[Kaffe] I am getting a ConcurrentModificationException

Moses DeJong dejong at cs.umn.edu
Mon Sep 27 09:53:25 PDT 1999

> However, this exception indicates that your program potentially
> has a bug.. it's trying to iterate through the elements while
> changing the contents of the Hashtable at the same time.
> -Archie

I wrote a little test program to double check that what I was doing
was correct. I was using the Hashtable.keys() method to iterate a
table and remove each key like the following example.

import java.util.*;

public class HashTest {
    public static void main(String[] argv) {
	Hashtable h = new Hashtable();
	Enumeration search;
	String elem;

	h.put("one", new Integer(1));
	h.put("two", new Integer(2));
	h.put("three", new Integer(3));

	for (search = h.keys(); search.hasMoreElements() ; ) {
	    elem = (String) search.nextElement();

	    System.out.print("elem is \"" + elem + "\" value is " +
h.get(elem) + " ... ");

This program works just fine in JDK 1.1.7 from Blackdown.

% java HashTest
elem is "one" value is 1 ... removed
elem is "three" value is 3 ... removed
elem is "two" value is 2 ... removed

With Archie's latest changes it also works under with Kaffe from the CVS
(Mon Sep 27)

% kaffe HashTest
elem is "three" value is 3 ... removed
elem is "one" value is 1 ... removed
elem is "two" value is 2 ... removed

So it looks like this problem has been solved. Thanks Archie.

Mo DeJong

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