SQL> CREATE DATABASE 'D:\databases\Firebird\data\example.fdb' USER 'SYS' PASSWORD 'пароль' DEFAULT CHARACTER SET WIN1251;
SQL> create table customers(id int not null,name varchar(50));
SQL> insert into customers values (1,'first');
SQL> insert into customers values (2,'второй');
SQL> commit;
SQL> select * from customers;

          ID NAME
============ ==================================================
           1 first
           2 второй

Properties props = new Properties();
        props.setProperty("user", "sys");
        props.setProperty("password", "пароль");
        props.setProperty("encoding", "WIN1251");
        String connection_string=connection_string="jdbc:firebirdsql:192.168.10.41/3050:D:\\databases\\Firebird\\data\\example.fdb";
        boolean st = false;
        Connection con = null;
        PreparedStatement ps = null;
        ResultSet rs = null;
        String Connection_Status = "";
        String value;
        Integer count_values;

        try {
            Class.forName("org.firebirdsql.jdbc.FBDriver");
            Connection connection = DriverManager.getConnection(connection_string, props);
            connection.close();
            Connection_Status = "Подключение к БД " + connection_string + " прошло успешно.";

            try {

                //loading drivers for mysql
                Class.forName("org.firebirdsql.jdbc.FBDriver");

                //creating connection with the database
                con = DriverManager.getConnection
                        (connection_string, props);
                ps = con.prepareStatement
                        (Text_Script);
                //ps.setString(1, uname);
                //ps.setString(2, pass);
                rs = ps.executeQuery();
                //st = rs.next();
                value = "";
                count_values = 0;
                // iterate through the java resultset
                while (rs.next()) {
                    count_values = count_values + 1;
                    value = value + rs.getString("ID") + "; ";
                    value = value + rs.getString("name") +"; ";
}

1; first; 2; ўв®а®©;

c:\Server\Apache\bin>chcp
Текущая кодовая страница: 866
c:\Server\Apache\bin>chcp 1251
Текущая кодовая страница: 1251

SQL> select * from customers;

          ID NAME
============ ==================================================
           1 first
           2 ўв®а®©
           4 зҐвўҐавл©
           5 пятый