如何在Java insert预准备语句中用空字符串替换空值

import java.sql.*;

public class InsertExample {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/database_name";
        String username = "username";
        String password = "password";
        
        try {
            // 创建数据库连接
            Connection conn = DriverManager.getConnection(url, username, password);
            
            // SQL插入语句
            String sql = "INSERT INTO table_name (column1, column2, column3) VALUES (?, ?, ?)";
            
            // 创建预准备语句
            PreparedStatement pstmt = conn.prepareStatement(sql);
            
            // 设置参数
            String value1 = "";  // 空值
            String value2 = "Hello";
            String value3 = "";  // 空值
            
            // 替换空值为空字符串
            if (value1 == null) {
                value1 = "";
            }
            if (value3 == null) {
                value3 = "";
            }
            
            pstmt.setString(1, value1);
            pstmt.setString(2, value2);
            pstmt.setString(3, value3);
            
            // 执行插入语句
            int rows = pstmt.executeUpdate();
            System.out.println("Inserted " + rows + " rows.");
            
            // 关闭连接
            pstmt.close();
            conn.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}