Re: Vector (was Re: Change character in string)

Bent C Dalager <>
Fri, 13 Mar 2009 23:07:49 +0000 (UTC)
On 2009-03-13, Andreas Leitgeb <> wrote:

Based on how long it took you to spot it, it's quite likely that
RGB fell for the same misread, when he/she tried it in eclipse.
This case closed. (unless RGB speaks up, that is)

The contest is still open, with (now corrected):
 ? List<Foo> lf= Collections.synchronizedList(new ArrayList<Foo>());
 ? List<Foo> lf= new Vector<Foo>();
Scores so far:
  half a point to the former for being in line with other
      Collection implementations' synchronized wrappings.
  quarter of a point to the latter for being shorter to write.
  half a point to the latter for being "slightly faster" according to Sun.

I am going to take this as an invitation to vent my pet peeve with
Vector again (even if I don't really understand what the contest is
all about). My apologies if it has been mentioned before in this
thread - I'm something of a latecomer to the discussion.

In the context of the above quoted text, the following program works
fine with a synchronized ArrayList but deadlocks with Vector. This has
been the case forever and I just checked it now with JDK6_12 on
Ubuntu: still a deadlock.

Switch the comment around in createList() to deadlock or not deadlock.

As far as I can recall, the difference between the two is that Vector
synchronizes equals() while the synchronizedList() wrapper
doesn't. It's been a while though so don't take that as gospel.

    Bent D

import java.util.*;

public class Test
   public static void main(String args[])
      List<Integer> a = createList();
      List<Integer> b = createList();
      Thread t1 = new Thread(new MyRunnable(a, b)); // spot the difference
      Thread t2 = new Thread(new MyRunnable(b, a)); // spot the difference

   private static List<Integer> createList()
      //return Collections.synchronizedList(new ArrayList<Integer>());
      return new Vector<Integer>();

   private static void populate(List<Integer> l)
      for (int ii = 0; ii < 1000; ++ii) l.add(ii);

   static class MyRunnable implements Runnable
      List<Integer> list1, list2;
      public MyRunnable(List<Integer> l1, List<Integer> l2)
         list1 = l1;
         list2 = l2;
      public void run()
          for (int ii = 0; ii < 1000; ++ii) list1.equals(list2);

Bent Dalager - -
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