关于导致ClassCastException LinkedTreeMap的泛型不能转换为任何

Gson gson = new Gson();
String json = "{\"key\":\"value\"}";
LinkedTreeMap<String, String> map = gson.fromJson(json, LinkedTreeMap.class);
Integer intValue = (Integer) map.get("key"); // 这里会抛出ClassCastException

Gson gson = new Gson();
String json = "{\"key\":\"value\"}";
LinkedTreeMap map = gson.fromJson(json, LinkedTreeMap.class);
String value = (String) map.get("key"); // 这里会抛出ClassCastException

Gson gson = new Gson();
String json = "{\"key\":\"value\"}";
Type type = new TypeToken<LinkedTreeMap<String, String>>() {}.getType();
LinkedTreeMap<String, String> map = gson.fromJson(json, type);
Integer intValue = (Integer) map.get("key"); // 这里会抛出ClassCastException

Gson gson = new Gson();
String json = "{\"key\":\"value\"}";
Type type = new TypeToken<LinkedTreeMap<String, String>>() {}.getType();
LinkedTreeMap<String, String> map = gson.fromJson(json, type);
String value = map.get("key"); // 正确转换为String类型

Gson gson = new GsonBuilder()
        .registerTypeAdapter(Integer.class, new TypeAdapter<Integer>() {
            @Override
            public void write(JsonWriter out, Integer value) throws IOException {
                out.value(value);
            }

            @Override
            public Integer read(JsonReader in) throws IOException {
                if (in.peek() == JsonToken.NULL) {
                    in.nextNull();
                    return null;
                }
                try {
                    return Integer.parseInt(in.nextString());
                } catch (NumberFormatException e) {
                    throw new JsonSyntaxException(e);
                }
            }
        })
        .create();
String json = "{\"key\":\"123\"}";
LinkedTreeMap<String, Object> map = gson.fromJson(json, LinkedTreeMap.class);
Integer intValue = (Integer) map.get("key"); // 正确转换为Integer类型