diff --git a/example/lib/main.dart b/example/lib/main.dart
index 29ee067..23faaa7 100644
--- a/example/lib/main.dart
+++ b/example/lib/main.dart
@@ -139,7 +139,7 @@ void main() {
     LogUtil.e("TimerTick: " + value.toString());
   });
   timerUtil.startTimer();
-  if (timerUtil != null) timerUtil.cancel(); //dispose()
+  timerUtil.cancel(); //dispose()
 
   TimerUtil timerCountDown;
   //倒计时test
diff --git a/lib/src/json_util.dart b/lib/src/json_util.dart
index b10b5a8..6ecf85f 100644
--- a/lib/src/json_util.dart
+++ b/lib/src/json_util.dart
@@ -18,7 +18,7 @@ class JsonUtil {
   static T? getObj<T>(String? source, T f(Map v)) {
     if (source == null || source.isEmpty) return null;
     try {
-      Map map = json.decode(source);
+      Map map = json.decode(source) as Map;
       return f(map);
     } catch (e) {
       print('JsonUtil convert error, Exception：${e.toString()}');
@@ -32,9 +32,9 @@ class JsonUtil {
     try {
       Map map;
       if (source is String) {
-        map = json.decode(source);
+        map = json.decode(source) as Map;
       } else {
-        map = source;
+        map = source as Map;
       }
       return f(map);
     } catch (e) {
@@ -47,12 +47,12 @@ class JsonUtil {
   static List<T>? getObjList<T>(String? source, T f(Map v)) {
     if (source == null || source.isEmpty) return null;
     try {
-      List list = json.decode(source);
-      return list.map((value) {
+      List list = json.decode(source) as List;
+      return list.map((dynamic value) {
         if (value is String) {
           value = json.decode(value);
         }
-        return f(value);
+        return f(value as Map);
       }).toList();
     } catch (e) {
       print('JsonUtil convert error, Exception：${e.toString()}');
@@ -66,15 +66,15 @@ class JsonUtil {
     try {
       List list;
       if (source is String) {
-        list = json.decode(source);
+        list = json.decode(source) as List;
       } else {
-        list = source;
+        list = source as List;
       }
-      return list.map((value) {
+      return list.map((dynamic value) {
         if (value is String) {
           value = json.decode(value);
         }
-        return f(value);
+        return f(value as Map);
       }).toList();
     } catch (e) {
       print('JsonUtil convert error, Exception：${e.toString()}');
@@ -88,11 +88,11 @@ class JsonUtil {
   static List<T>? getList<T>(dynamic source) {
     List? list;
     if (source is String) {
-      list = json.decode(source);
+      list = json.decode(source) as List;
     } else {
-      list = source;
+      list = source as List;
     }
-    return list?.map((v) {
+    return list.map((dynamic v) {
       return v as T;
     }).toList();
   }
diff --git a/lib/src/money_util.dart b/lib/src/money_util.dart
index 2f6b398..2da7e9c 100644
--- a/lib/src/money_util.dart
+++ b/lib/src/money_util.dart
@@ -84,7 +84,7 @@ class MoneyUtil {
   /// yuan to fen.
   /// 元 转 分，
   static int changeY2F(Object yuan) {
-    return NumUtil.multiplyDecStr(yuan.toString(), '100').toInt();
+    return NumUtil.multiplyDecStr(yuan.toString(), '100').toBigInt().toInt();
   }
 
   /// with unit.
diff --git a/lib/src/num_util.dart b/lib/src/num_util.dart
index 84ed4ef..3b9b5e7 100644
--- a/lib/src/num_util.dart
+++ b/lib/src/num_util.dart
@@ -1,4 +1,5 @@
 import 'package:decimal/decimal.dart';
+import 'package:rational/rational.dart';
 
 /**
  * @Author: Sky24n
@@ -131,7 +132,8 @@ class NumUtil {
 
   /// 除
   static Decimal divideDecStr(String a, String b) {
-    return Decimal.parse(a) / Decimal.parse(b);
+    Rational value = Decimal.parse(a) / Decimal.parse(b);
+    return value.toDecimal();
   }
 
   /// 余数