Add element to vector

Question

class Helloworld{
public static void main(String args[]){
B t1 = new B();
B t2 = new B();
B t3 = new B();
t1.start();
t2.start();
t3.start();
class A extends Thread{
     static Vector v;
     v = new Vector(0,1);
public void packMes(int d, int[] sData, int so, int[] dData, int doa, int size){
         Message m = new Message(d, sData, so, dData, doa, size)   //Message is a data class
         addMessage(m);
     public static synchronized void addMessage(Message pm){
          v.addElement(pm);
class B extends A{
       int[] intArray1 = {1,2,3,4};
       int[] intArray2 = {11,12,13,14};
  public void run(){      
  if (id==0) {     // let id be the name of the current thread i.e "0" means thread-0
     packMes(3, intArray1, 0, intArray2, 0, 4);
     System.out.println("I'm thread "+id+" size: " + v.capacity());
     Message test = (Message) v.elementAt(0);
}I tried to repeat running the program several times. The capacity of the vector in thread-0 is 1 all the time. Unfortunately sometimes it says
I'm thread 0 size: 1
java.lang.ArrayIndexOutOfBoundsException: 0 >= 0
at java.util.v.elementAt(Unknown Source)
at helloWorld.run(B.java:21)
[i]
Please help. Thanks in advance.

Answer 1

here the exact code.
type
java Helloworld 4 B
after compiled.
The same problem still exists although it doesn't happen all the time.
import java.io.*;
import java.util.*;
public class Helloworld{
     static int processor;          // total number of processors
     static String fileName;
     static int counter;          // counter for processors
public static void main(String args[]){
       // interface with users
                processor = Integer.parseInt(args[0]);  
                fileName = args[1];      
     try{     
           Class c = Class.forName(fileName);                
               Thread procs[] = new Thread[processor];             // declare an array for threads
               for (int i=0; i<processor; i++){     
                    System.out.println(i);       // create threads           
          procs[i] = (Thread) c.newInstance();  
               procs.start();                     
     } catch (ClassCastException ex)
          { System.out.println("The file you provided is not a thread"); }
catch (ClassNotFoundException ex)
          { System.out.println("That class doesn't exist");  }
     catch (Exception ex)
          { System.out.println("File error!");             }
class A extends Thread{     
     static Vector v;
     public void createVector(){
          v = new Vector(0,1);
     public void packMes(int desId, int[] sourData, int sourOffset, int[] destData, int destOffset, int size) {
               Message m = new Message(desId, sourData, sourOffset, destData, destOffset, size);
               addMessage(m);
     public int id(){          
          String procsName = getName();
          int procsID=Integer.parseInt(procsName.substring(7));
          return procsID;
     public static void addMessage(Message pm){
          v.addElement(pm);
class B extends A{
     int[] intArray1 = {1,2,3,4};
     int[] intArray2 = {11,12,13,14};
     public void run(){      
          createVector();
          if (id()==0) {     
               packMes(3, intArray1, 0, intArray2, 0, 4);
               System.out.println("I'm thread "+id()+" size: " + v.size());
               Message test = (Message) v.elementAt(0);           
class Message {
     int destID;
     int size;
     public Message(int destID, long[] sourData, int sourOffset, long[] destData, int destOffset, int size) {
          this.destID = destID;
               long[] sData = sourData;
               int sOffset = sourOffset;
               long[] dData = destData;
               int dOffset = destOffset;
               this.size = size;               
     public Message(int destID, int[] sourData, int sourOffset, int[] destData, int destOffset, int size) {
          this.destID = destID;
               int[] sData = sourData;
               int sOffset = sourOffset;
               int[] dData = destData;
               int dOffset = destOffset;
               this.size = size;