Java标准库中的IO操作，如读写文件，网络通信等案例分析

原创超、凢脫俗 2024-12-04 22:09 23阅读 0赞

在Java标准库中，IO（Input/Output）操作主要通过以下几个类和接口来实现：

1. File：代表一个文件或目录。进行读写等IO操作。

案例：
```java
import java.io.File;

public class FileExample {
    public static void main(String[] args) {
        // 创建一个File对象，代表当前工作目录
        File currentDir = new File();

// 检查当前目录是否存在
        if (currentDir.exists()) {
            System.out.println("Current directory exists: " + currentDir.getAbsolutePath());
            // 进行读写操作，这里以写入内容为例
            try {
                String content = "Hello, Java!";
                File fileToWrite = new File(currentDir, "example.txt"));
                Files.write(fileToWrite.toPath(), content.getBytes(StandardCharsets.UTF_8)));
                System.out.println("Content written successfully to: " + fileToWrite.getAbsolutePath());
            } catch (IOException e) {
                System.err.println("Error occurred while writing content: " + e.getMessage());
                e.printStackTrace();
            }
        } else {
            System.out.println("Current directory does not exist.");
        }
    }
}
```
2. InputStream/OutputStream：提供读写字节流的API。

案例：
```java
import java.io.*;

public class IOExample {
    public static void main(String[] args) throws IOException {
        // 1. 创建一个文件对象，用于读写操作
        File file = new File("example.txt");

// 2. 检查文件是否存在，不存在则创建
        if (file.exists()) {
            System.out.println("File already exists: " + file.getAbsolutePath());

// 3. 如果要写入内容，则使用输出流
            try (OutputStream outputStream = new FileOutputStream(file)) {
                byte[] content = "Hello, Java!".getBytes(StandardCharsets.UTF_8));
                outputStream.write(content);
                System.out.println("Content written successfully to the file.");
            } catch (IOException e) {
                System.err.println("Error occurred while writing content: " + e.getMessage());
                e.printStackTrace();
            }
        } else {
            System.out.println("File does not exist, creating now...");
            // 创建新文件
            try (OutputStream outputStream = new FileOutputStream(file)) {
                byte[] content = "Hello, Java!".getBytes(StandardCharsets.UTF_8));
                outputStream.write(content);
                System.out.println("New file created successfully.");
            } catch (IOException e) {
                System.err.println("Error occurred while creating file: " + e.getMessage());
                e.printStackTrace();
            }
        }
    }
}
```
3. Network通信：使用java.net包中的类来实现网络通信，例如Socket、ServerSocket等。

案例：
```java
import java.io.*;
import java.net.*;

public class NetworkingExample {
    public static void main(String[] args) throws IOException, SocketException {
        // 创建Socket连接服务器
        String serverHost = "localhost"; // 本地服务器IP地址或域名
        int serverPort = 8080; // 服务器端口

try (Socket socket = new Socket(serverHost, serverPort))) {
            System.out.println("Connected to server successfully...");

// 创建输出流，用于发送数据
            OutputStream outputStream = socket.getOutputStream();

// 发送字符串数据
            String messageToSend = "Hello, Server!";
            byte[] messageBytes = messageToSend.getBytes(StandardCharsets.UTF_8));
            outputStream.write(messageBytes);

// 接收服务器响应数据
            InputStream inputStream = socket.getInputStream();
            BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream)));
            String responseFromServer;
            while ((responseFromServer = reader.readLine())) != null) {
                System.out.println("Received server response: " + responseFromServer));
            }
        } catch (SocketException e) {
            System.err.println("Error occurred while establishing socket connection: " + e.getMessage());
            e.printStackTrace();
        } catch (IOException e) {
            System.err.println("Error occurred while sending/receiving data from server: " + e.getMessage());
            e.printStackTrace();
        }
    }
}
```
以上案例展示了Java标准库中IO操作的几种常见方式，包括读写文件、网络通信等。