying it.

[mark smith]

ok i tried this

 public void sendMsgToAll(String msg){
        PrintWriter out;// = new PrintWriter();
        for(int i=0;i<vecConnection.size()-1;i++){
            out=(PrintWriter)vecConnection.elementAt(i);
            out.println("msg:" + msg);
        }
    }

why i try to insert a PrintWriter object into the vector

the proram crash

java said:

ServeurMultiThread.java:27: warning: [unchecked] unchecked call to add(E) as a member of the raw type java.util.Vector
vecConnection.add(out);
^

[Scott Selikoff]

Could you post the code that the system is throwing the error on, specifically the lines surrounding "vecConnection.add(out);"?

If you are using Java 1.5, you should use generics when you create the array.

[mark smith]

ya i use java 1.5

import java.net.*;
import java.io.*;
import java.util.Vector;
public class ServeurMulti extends Thread{
    public int myPort;
    boolean listening = true;
 
    private Vector msgClient;
    private Vector vecClient;
    private Vector vecConnection;
 
    public ServeurMulti(int port){
        myPort=port;
    }
 
    public void sendMsgToAll(String msg){
        PrintWriter out;
        for(int i=0;i<vecConnection.size()-1;i++){
            out=(PrintWriter)vecConnection.elementAt(i);
            out.println("msg:" + msg);
        }
    }
 
    public void run(){
        ServerSocket serverSocket = null;
        Socket s=null;
        try{
            System.out.println("server run client connection, wait connecting port: " + myPort);
            serverSocket = new ServerSocket(myPort);
            while (listening){
                s=serverSocket.accept();
                new ServeurMultiThread(s, vecConnection, msgClient).start();
            }
        }catch (IOException e) {
        }
    }
}

import java.net.*;
import java.io.*;
import java.util.Vector;
 
public class ServeurMultiThread extends Thread{
 
    private Socket socket = null;
    private Vector vecConnection;
    private Vector msgClient;
 
    public ServeurMultiThread(Socket socket, Vector connect, Vector msg){
        super("ServeurMultiThread");
        this.socket = socket;
        this.msgClient=msg;
        this.vecConnection=connect;
    }
 
    public void run(){
 
        try{
 
            System.out.println("wait data.....");
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
 
            /*add connection to vector*/
            vecConnection.add(out);
 
            String inputLine, outputLine;
            ProtocolServeurClient protocol = new ProtocolServeurClient();
            outputLine=protocol.processInput(null, socket);
            out.println(outputLine);
 
            while ((inputLine = in.readLine()) != null) {
 
                //msgClient.add(inputLine);
 
                System.out.println("client> " + inputLine);
                outputLine=protocol.processInput(inputLine,socket);
                out.println(outputLine);
            }
            out.close();
            in.close();
            socket.close();
        }catch (IOException e) {
        }
    }
}

[marc weber]

As Scott indicated, this is related to generics in Java 1.5. Collections now use generics to safeguard the types of references they contain, and the compiler is simply warning you of potentially unsafe operations.

In this case, your type is not just Vector. It's Vector<PrintWriter>. For example...

Vector<PrintWriter> myWriters = new Vector<PrintWriter>();

(The message you posted above looks like what you would get after recompiling with -Xlint to show details of the warnings.)
[ December 07, 2005: Message edited by: marc weber ]

[mark smith]

Originally posted by marc weber:
[QB]As Scott indicated, this is related to generics in Java 1.5. Collections now use generics to safeguard the types of references they contain, and the compiler is simply warning you of potentially unsafe operations.

In this case, your type is not just Vector. It's Vector<PrintWriter>. For example...

Vector<PrintWriter> myWriters = new Vector<PrintWriter>();

(The message you posted above looks like what you would get after recompiling with -Xlint to show details of the warnings.)

ok now with you line Vector... the program don't crash...
ya i recompiling with -Xlint and got the same warning...

  
import java.net.*;
import java.io.*;
import java.util.Vector;
 
public class ServeurMultiThread extends Thread{
 
    private Socket socket = null;
    private Vector vecConnection;
    private Vector msgClient;
 
    public ServeurMultiThread(Socket socket, Vector connect, Vector msg){
        super("ServeurMultiThread");
        this.socket = socket;
        this.msgClient=msg;
        this.vecConnection=connect;
    }
 
    public void run(){
 
        try{
 
            System.out.println("wait data.....");
            PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
 
            vecConnection.add(out);
 
            String inputLine, outputLine;
            ProtocolServeurClient protocol = new ProtocolServeurClient();
            outputLine=protocol.processInput(null, socket);
            out.println(outputLine);
 
            while ((inputLine = in.readLine()) != null) {
 
                System.out.println("client> " + inputLine);
                outputLine=protocol.processInput(inputLine,socket);
 
                //sendMsgToAll(inputLine);
                //don't need the ligne below... if sendMsgToAll work
                //out.println(outputLine);
            }
            out.close();
            in.close();
            socket.close();
        }catch (IOException e) {
        }
    }
}

what is the best way to have access to sendMsgToAll method?