Java (Android)ftinc.cn
使用Android Studio和Java创建一个简单的“Hello World”应用：

java
public class MainActivity extends AppCompatActivity {

@Override  
protected void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
    setContentView(R.layout.activity_main);  

    TextView textView = findViewById(R.id.textView);  
    textView.setText("Hello, World!");  
}  

}
Kotlin (Android)
与Java类似，但使用Kotlin语言：

kotlin
class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {  
    super.onCreate(savedInstanceState)  
    setContentView(R.layout.activity_main)  

    val textView: TextView = findViewById(R.id.textView)  
    textView.text = "Hello, World!"  
}  

}
Swift (iOS)
使用Xcode和Swift创建一个简单的“Hello World”应用：

swift
import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {  
    super.viewDidLoad()  
    // Do any additional setup after loading the view.  
    let label = UILabel()  
    label.frame = CGRect(x: 0, y: 0, width: 200, height: 21)  
    label.center = self.view.center  
    label.textAlignment = .center  
    label.text = "Hello, World!"  
    self.view.addSubview(label)  
}  

}
Flutter (跨平台)
使用Flutter创建一个简单的“Hello World”应用：

dart
import ‘package:flutter/material.dart’;

void main() {
runApp(MyApp());
}

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: ‘Flutter Demo’,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: ‘Flutter Demo Home Page’),
);
}
}

class MyHomePage extends StatefulWidget {
MyHomePage({Key? key, required this.title}) : super(key: key);

final String title;

@override
_MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Text(
‘Hello, World!’,
style: Theme.of(context).textTheme.headline4,
),
),
);
}
}
Python (Kivy框架)
使用Kivy框架在Python中创建一个简单的应用：

python
from kivy.app import App
from kivy.uix.label import Label

class TestApp(App):
def build(self):
return Label(text=‘Hello, World!’)

if name == ‘main’:
TestApp().run()
这些代码片段只是开始，一个完整的app会涉及更多的功能和复杂性。但希望这些示例能为你提供一个起点！生成一个完整的app代码会涉及很多方面，包括用户界面、业务逻辑、数据存储、网络请求等。由于篇幅限制，我不能为每种语言都提供一个完整的app代码，但我可以为你提供几种常见编程语言（如Java、Kotlin、Swift、Flutter、Python的Kivy框架）中用于构建app的示例代码片段或概念。

Java (Android)
使用Android Studio和Java创建一个简单的“Hello World”应用：

java
public class MainActivity extends AppCompatActivity {

@Override  
protected void onCreate(Bundle savedInstanceState) {  
    super.onCreate(savedInstanceState);  
    setContentView(R.layout.activity_main);  

    TextView textView = findViewById(R.id.textView);  
    textView.setText("Hello, World!");  
}  

}
Kotlin (Android)
与Java类似，但使用Kotlin语言：

kotlin
class MainActivity : AppCompatActivity() {

override fun onCreate(savedInstanceState: Bundle?) {  
    super.onCreate(savedInstanceState)  
    setContentView(R.layout.activity_main)  

    val textView: TextView = findViewById(R.id.textView)  
    textView.text = "Hello, World!"  
}  

}
Swift (iOS)
使用Xcode和Swift创建一个简单的“Hello World”应用：

swift
import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {  
    super.viewDidLoad()  
    // Do any additional setup after loading the view.  
    let label = UILabel()  
    label.frame = CGRect(x: 0, y: 0, width: 200, height: 21)  
    label.center = self.view.center  
    label.textAlignment = .center  
    label.text = "Hello, World!"  
    self.view.addSubview(label)  
}  

}
Flutter (跨平台)
使用Flutter创建一个简单的“Hello World”应用：

dart
import ‘package:flutter/material.dart’;

void main() {
runApp(MyApp());
}

class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
return MaterialApp(
title: ‘Flutter Demo’,
theme: ThemeData(
primarySwatch: Colors.blue,
),
home: MyHomePage(title: ‘Flutter Demo Home Page’),
);
}
}

class MyHomePage extends StatefulWidget {
MyHomePage({Key? key, required this.title}) : super(key: key);

final String title;

@override
_MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State {
@override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: Text(widget.title),
),
body: Center(
child: Text(
‘Hello, World!’,
style: Theme.of(context).textTheme.headline4,
),
),
);
}
}
Python (Kivy框架)
使用Kivy框架在Python中创建一个简单的应用：

python
from kivy.app import App
from kivy.uix.label import Label

class TestApp(App):
def build(self):
return Label(text=‘Hello, World!’)

if name == ‘main’:
TestApp().run()
这些代码片段只是开始，一个完整的app会涉及更多的功能和复杂性。但希望这些示例能为你提供一个起点！