So führen Sie Persistenz und Datensicherung in der Java-Entwicklung durch

import java.io.*;

public class FilePersistenceExample {
    public static void main(String[] args) {
        String data = "Hello, World!";
        
        // 写入数据到文件
        try (BufferedWriter writer = new BufferedWriter(new FileWriter("data.txt"))) {
            writer.write(data);
        } catch (IOException e) {
            e.printStackTrace();
        }
        
        // 从文件中读取数据
        try (BufferedReader reader = new BufferedReader(new FileReader("data.txt"))) {
            String line = reader.readLine();
            System.out.println(line);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

import java.sql.*;

public class DatabasePersistenceExample {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String username = "root";
        String password = "password";
        
        try (Connection connection = DriverManager.getConnection(url, username, password)) {
            // 创建表
            String createTableSQL = "CREATE TABLE IF NOT EXISTS userdata (id INT PRIMARY KEY, name VARCHAR(50))";
            try (Statement statement = connection.createStatement()) {
                statement.executeUpdate(createTableSQL);
            }
            
            // 插入数据
            String insertDataSQL = "INSERT INTO userdata (id, name) VALUES (?, ?)";
            try (PreparedStatement statement = connection.prepareStatement(insertDataSQL)) {
                statement.setInt(1, 1);
                statement.setString(2, "John Doe");
                statement.executeUpdate();
            }
            
            // 查询数据
            String selectDataSQL = "SELECT * FROM userdata";
            try (Statement statement = connection.createStatement()) {
                ResultSet resultSet = statement.executeQuery(selectDataSQL);
                while (resultSet.next()) {
                    int id = resultSet.getInt("id");
                    String name = resultSet.getString("name");
                    System.out.println("ID: " + id + ", Name: " + name);
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

import java.io.*;

public class DataBackupExample {
    public static void main(String[] args) {
        String sourceFile = "data.txt";
        String backupFile = "data_backup.txt";
        
        // 复制文件
        try (InputStream inputStream = new FileInputStream(sourceFile);
             OutputStream outputStream = new FileOutputStream(backupFile)) {
            
            byte[] buffer = new byte[1024];
            int length;
            while ((length = inputStream.read(buffer)) > 0) {
                outputStream.write(buffer, 0, length);
            }
            
            System.out.println("数据备份成功");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}