带有迭代器的java.util.ConcurrentModificationException

我知道如果要尝试通过简单循环将其从集合循环中删除，我将收到此异常：java.util.ConcurrentModificationException。但是我正在使用Iterator，它仍然会产生此异常。知道为什么以及如何解决吗？

HashSet<TableRecord> tableRecords = new HashSet<>();

...

    for (Iterator<TableRecord> iterator = tableRecords.iterator(); iterator.hasNext(); ) {
        TableRecord record = iterator.next();
        if (record.getDependency() == null) {
            for (Iterator<TableRecord> dependencyIt = tableRecords.iterator(); dependencyIt.hasNext(); ) {
                TableRecord dependency = dependencyIt.next(); //Here is the line which throws this exception
                if (dependency.getDependency() != null && dependency.getDependency().getId().equals(record.getId())) {
                    tableRecords.remove(record);
                }
            }
        }
    }