java - Java：将 Map.keySet() 保存到 ArrayList 会引发 StackOverflowError

Question

我正在编写电梯模拟程序。如果我只运行几次模拟（大约：1-50 次），通常不会发生 StackOverflowError。但是，我必须大约运行模拟。1000 次。

我有不同的课程。执行以下命令时，错误发生在类“n_AlgorithmMain”中：
waitingPassengerId = new ArrayList<>(waitingPassengerMap.keySet());。“WaitingPassengerId”的创建方式如下：
private List<Integer> waitingPassengerId;。

整个功能是：

protected LinkedListMultimap<Integer, Integer> filledInsidePassengerMap(LinkedListMultimap<Integer,Integer> waitingPassengerMap, int currentFloor){

    servedWaitingPassengerId = new ArrayList<>();

    waitingPassengerId = new ArrayList<>(waitingPassengerMap.keySet());

    for(int i = 0; i < waitingPassengerId.size() ; i++){
        waitingPassengerValues = waitingPassengerMap.get(waitingPassengerId.get(i));
        passengerStartFloor = fetchPassengerStartFloor(waitingPassengerValues);
        if(passengerStartFloor == currentFloor){
            for(int j = 0; j < waitingPassengerValues.size(); j++){
                insidePassengerMap.put(waitingPassengerId.get(i), waitingPassengerValues.get(j));
            }
            servedWaitingPassengerId.add(waitingPassengerId.get(i)); 
        }
    }
    waitingPassengerMap = adjustedMap(waitingPassengerMap, servedWaitingPassengerId);
    return insidePassengerMap;
}

我不确定，但问题可能是由“n_AlgorithmStandard”类中的以下代码触发的，因为上述函数是从“n_AlgorithmStandard”调用的：
insidePassengerMap = filledInsidePassengerMap(standardWaitingPassengerMap, standardCurrentFloor);。

我认为它也会在以下行触发，目前尚未达到：
finishedPassengerMap = filledFinishedPassengerMap(insidePassengerMap, standardCurrentFloor);.

这些映射初始化如下：

private LinkedListMultimap<Integer, Integer> insidePassengerMap = LinkedListMultimap.create();
和
private LinkedListMultimap<Integer, Integer> finishedPassengerMap = LinkedListMultimap.create();。

“n_AlgorithmStandard”中的整个函数如下所示：

private void processOneFloor() {

    standardWaitingPassengerMap = filledWaitingPassengerMap(timeMap, standardCurrentFloor, isRfid, emptyRandomAmountList); 
    currentSumRandomAmount = getSumRandomAmount();

    insidePassengerMap = filledInsidePassengerMap(standardWaitingPassengerMap, standardCurrentFloor);
    finishedPassengerMap = filledFinishedPassengerMap(insidePassengerMap, standardCurrentFloor);

    moveElevator();

    if (currentSumRandomAmount < passengerAmountTotal) {
        processOneFloor();
    } else if (currentSumRandomAmount == passengerAmountTotal){
        processRemainingPassengers(standardWaitingPassengerMap, insidePassengerMap);
        remainingPassengersAmountStandard = getRemainingPassengersAmount();

        for (int i = 0; i < remainingPassengersAmountStandard; i++){
            processOneFloor();
        }
    }
}

错误：

Exception in thread "main" java.lang.StackOverflowError
at java.util.HashMap.putVal(HashMap.java:629)
at java.util.HashMap.put(HashMap.java:612)
at java.util.HashSet.add(HashSet.java:220)
at com.google.common.collect.LinkedListMultimap$DistinctKeyIterator.next(LinkedListMultimap.java:448)
at java.util.Iterator.forEachRemaining(Iterator.java:116)
at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
at n_AlgorithmMain.filledInsidePassengerMap(n_AlgorithmMain.java:309)
at n_AlgorithmStandard.processOneFloor(n_AlgorithmStandard.java:142)

最后一行在 Stacktrace 中出现了 100 次。

标签： javaarraylistlinked-listhashmapstack-overflow