This program:

import java.util.*;
import java.util.concurrent.*;

public class Bug {
    public static void main(String[] args) throws Throwable {
Collection<Integer> c = new LinkedBlockingQueue<Integer>();
Integer[] a = new Integer[1];
a[0] = 42;
System.out.println(c.toArray(a)[0]);
    }
}

should print "null", but actually prints 42.