举例 Java IO的使用场景及代码

### 回答1：

Java IO的使用场景可以涵盖从文件读写到网络数据流的操作，比如说从本地文件中读取数据到内存，或者从网络中读取文件到本地。以下是一个简单的示例代码，演示了如何使用Java IO从本地文件中读取数据：import java.io.FileReader;
import java.io.BufferedReader;public class ReadFileExample {
public static void main(String[] args) {
try {
FileReader reader = new FileReader("example.txt");
BufferedReader bufferedReader = new BufferedReader(reader);
String line;
while ((line = bufferedReader.readLine()) != null) {
System.out.println(line);
}
reader.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}

### 回答2：
Java IO（输入/输出）是Java编程语言中用于处理输入和输出的机制。它提供了一组类和接口，用于读取和写入不同类型的数据。

以下是几个Java IO的使用场景及相应代码示例：

1. 读取和写入文本文件：

import java.io.*;

public class FileReadWrite {
    public static void main(String[] args) {
        // 读取文件
        try (BufferedReader reader = new BufferedReader(new FileReader("input.txt"))) {
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        // 写入文件
        try (BufferedWriter writer = new BufferedWriter(new FileWriter("output.txt"))) {
            writer.write("Hello, World!");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2. 读取和写入二进制文件：

import java.io.*;

public class BinaryFileReadWrite {
    public static void main(String[] args) {
        // 读取文件
        try (BufferedInputStream inputStream = new BufferedInputStream(new FileInputStream("input.bin"))) {
            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = inputStream.read(buffer)) != -1) {
                System.out.write(buffer, 0, bytesRead);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        // 写入文件
        try (BufferedOutputStream outputStream = new BufferedOutputStream(new FileOutputStream("output.bin"))) {
            byte[] data = {0x48, 0x65, 0x6C, 0x6C, 0x6F, 0x2C, 0x20, 0x57, 0x6F, 0x72, 0x6C, 0x64, 0x21};
            outputStream.write(data);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3. 读取和写入网络连接：

import java.io.*;
import java.net.*;

public class NetworkReadWrite {
    public static void main(String[] args) {
        // 读取网页内容
        try (BufferedReader reader = new BufferedReader(new InputStreamReader(new URL("https://www.example.com").openStream()))) {
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        // 写入HTTP请求
        try {
            URL url = new URL("http://www.example.com");
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("POST");
            connection.setDoOutput(true);
            try (BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(connection.getOutputStream()))) {
                writer.write("data=example");
            }
            
            int responseCode = connection.getResponseCode();
            if (responseCode == HttpURLConnection.HTTP_OK) {
                try (BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()))) {
                    String line;
                    while ((line = reader.readLine()) != null) {
                        System.out.println(line);
                    }
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

这些示例演示了Java IO在不同场景下的用法，包括文件读写和网络连接。实际应用中，Java IO还可以用于处理键盘输入、数据库访问等其他场景。

### 回答3：
Java IO（输入/输出）是Java编程语言中用于处理输入和输出操作的API。它提供了丰富的类和方法，可以用于读取和写入文件、网络操作、序列化和反序列化对象等。以下是一些Java IO的使用场景和相应的代码示例：

1. 读取文件内容并打印每一行：

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class FileReadingExample {
    public static void main(String[] args) {
        try (BufferedReader br = new BufferedReader(new FileReader("filename.txt"))) {
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println(line);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

2. 写入文件内容：

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class FileWritingExample {
    public static void main(String[] args) {
        try (BufferedWriter bw = new BufferedWriter(new FileWriter("filename.txt"))) {
            bw.write("Hello, World!");
            bw.newLine();
            bw.write("This is a line.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

3. 读取网络资源：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;

public class URLReadingExample {
    public static void main(String[] args) {
        try {
            URL url = new URL("http://example.com");
            BufferedReader reader = new BufferedReader(new InputStreamReader(url.openStream()));
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
            reader.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

4. 序列化和反序列化对象：

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;

public class SerializationExample {
    public static void main(String[] args) {
        try {
            MyObject obj = new MyObject("data");
            
            // 序列化对象到文件
            FileOutputStream fos = new FileOutputStream("object.ser");
            ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(obj);
            fos.close();
            
            // 从文件反序列化对象
            FileInputStream fis = new FileInputStream("object.ser");
            ObjectInputStream ois = new ObjectInputStream(fis);
            MyObject deserializedObj = (MyObject) ois.readObject();
            fis.close();
            
            System.out.println(deserializedObj.getData());
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
    
    static class MyObject implements Serializable {
        private String data;
        
        public MyObject(String data) {
            this.data = data;
        }
        
        public String getData() {
            return data;
        }
    }
}

以上是几个Java IO的使用场景及示例代码，展示了如何读取和写入文件、读取网络资源以及序列化和反序列化对象。Java IO是Java编程中常用的功能之一，能处理各种输入和输出操作。