多线程 Java 代码的 java.util.ConcurrentModificationException

Question

我在“String name = (String)keys.next();”处收到 ConcurrentModificationException当我在多线程中运行java代码时，一行。导致错误的函数部分如下:

 if (inputStr == null)
        return null;

    String tempStr = new String(inputStr);

    Properties props = System.getProperties();
    Iterator keys = props.keySet().iterator();

    while (keys.hasNext()) {
        String name = (String) keys.next();
        String value = props.getProperty(name);

        //Build a pattern and compile it
        String patternStr = "%" + name + "%";
        Pattern pattern = Pattern.compile(patternStr);

        // Replace all occurrences of pattern in input string
        Matcher matcher = pattern.matcher(tempStr);
        tempStr = matcher.replaceAll(value);
    }

堆栈跟踪详细信息如下:

Caused by: java.util.ConcurrentModificationException at java.util.Hashtable$Enumerator.next(Unknown Source) at com.pb.common.util.ResourceUtil.replaceWithSystemPropertyValues(ResourceUtil.java:350) at com.pb.common.calculator.ControlFileReader.searchAndReplaceWithEnv(ControlFileReader.java:610) at com.pb.common.calculator.ControlFileReader.readMatrixDataEntries(ControlFileReader.java:493) at com.pb.common.calculator.ControlFileReader.(ControlFileReader.java:109) at misc.UtilityExpressionCalculator.(UtilityExpressionCalculator.java:191) at misc.AbstractChoiceHandler.createUtilityExpressionCalculator(AbstractChoiceHandler.java:84) at logSumCalculator.ModeChoiceModel.(ModeChoiceModel.java:41) at logSumCalculator.ModeChoiceTask.run(ModeChoiceTask.java:59)

迭代键的方式是否存在问题？

Answer 1

您需要在迭代时同步属性:

Properties props = System.getProperties();
synchronized(props) {
  // do work here ...
}