public class PostalZipCode
{
    private String barCode;
 
    public PostalZipCode(String zipCode)
    {
        determinateBarCode(zipCode);
    }
 
    private void determinateBarCode(String zipCode)
    {
        //do what ever calculation you need to generate barCode
        setBarCode(GENERATED_STRING_FOR_BARCODE_HERE);
    }
 
    private void setBarCode(String str)
    {
        barCode = str;
    }
 
    public void getBarCode()
    {
        return barCode;
    }
}