What is fly weight pattern?

Fly weight pattern is useful where we need to create many objects and all these objects share some kind of common data. Consider figure ‘Objects and common data’. We need to print visiting card for all employees in the organization. So we have two parts of data one is the variable data i.e. the employee name and the other is static data i.e. address. We can minimize memory by just keeping one copy of the static data and referencing the same data in all objects of variable data. So we create different copies of variable data, but reference the same … Click here to continue reading.

Can you explain adapter pattern?

Many times two classes are incompatible because of incompatible interfaces. Adapter helps us to wrap a class around the existing class and make the classes compatible with each other. Consider the below figure ‘Incompatible interfaces’ both of them are collections to hold string values. Both of them have a method which helps us to add string in to the collection. One of the methods is named as ‘Add’ and the other as ‘Push’. One of them uses the collection object and the other the stack. We want to make the stack object compatible with the collection object.

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Difference between Visitor Pattern and Strategy Pattern?

Visitor and strategy look very much similar as they deal with encapsulating complex logic from data. We can say visitor is more general form of strategy.

In strategy we have one context or a single logical data on which multiple algorithms operate. In the previous questions we have explained the fundamentals of strategy and visitor. So let’s understand the same by using examples which we have understood previously. In strategy we have a single context and multiple algorithms work on it. Figure ‘Strategy’ shows how we have a one data context and multiple algorithm work on it.

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Can you explain visitor pattern?

Visitor pattern allows us to change the class structure with out changing the actual class. Its way of separating the logic and algorithm from the current data structure. Due to this you can add new logic to the current data structure with out altering the structure. Second you can alter the structure with out touching the logic.

Consider the below figure ‘Logic and data structure’ where we have a customer data structure. Every customer object has multiple address objects and every address object had multiple phone objects. This data structure needs to be displayed in two different formats one is … Click here to continue reading.

Can you explain strategy pattern?

Strategy pattern are algorithms inside a class which can be interchanged depending on the class used. This pattern is useful when you want to decide on runtime which algorithm to be used.

Let’s try to see an example of how strategy pattern works practically. Let’s take an example of a math’s calculation where we have strategies like add and substract. Figure ‘Strategy in action’ shows the same in a pictorial format. It takes two numbers and the depending on the strategy it gives out results. So if it’s an addition strategy it will add the numbers, if it’s a substraction … Click here to continue reading.