java - 传递 arraylist 的副本以避免并发修改异常

Question

我有下面的java代码，它抛出ConcurrentModificationException下面是java代码

下面是正在声明的列表

List<BrokerInvoiceLineItem> brokerInvoiceLineItems= new ArrayList<BrokerInvoiceLineItem>();
            brokerInvoiceLineItems=brokerInvoice.getLineItems();

下面是抛出并发修改异常的代码

if (brokerInvoiceLineItems == null) {
    brokerInvoiceLineItems = brokerInvoiceHome.findLineitemsByInvoiceId(brokerInvoice.getId());
}
for (BrokerInvoiceLineItem brokerInvoiceLineItem : brokerInvoiceLineItems) {
    if (fetchNewAndOldCFandAmend(brokerInvoiceLineItem)) {
        if (!isAnyValid)
            isAnyValid = true;
    }
}

现在的问题是，如果brokerInvoiceLineItems不为空，那么对于第一次迭代，它会进入循环，并且名为isAnyValid的变量的值设置为true，但是一旦第一次迭代结束，那么对于第二次迭代，它会再次进入line for (BrokerInvoiceLineItembrokerInvoiceLineItem :brokerInvoiceLineItems){ 然后它不会进入下一行，它会抛出并发修改异常

所以这意味着它必须在迭代时修改brokerInvoiceLineItems 的大小。这可能发生在 fetchNewAndOldCFandAmend 中，因此我正在考虑制作 BrokerInvoiceLineItems 的副本并修改该副本。所以请告知我如何将副本传递给 fetchNewAndOldCFandAmend(brokerInvoiceLineItem)

还请告知如何使用 copyonwriteArray list 来避免此类错误

Answer 1

我认为当您删除 brokerInvoiceLineItems 的某些项目时，您会遇到此异常。

要避免此异常，请使用迭代器

Iterator<BrokerInvoiceLineItem> iterator = brokerInvoiceLineItems.iterator();
while(iterator.hasNext()) {
  BrokerInvoiceLineItem brokerInvoiceLineItem = iterator.next();
    // your code
}

而不是

for (BrokerInvoiceLineItembrokerInvoiceLineItem:brokerInvoiceLineItems) {

所以你的代码是:

Iterator<BrokerInvoiceLineItem> iterator = brokerInvoiceLineItems.iterator();
while(iterator.hasNext()) {
  BrokerInvoiceLineItem brokerInvoiceLineItem = iterator.next();
  if (fetchNewAndOldCFandAmend(brokerInvoiceLineItem)) {
    if (!isAnyValid)
      isAnyValid = true;
  }
}