//জাভা (Java)
public class DatabaseConnectionExample {
    public static class PostgreSQLDB {
        public void Connect() {
            System.out.println(“Connecting to PostgreSQL database”);
        }
    }
    public static class SQLiteDatabase {
        public void Connect() {
            System.out.println(“Connecting to SQLite database”);
        }
    }
    public static class MSSQLServerDB {
        public void Connect() throws Exception {
            throw new Exception(“Cannot connect to MSSQL Server”);
        }
    }
    public static void ConnectToMSSQLServerDatabase(MSSQLServerDB db) {
        try {
            db.Connect();
            System.out.println(“Successfully connected to ” + db.getClass().getName() + “\n”);
        } catch (Exception ex) {
            System.out.println(“Error connecting to database: ” + ex.getMessage() + “\n”);
        }
    }
    public static void ConnectToPostgreSQLDatabase(PostgreSQLDB db) {
        try {
            db.Connect();
            System.out.println(“Successfully connected to ” + db.getClass().getName() + “\n”);
        } catch (Exception ex) {
            System.out.println(“Error connecting to database: ” + ex.getMessage() + “\n”);
        }
    }
    public static void ConnectToSQLiteDatabase(SQLiteDatabase db) {
        try {
            db.Connect();
            System.out.println(“Successfully connected to ” + db.getClass().getName() + “\n”);
        } catch (Exception ex) {
            System.out.println(“Error connecting to database: ” + ex.getMessage() + “\n”);
        }
    }
    public static void main(String[] args) {
        Object[] databases = {
            new PostgreSQLDB(),
            new SQLiteDatabase(),
            new MSSQLServerDB(),
        };
        for (Object db : databases) {
            if (db instanceof PostgreSQLDB) {
                ConnectToPostgreSQLDatabase((PostgreSQLDB) db);
            } else if (db instanceof SQLiteDatabase) {
                ConnectToSQLiteDatabase((SQLiteDatabase) db);
            } else if (db instanceof MSSQLServerDB) {
                ConnectToMSSQLServerDatabase((MSSQLServerDB) db);
            }
        }
    }
}

//জাভা (Java) – Output
Connecting to PostgreSQL database
Successfully connected to DatabaseConnectionExample$PostgreSQLDB
Connecting to SQLite database
Successfully connected to DatabaseConnectionExample$SQLiteDatabase
Error connecting to database: Cannot connect to MSSQL Server

using System;
using System.Collections.Generic;
namespace DatabaseConnectionExample
{
	public class PostgreSQLDB
	{
		public void Connect()
		{
			Console.WriteLine(“Connecting to PostgreSQL database”);
		}
	}
	public class SQLiteDatabase
	{
		public void Connect()
		{
			Console.WriteLine(“Connecting to SQLite database”);
		}
	}
	public class MSSQLServerDB
	{
		public void Connect()
		{
			throw new Exception(“Cannot connect to MSSQL Server”);
		}
	}
	class Program
	{
		public static void ConnectToMSSQLServerDatabase(MSSQLServerDB db)
		{
			try
			{
				db.Connect();
				Console.WriteLine($”Successfully connected to {db.GetType().Name}\n”);
			}
			catch (Exception ex)
			{
				Console.WriteLine($”Error connecting to database: {ex.Message}\n”);
			}
		}
		public static void ConnectToPostgreSQLDatabase(PostgreSQLDB db)
		{
			try
			{
				db.Connect();
				Console.WriteLine($”Successfully connected to {db.GetType().Name}\n”);
			}
			catch (Exception ex)
			{
				Console.WriteLine($”Error connecting to database: {ex.Message}\n”);
			}
		}
		public static void ConnectToSQLiteDatabase(SQLiteDatabase db)
		{
			try
			{
				db.Connect();
				Console.WriteLine($”Successfully connected to {db.GetType().Name}\n”);
			}
			catch (Exception ex)
			{
				Console.WriteLine($”Error connecting to database: {ex.Message}\n”);
			}
		}
		static void Main(string[] args)
		{
			// Create a list of databases to connect to
			List databases = new List()
			{new PostgreSQLDB(), new SQLiteDatabase(), new MSSQLServerDB()};
			// Loop through the list and call the appropriate connect method for each database
			foreach (var db in databases)
			{
				if (db is PostgreSQLDB)
				{
					ConnectToPostgreSQLDatabase((PostgreSQLDB)db);
				}
				else if (db is SQLiteDatabase)
				{
					ConnectToSQLiteDatabase((SQLiteDatabase)db);
				}
				else if (db is MSSQLServerDB)
				{
					ConnectToMSSQLServerDatabase((MSSQLServerDB)db);
				}
			}
		}
	}
}

//Output – আউটপুট
Connecting to PostgreSQL database
Successfully connected to PostgreSQLDB
Connecting to SQLite database
Successfully connected to SQLiteDatabase
Error connecting to database: Cannot connect to MSSQL Server