Else is evil

What is the purpose of the else statement?
When you write if statement, you are expressing explicit condition, which the code following if will be executed under. You ensure that the code will run, only when the condition holds. What about else? By using the else, you are stating, that you don't mind the condition, potentially grouping multiple conditions under one statement. To illustrate the point, i will use the snippet of code

int deliveryType = order.getDeliveryType();

if(deliveryType == Delivery.NORMAL) {
   orderQueue.placeOrder(order);
} else {
   orderQueue.placePriorityOrder(order);
}

What's wrong with this code? Everything will work fine, unless there are only two types of order. The code explicitly handles normal order and then groups every other order and treats it the same. As soon as there is new order type added this code would break.

I believe that as the if expresses exactly one condition, the else too should express exactly one condition, or if this is not the case, then it should serve as a guardian. A guardian before the inevitable changes.

int deliveryType = order.getDeliveryType();

if(deliveryType == Delivery.NORMAL) {
   orderQueue.placeOrder(order);
} else if(deliveryType == Delivery.EXPRESS) {
   orderQueue.placePriorityOrder(order);
} else {
   throw new RuntimeException("Unknown delivery type.");
}

The code above illustrates much better approach. The else serves here as a guardian. The application will work, and when there is new delivery type requested it will immediately break unit tests and signal the cause of problem.

if(order.isNew() == true) {
   getOrderDao().save(order);
} else {
   getOrderDao().update(order);
}

Using else here is appropriate too, as it represents exactly one condition. A boolean can never be anything else than true, or false. True or false, two conditions, two branches and there is no way for third.