This program:

import java.util.*;
import java.util.concurrent.*;
import static java.lang.System.out;

public class tt {
    public static void main(String[] args) throws Exception {
ConcurrentMap<Long,Long>m = new ConcurrentHashMap<Long,Long>();
out.println(m.put(1L,2L));
out.println(m.remove(1L,null));
out.println(m.remove(1L,null));

    }
}


should print
null
false
false

Instead, it prints
null
true
false

###@###.### 2005-05-18 18:05:40 GMT