TreeMap.containsKey() 中的奇怪 ClassCastException

Question

这是发生崩溃的那一行

offsetDuration = duration - (offsets.containsKey(freq) 
                    ? offsets.get(freq) : 0l);

我通过捕获Exception 并转储变量得到的值，

long offsetDuration = 0;
long duration = 391144;
TreeMap<Long, Long> offsets = {0=4024974.0, 1036800=8588.0, 1190400=88216.0, 1267200=49763.0, 1497600=87476.0, 1574400=7469.0, 1728000=54553.0, 1958400=60512.0, 2265600=246942.0, 300000=390779.0, 422400=39945.0, 652800=55204.0, 729600=46829.0, 883200=19191.0, 960000=23888.0}
long freq = 300000;

变量TreeMap<Long, Long> offsets是使用下面的代码从一个json文件中解析出来的。

@NonNull
public static TreeMap<Long, Long>  getOffsets(Context context) throws CpuStateException {
    File file = getOffsetsFile(context);
    TreeMap<Long, Long> map;

    try {
        String s = Files.toString(file, Charsets.UTF_8).trim();
        Gson gson = new GsonBuilder().create();
        Type type = new TypeToken<TreeMap<Long, Long>>(){}.getType();
        map = gson.fromJson(s, type);
    } catch (IOException e) {
        throw new CpuStateException("Failed to read offsets!");
    }

    if (map == null)
        throw new CpuStateException("Failed to read offsets!");

    return map;
}

多次检查代码后，我无法确定这段代码可以抛出的情况

java.lang.ClassCastException: java.lang.String cannot be cast to java.lang.Long
    at java.lang.Long.compareTo(Long.java:32)
    at java.util.TreeMap.find(TreeMap.java:277)
    at java.util.TreeMap.findByObject(TreeMap.java:351)
    at java.util.TreeMap.containsKey(TreeMap.java:182)
    at com.vibhinna.library.engine.CpuStates.getCpuData(CpuStates.java:96)
    at com.vibhinna.library.engine.CpuStates.getBarData(CpuStates.java:162)

有什么想法吗？

更新 1：这是生成 json 的方式：

public static void offsetTimers(TreeMap<Long, Long> offsets, Context context) throws CpuStateException {
    Gson gson = new GsonBuilder().create();
    String json = gson.toJson(offsets);
    File file = getOffsetsFile(context);

    try {
        OutputStreamWriter outputStream = new OutputStreamWriter(new FileOutputStream(file),
                "UTF-8");
        outputStream.write(json);
        outputStream.flush();
        outputStream.close();
    } catch (IOException e) {
        throw new CpuStateException("Failed to save offsets!");
    }
}

更新 2 ：即使在原始应用程序中，我什至无法重现此问题，崩溃很少见，只有不到 1% 的客户报告。

更新 3

offset class: class java.lang.String    value: 1036800
offset class: class java.lang.String    value: 1190400
offset class: class java.lang.String    value: 1267200
offset class: class java.lang.String    value: 1497600
offset class: class java.lang.String    value: 1574400
offset class: class java.lang.String    value: 1728000
offset class: class java.lang.String    value: 1958400
offset class: class java.lang.String    value: 2265600
offset class: class java.lang.String    value: 300000
offset class: class java.lang.String    value: 422400
offset class: class java.lang.String    value: 652800
offset class: class java.lang.String    value: 729600
offset class: class java.lang.String    value: 883200
offset class: class java.lang.String    value: 960000

json:

{  
   "0":256093,
   "300000":105045,
   "422400":9677,
   "652800":10443,
   "729600":8868,
   "883200":3951,
   "960000":7323,
   "1036800":18668,
   "1190400":34938,
   "1267200":17151,
   "1497600":11018,
   "1574400":1173,
   "1728000":22881,
   "1958400":21076,
   "2265600":66501
}

Answer 1

这是看起来有效的丑陋解决方法。

@NonNull
public static TreeMap<Long, Long>  getOffsets(Context context) throws CpuStateException {
    File file = getOffsetsFile(context);
    TreeMap map;

    try {
        String s = Files.toString(file, Charsets.UTF_8).trim();
        Gson gson = new GsonBuilder().create();
        Type type = new TypeToken<TreeMap<Long, Long>>(){}.getType();
        map = gson.fromJson(s, type);
    } catch (IOException e) {
        throw new CpuStateException("Failed to read offsets!");
    }

    if (map == null)
        throw new CpuStateException("Failed to read offsets!");

    // So, I don't trust Gson. On some devices the above code seems to be producing a
    // TreeMap<String, Double/Float>. So let's assume it's either a String or a boxed primitive.
    // Even if the assumption is wrong we're no worse off than we were before.
    // The String we'll parse, the primitive we'll cast. Brace yourselves for a horrible hack!
    // TODO find a proper fix.
    Iterator it = map.keySet().iterator();
    TreeMap<Long, Long> treeMap = new TreeMap<>();
    while (it.hasNext()) {
        Object key = it.next();
        Object value = map.get(key);
        Long lKey, lValue;

        if ((key instanceof Long)) {
            lKey = (Long) key;
        } else {
            Log.e(TAG, "Invalid key type in TreeMap: " + key.getClass());
            if (key instanceof Number) {
                lKey = ((Number) key).longValue();
            } else if (key instanceof String) {
                lKey = Double.valueOf((String) key).longValue();
            } else {
                throw new IllegalArgumentException("Invalid key in TreeMap: "  + key);
            }
        }

        if ((value instanceof Long)) {
            lValue = (Long) value;
        } else {
            Log.e(TAG, "Invalid value type in TreeMap: " + value.getClass());
            if (value instanceof Number) {
                lValue = ((Number) value).longValue();
            } else if (value instanceof String) {
                lValue = Double.valueOf((String) value).longValue();
            } else {
                throw new IllegalArgumentException("Invalid value in TreeMap: " + value);
            }
        }
        treeMap.put(lKey, lValue);
    }

    return treeMap;
}