在Java編程中，經常需要導入和導出數據。這可能是從一個文件中讀取數據，將數據插入到數據庫中，或將數據從數據庫中導出為文件。以下是一些常見的導入和導出數據方法。

//從文件中讀取數據
try {
File file = new File("data.txt");
Scanner scanner = new Scanner(file);
while (scanner.hasNextLine()) {
String data = scanner.nextLine();
System.out.println(data);
}
scanner.close();
} catch (FileNotFoundException e) {
System.out.println("文件不存在。");
}
//將數據插入到數據庫中
String url = "jdbc:mysql://localhost:3306/mydatabase";
String username = "username";
String password = "password";
try (Connection conn = DriverManager.getConnection(url, username, password);
Statement stmt = conn.createStatement()) {
String sql = "INSERT INTO mytable (name, age) VALUES ('John', 25)";
stmt.executeUpdate(sql);
System.out.println("插入成功。");
} catch (SQLException e) {
System.out.println(e.getMessage());
}
//將數據從數據庫中導出為文件
try (Connection conn = DriverManager.getConnection(url, username, password);
Statement stmt = conn.createStatement()) {
String sql = "SELECT * FROM mytable";
ResultSet result = stmt.executeQuery(sql);
FileWriter writer = new FileWriter("data.txt");
while (result.next()) {
String name = result.getString("name");
int age = result.getInt("age");
writer.write(name + ", " + age + "\n");
}
writer.close();
System.out.println("導出成功。");
} catch (SQLException e) {
System.out.println(e.getMessage());
} catch (IOException e) {
System.out.println(e.getMessage());
}