How Can the Strategy Pattern Solve Real-World Encryption Challenges with Varying File Sizes?

Real-World Encryption: A Strategy Pattern Solution

The Strategy Pattern offers a powerful solution for managing diverse algorithms or behaviors within interchangeable objects, known as strategies. This design pattern enhances flexibility and adheres to the Open/Closed Principle (OCP) by abstracting and isolating the underlying logic.

File encryption presents a prime example. Different approaches are needed for small versus large files:

Small File Encryption (In-Memory Strategy):

Ideal for smaller files (e.g., under 1 GB), this strategy loads the entire file into memory, encrypts it, and completes the process in a single operation.

Large File Encryption (Swap-to-Disk Strategy):

Larger files require a different approach. The swap-to-disk strategy processes the file in chunks. Each chunk is loaded into memory, encrypted, and then written to a temporary file. This prevents memory overload.

Client-side encryption code remains consistent, regardless of file size:

<code class="language-java">File file = getFile();
Cipher c = CipherFactory.getCipher(file.size());
c.encrypt();</code>

The factory method determines the appropriate strategy based on file size:

<code class="language-java">interface Cipher {
    void encrypt();
}

class InMemoryCipher implements Cipher {
    public void encrypt() {
        // Load file into byte array and encrypt...
    }
}

class SwapToDiskCipher implements Cipher {
    public void encrypt() {
        // Process file in chunks, writing encrypted data to temporary files...
    }
}</code>

The CipherFactory selects and returns the correct Cipher implementation.

In essence, the Strategy Pattern allows for different encryption methods based on file size, ensuring maintainability and extensibility while upholding the Open/Closed Principle.

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