What is the purpose of the Proxy pattern in software development?

The Proxy pattern is used to create a substitute (representative) for another object that controls access to that object. This allows:

• Delaying the creation of a resource-intensive object (lazy initialization).
• Controlling access (e.g., permission checks).
• Logging calls.
• Caching results.

In Java, Proxy is often implemented through interfaces or dynamic proxies.

Example: if you have an object that loads data from the network, a Proxy can first check the cache and return data from there without accessing the network.

interface Image {
    void display();
}

class RealImage implements Image {
    private String filename;
    public RealImage(String filename) {
        this.filename = filename;
        loadFromDisk();
    }
    private void loadFromDisk() {
        System.out.println("Loading " + filename);
    }
    public void display() {
        System.out.println("Displaying " + filename);
    }
}

class ProxyImage implements Image {
    private RealImage realImage;
    private String filename;
    public ProxyImage(String filename) {
        this.filename = filename;
    }
    public void display() {
        if (realImage == null) {
            realImage = new RealImage(filename); // lazy loading
        }
        realImage.display();
    }
}

Here, ProxyImage controls the creation of RealImage and can optimize its usage.