mysql语句传入java变量

import java.sql.*;

public class MySQLExample {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String user = "username";
        String password = "password";

        try (Connection conn = DriverManager.getConnection(url, user, password)) {
            String sql = "SELECT * FROM users WHERE username = ? AND password = ?";
            try (PreparedStatement pstmt = conn.prepareStatement(sql)) {
                pstmt.setString(1, "admin");
                pstmt.setString(2, "password");

                try (ResultSet rs = pstmt.executeQuery()) {
                    while (rs.next()) {
                        System.out.println("User found: " + rs.getString("username"));
                    }
                }
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

String sql = "SELECT * FROM users WHERE username = ? AND password = ?";
try (PreparedStatement pstmt = conn.prepareStatement(sql)) {
    pstmt.setString(1, userInputUsername);
    pstmt.setString(2, userInputPassword);
    // 执行查询
}

String url = "jdbc:mysql://localhost:3306/mydatabase";
String user = "username";
String password = "password";
try (Connection conn = DriverManager.getConnection(url, user, password)) {
    // 连接成功
} catch (SQLException e) {
    e.printStackTrace();
}

pstmt.setInt(1, userId); // 假设userId是int类型