Replace the dart code in the lib/main.dart file with the below code

import 'package:flutter/material.dart'; 
 
void main() => runApp(MyApp()); 
 
class MyApp extends StatelessWidget { 
  // This widget is the root of your application. 
  @override 
  Widget build(BuildContext context) { 
    return MaterialApp( 
      title: 'Hello World Demo Application', 
      theme: ThemeData( 
        primarySwatch: Colors.blue, 
      ), 
      home: MyHomePage(title: 'Home page'), 
    ); 
  } 
} 
 
class MyHomePage extends StatelessWidget { 
  MyHomePage({Key key, this.title}) : super(key: key); 
 
  final String title; 
 
  @override 
  Widget build(BuildContext context) { 
    return Scaffold( 
      appBar: AppBar( 
        title: Text(this.title), 
      ), 
      body: Center( 
        child: 
            Text( 
              'Hello World', 
            ) 
      ), 
    ); 
  } 
}