在今天做android当项目，我遇到了这个异常，好吧。其实最不寻常遇到异常IllegalstateException。它们与我们的硬件连接SDK抛出，我想折磨学生阿玉啊。扯远了。

今天，我想回到这个异常。java.util.ConcurrentModificationException异常，一開始我愣了一下。貌似从来没遇到过这个，然后果断百度大神。这才发现：

原因是你遍历该集合时。对该集合进行了删除元素的操作导致的。假设你有删除元素的必要，建议赋值到还有一个集合，然后对他进行删除操作.

偶出现错误的地方：

if (serverCards != null) {for (PaymentCard serverCard : serverCards) {MstCard matchingMstCard = findMatchingMstCard(serverCard,mstCards);ChargecaseCard matchingChargecaseCard = findMatchingChargecaseCard(serverCard, chargecaseCards);if (matchingMstCard != null && matchingChargecaseCard != null) {matchingMstCard.setDominantColor(serverCard.getDominantColor());matchingChargecaseCard.setDominantColor(serverCard.getDominantColor());unifiedCards.add(new UnifiedCard(matchingMstCard,serverCard, matchingChargecaseCard));mstOnlyCards.remove(matchingMstCard);chargecaseOnlyCards.remove(matchingChargecaseCard);} else if (matchingMstCard != null&& matchingChargecaseCard == null) {matchingMstCard.setDominantColor(serverCard.getDominantColor());unifiedCards.add(new UnifiedCard(matchingMstCard,serverCard));mstOnlyCards.remove(matchingMstCard);} else if (matchingMstCard == null&& matchingChargecaseCard != null) {matchingChargecaseCard.setDominantColor(serverCard.getDominantColor());unifiedCards.add(new UnifiedCard(serverCard,matchingChargecaseCard));chargecaseOnlyCards.remove(matchingChargecaseCard);} else {serverOnlyCards.add(serverCard);}}}for (MstCard card : mstOnlyCards) {ChargecaseCard matchingChargecaseCard = findMatchingChargecaseCard(card, chargecaseCards);if (matchingChargecaseCard != null) {matchingChargecaseCard.setDominantColor(card.getDominantColor());unifiedCards.add(new UnifiedCard(card, null,matchingChargecaseCard));chargecaseOnlyCards.remove(matchingChargecaseCard);} else {unifiedCards.add(new UnifiedCard(card));}}for (ChargecaseCard card : chargecaseOnlyCards) {unifiedCards.add(new UnifiedCard(card));}for (PaymentCard card : serverOnlyCards) {unifiedCards.add(new UnifiedCard(card));}return unifiedCards;

在一个for循环中mstOnlyCards调用了，mstOnlyCards.remove()方法。

特记录之，引以为戒。