missedMSRB是一个列表,其中包含2187个元素,并且在尝试运行以下代码段时
List<List<String>> subList = getSubList(missedMSRB, 1000);
for (List<String> subMSRB : subList) {
StringBuffer sql = new StringBuffer(NamedQueries.msSQL);
sql.append("(");
for (int i1 = 0; i1 < subMSRB.size(); i1++) { //Line 463 Throws Exception
if (i1 < subMSRB.size() - 1) {
sql.append("?,");
} else {
sql.append("? )");
}
} ....
代码失败,出现以下异常,任何有关为什么我要进行并发修改以及如何摆脱相同建议的建议
13 Jan 2015 10:42:58,974 [main] ERROR RunAnalytics: General Error: null
java.util.ConcurrentModificationException
at java.util.ArrayList$SubList.checkForComodification(ArrayList.java:1169)
at java.util.ArrayList$SubList.size(ArrayList.java:998)
at com.abc.Analytics.RunAnalytics.getCountCheck(RunAnalytics.java:463)
at com.abc.Analytics.RunAnalytics.analyticsExecute(RunAnalytics.java:342)
at com.abc.Analytics.RunAnalytics.main(RunAnalytics.java:84)
下面的剩余代码
PreparedStatement psMSQL2 = msSQL.prepareStatement(sql.toString());
psMSQL2.setString(1, runDate);
psMSQL2.setString(2, runDate2);
int i = 3;
for (String s : subMSRB) {
psMSQL2.setString(i, s.trim());
i++;
}
ResultSet msSQL = psMSQL2.executeQuery();
logger.debug("SQL executed");
while (msSQL.next()) {
missedMSRB.remove(msSQL.getString(1));
}
getSubList impl //已更正
public static List<List<String>> getSubList(List<String> inputList, int subListSize) {
int listSize = inputList.size();
int noOfLoops = listSize / subListSize;
int remainingListSize = listSize % subListSize;
List<List<String>> subList = new ArrayList<List<String>>();
for (int i = 0; i < noOfLoops; i++) {
int fromIndex = i * subListSize;
int toIndex = (fromIndex) + subListSize;
subList.add(new ArrayList<String>(inputList.subList(fromIndex, toIndex)));
if ((remainingListSize != 0)
&& (toIndex == (listSize - remainingListSize))) {
subList.add(new ArrayList<String>(inputList.subList(toIndex, listSize)));
}
}
return subList;
}
最佳答案
在getSubList
中,使用inputList.subList
创建多个列表。在List
中实现的ArrayList
中的此方法不会创建新的列表。相反,它返回inputList
的视图,因此由inputList
支持。
对inputList
的任何修改都会对子列表产生影响。您已将missedMSRB
作为inputList
传入,因此对missedMSRB
的任何修改都会影响subList
因此,在外部missedMSRB.remove
循环中调用for
时,将为ConcurrentModification
中的所有列表创建一个subList
。然后,当您检查subList
中此列表之一的大小时,它将引发ConcurrentModificationException
为了解决这个问题,您可以例如创建一个新列表,而不是直接使用subList
的结果:
subList.add(new ArrayList<String>(inputList.subList(fromIndex, toIndex)));
关于java - 此代码块的并发修改异常,请帮助?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/27925960/