实现 eclipse对mysql 增删改查四种方法的 功能

先建一个类 这个类是用来存放增删改查四种方法的，然后在建一个测试类 这个类写main方法 然后在main方法中 调用增删改查四种方法
注意：写查询的方法时，要求打印出id username password这三个字段

网上有很多类似的博客，可以搜一下就有

 
import java.io.DataInputStream;
import java.io.IOException;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class a {
    // JDBC连接信息
    private static final String URL = "jdbc:mysql://localhost:3306/test_db";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "123456";

    // 添加数据
    public void insertData(String username, String password) {
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            String query = "INSERT INTO users(username, password) VALUES (?, ?)";
            PreparedStatement statement = conn.prepareStatement(query);
            statement.setString(1, username);
            statement.setString(2, password);
            statement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 删除数据
    public void deleteData(int id) {
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            String query = "DELETE FROM users WHERE id = ?";
            PreparedStatement statement = conn.prepareStatement(query);
            statement.setInt(1, id);
            statement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 修改数据
    public void updateData(int id, String newUsername, String newPassword) {
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            String query = "UPDATE users SET username = ?, password = ? WHERE id = ?";
            PreparedStatement statement = conn.prepareStatement(query);
            statement.setString(1, newUsername);
            statement.setString(2, newPassword);
            statement.setInt(3, id);
            statement.executeUpdate();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 查询数据
    public List<String[]> queryData() {
        List<String[]> resultList = new ArrayList<>();
        try (Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            String query = "SELECT id, username, password FROM users";
            Statement statement = conn.createStatement();
            ResultSet resultSet = statement.executeQuery(query);
            while (resultSet.next()) {
                int id = resultSet.getInt("id");
                String username = resultSet.getString("username");
                String password = resultSet.getString("password");
                String[] row = {String.valueOf(id), username, password};
                System.out.println("ID: " + id + ", Username: " + username + ", Password: " + password);
                resultList.add(row);
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return resultList;
    }


}



import java.util.List;
import java.util.Scanner;

public class b {
    public static void main(String[] args) {
        a a=new a();
        a.insertData("Alice", "123456");
        a.insertData("Bob", "abcdef");

        a.deleteData(1);

        a.updateData(2, "Charlie","888");
        List<String[]> strings= a.queryData();
    }

}