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    Question

    Which design pattern is best suited for ensuring that a

    class has only one instance and provides a global point of access to it?
    A Factory Pattern Correct Answer Incorrect Answer
    B Singleton Pattern Correct Answer Incorrect Answer
    C Observer Pattern Correct Answer Incorrect Answer
    D Strategy Pattern Correct Answer Incorrect Answer
    E Prototype Pattern Correct Answer Incorrect Answer

    Solution

    The Singleton Pattern ensures that a class has only one instance and provides a global point of access to it. It is often used for managing shared resources like a database connection pool, logging, or configuration settings. This pattern works by restricting the class's instantiation and providing a static method to get the single instance. Singleton is particularly useful when exactly one object is required to coordinate actions across the system. This pattern is implemented by making the constructor private, storing the single instance as a static property, and providing a public static method to access it. It ensures thread safety and lazy initialization in multi-threaded applications when implemented carefully. Explanation of Incorrect Options: A) Factory Pattern : The Factory Pattern focuses on creating objects without specifying their exact classes. It abstracts the instantiation process, allowing for flexibility in object creation. However, it does not restrict the number of instances or provide a global access point, making it unsuitable for the problem described. C) Observer Pattern : The Observer Pattern defines a one-to-many dependency between objects, where changes in one object are automatically reflected in dependent objects. It is ideal for event-driven systems but does not restrict the number of instances or provide global access, making it incorrect. D) Strategy Pattern : The Strategy Pattern allows behavior to be selected at runtime by encapsulating algorithms in separate classes. While it promotes flexibility, it does not deal with instance control or global access, making it irrelevant to the Singleton problem. E) Prototype Pattern : The Prototype Pattern involves creating new objects by copying existing ones rather than instantiating new ones. It is useful for object duplication but does not restrict the number of instances, hence it is not applicable here.

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