it serves to that service for that particular client.




Let us consider an example of a restaurant, which is based on command pattern structure. Where the first step is the order from the customer to the waiter for the food. In the next command or step waiter takes the order and forwards the order to the cook in the kitchen. The cook can make various types of food but now he prepares the ordered item and hands it over to the waiter who in turn serves to the customer.

Let us consider this example in term of java code. As we know that the first step is the order. The order is made of command in which the customer gives the order for the food to the waiter.
Order.java

package bahavioral.command; public class Order { private String cmd; public Order(String cmd) {
this.cmd = cmd;
}
}

The next step is belonging to the waiter who takes the order and forwards it to the cook. After that waiter calls the prepareFood method of the cook who in turn cooks.

Waiter.java

package bahavioral.command; public class Waiter {
public Food takeOrder(Customer cust, Order ord) {
Cook cook = new Cook();
Food food = cook.prepareOrder(ord, this);
return food;
}
}

The waiter takes command and wraps it in an order; the order is linked to a specific customer. For, the cook, the order is linked to a cook and also Food is linked to the Order.
Cook.java

package bahavioral.command; public class Cook {
public Food prepareOrder(Order ord, Waiter wtr) {
Food food = getCookedFood(ord); return food;
}
public Food getCookedFood(Order ord) {
Food food = new Food(ord);
return food;
}

Here, the waiter takes command and wraps it in an order; the order is associated to a particular customer. The order is associated to a cook and also Food is associated to the Order.

The order is an object, which depends on the command. The food item will change as soon as the command changes. This is loose coupling between the client and the implementation.

Interpreter Pattern:

The Interpreter Pattern is a design pattern that defines a grammatical representation for a language along with an interpreter to interpret sentences in the language. The best example of an interpreted language is Java itself, which converts the English-written code to a byte code format, so that all the operating systems can understand it.