Proxy pattern in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare the Proxy class implementing the Subject interface.

LLD

class Proxy implements [1] {
    private RealSubject realSubject;

    public void request() {
        if (realSubject == null) {
            realSubject = new RealSubject();
        }
        realSubject.request();
    }
}

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AProxy

BSubject

CRealSubject

DClient

Attempts:

3 left

💡 Hint

Common Mistakes

Using RealSubject instead of Subject as the implemented interface.

Not implementing any interface.

Implementing Proxy interface which does not exist.

The Proxy class must implement the Subject interface to act as a substitute for RealSubject.

2fill in blank

medium

Complete the code to forward the request from Proxy to RealSubject.

LLD

public void request() {
    if (realSubject == null) {
        realSubject = new RealSubject();
    }
    realSubject.[1]();
}

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Arequest

Bexecute

Chandle

Dprocess

Attempts:

3 left

💡 Hint

Common Mistakes

Using method names not defined in the Subject interface.

Calling a method that does not exist in RealSubject.

The Proxy forwards the call to the RealSubject's request() method.

3fill in blank

hard

Fix the error in the Proxy constructor to initialize the RealSubject lazily.

LLD

public Proxy() {
    [1] = null;
}

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Asubject

BRealSubject

CrealSubject

Dproxy

Attempts:

3 left

💡 Hint

Common Mistakes

Using the class name RealSubject instead of the variable name.

Initializing realSubject to a new RealSubject() in the constructor.

The instance variable realSubject should be set to null to delay creation.

4fill in blank

hard

Fill both blanks to add access control in Proxy before forwarding the request.

LLD

public void request() {
    if ([1]()) {
        realSubject.[2]();
    } else {
        System.out.println("Access denied.");
    }
}

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AcheckAccess

Brequest

Cvalidate

Dexecute

Attempts:

3 left

💡 Hint

Common Mistakes

Calling execute() instead of request() on realSubject.

Using validate() without defining it.

The Proxy checks access with checkAccess() before calling realSubject.request().

5fill in blank

hard

Fill all three blanks to implement caching in Proxy for the result of RealSubject's request.

LLD

private String cache;

public String request() {
    if (cache == null) {
        cache = realSubject.[1]();
    }
    return [2];
}

public void clearCache() {
    [3] = null;
}

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Aresult

Bcache

Drequest

Attempts:

3 left

💡 Hint

Common Mistakes

Returning realSubject.request() every time without caching.

Clearing the wrong variable in clearCache().

The Proxy caches the result of realSubject.request() in cache and returns it. clearCache() resets cache to null.