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，如果你有删除元素的必要，建议赋值到另一个集合，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。
android细节之java.util.ConcurrentModificationException异常,布布扣,bubuko.com