Java 中使用 ArrayList 列出用户的共同关注者

SELECT id_follower
FROM followers a
WHERE id_follower IN (
  SELECT id_follower
  FROM followers b
  WHERE a.id_user = b.id_user
) and id_user = ?

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import javax.swing.JOptionPane;

public class SocialNetwork {

    private Connection connection; // 假设已经建立了数据库连接

    public SocialNetwork(Connection connection) {
        this.connection = connection;
    }

    public ArrayList<Object[]> listMutualFollowers(int id_user) {
        ArrayList<Object[]> data = new ArrayList<>();

        String sql = "SELECT id_follower FROM followers a WHERE id_follower IN (SELECT id_follower FROM followers b WHERE a.id_user = b.id_user) and id_user = ?";

        try (PreparedStatement ps = connection.prepareStatement(sql)) {
            ps.setInt(1, id_user);
            try (ResultSet rs = ps.executeQuery()) {
                while (rs.next()) {
                    int followerId = rs.getInt("id_follower");
                    data.add(new Object[]{getFollowerName(followerId)});
                }
            }
        } catch (SQLException e) {
            e.printStackTrace(); // 更好的错误处理
            JOptionPane.showMessageDialog(null, "listMutualFollowers():" + e.getMessage());
            return null;
        }

        return data;
    }

    // 假设存在一个函数，根据 followerId 获取 follower 的名字
    private String getFollowerName(int id_follower) {
        // 实现从数据库或其他数据源获取 follower 名字的逻辑
        return "Follower Name for ID: " + id_follower; // 示例
    }
}