How Can the Strategy Pattern Solve Encryption Challenges for Files of Varying Sizes?

Real-World Application of the Strategy Pattern: Encryption Strategies

The Strategy Pattern adheres to the Open-Closed Principle, allowing for flexibility and extensibility in software design. While common examples like validation based on order status exist, this pattern finds practical applications in various real-world scenarios.

Encryption Strategies

Consider the task of encrypting a file. For small files, an in-memory strategy can be employed, where the entire file is loaded into memory and encrypted. However, for large files, a different strategy is required to avoid memory overflow issues.

In this case, a "swap-to-disk" strategy can be implemented, where the file is encrypted in parts and the intermediate results are stored in temporary files.

Implementation Details

Using the Strategy Pattern, we can define a common interface for the encryption task:

interface Cipher {
    public void performAction();
}

Two concrete implementation strategies are defined:

class InMemoryCipherStrategy implements Cipher {
    public void performAction() {
        // Load file into memory and encrypt
    }
}

class SwapToDiskCipherStrategy implements Cipher {
    public void performAction() {
        // Swap partial results to disk and encrypt
    }
}

The client code can use the "CipherFactory" to retrieve the appropriate strategy based on the file size:

File file = getFile();
Cipher c = CipherFactory.getCipher(file.size());
c.performAction();

Benefits of Using the Strategy Pattern

By employing the Strategy Pattern, we adhere to the OCP, separating the encryption algorithm from the client code. This allows for easy extension to support new encryption algorithms or different file size scenarios without modifying the client code.

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