There is a race condition in the java.util.Vector class. It occurs because the single
argument version of lastIndexOf reads elementCount without being synchronized.
 A different thread can remove elements and trim the array before the synchronized
version of lastIndexOf is invoked, causing an array bounds exception.

Run the following program using "java C":

---
import java.util.*;

class Shared extends Thread {

    static public Vector v;
    static {
v = new Vector();
v.addElement(v);
v.addElement(v);
v.addElement(v);
    }

    static void Sleep(int mills) {
try {
Thread.sleep(mills);
} catch (Exception e) {
}
    }
    
    public void run() {
synchronized(v) {
Sleep(200);
v.removeElementAt(0);
v.trimToSize();
}
    }
}


class C extends Thread{
    public void run(){
Shared.Sleep(100);
Shared.v.lastIndexOf(Shared.v);
    }

  public static void main(String args[]){
      new Shared().start();
      new C().start();
  }
}

---
it outputs the following:

~/proj> java C
java.lang.ArrayIndexOutOfBoundsException
        at java.util.Vector.lastIndexOf(Compiled Code)
        at java.util.Vector.lastIndexOf(Compiled Code)
        at C.run(Compiled Code)
~/proj>


Here is the version information, but the same bug appears all versions:
~/proj> java -version
java version "1.1.7B-2"
~/proj> java -fullversion
java full version "JDK1.1.7:01/04/1999-19:30"
(Review ID: 95322)
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