🚧 remove new keyword to get inline with dart 2 code standard.

stateful_widget/lib/main.dart

@@ -1,15 +1,15 @@
 import 'package:flutter/material.dart';
 
 void main() {
-  runApp(new MaterialApp(
-    home: new MyButton(),
+  runApp(MaterialApp(
+    home: MyButton(),
   ));
 }
 
 class MyButton extends StatefulWidget {
   @override
   MyButtonState createState() {
-    return new MyButtonState();
+    return MyButtonState();
   }
 }
 
@@ -27,22 +27,22 @@ class MyButtonState extends State<MyButton> {
 
   @override
   Widget build(BuildContext context) {
-    return new Scaffold(
-      appBar: new AppBar(
-        title: new Text("Stateful Widget"),
+    return Scaffold(
+      appBar: AppBar(
+        title: Text("Stateful Widget"),
         backgroundColor: Colors.green,
       ),
-      body: new Container(
-        child: new Center(
-          child: new Column(
+      body: Container(
+        child: Center(
+          child: Column(
             mainAxisAlignment: MainAxisAlignment.center,
             children: <Widget>[
-              new Text(displayedString, style: new TextStyle(fontSize: 40.0)),
-              new Padding(padding: new EdgeInsets.all(10.0)),
-              new RaisedButton(
-                child: new Text(
+              Text(displayedString, style: TextStyle(fontSize: 40.0)),
+              Padding(padding: EdgeInsets.all(10.0)),
+              RaisedButton(
+                child: Text(
                   "Press me",
-                  style: new TextStyle(color: Colors.white),
+                  style: TextStyle(color: Colors.white),
                 ),
                 color: Colors.red,
                 onPressed: onPressOfButton,