请帮我解决这个问题。我让Graph by Structure HashMap> graf表示,我需要遍历hashmap并设置和删除一些边。我该怎么做呢?代码给了我这个异常
Exception in thread "main" java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(Unknown Source)
at java.util.HashMap$KeyIterator.next(Unknown Source)