Mediator pattern in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the Mediator interface method for communication.

LLD

interface Mediator {
    void [1](String message, Colleague colleague);
}

Drag options to blanks, or click blank then click option'

Abroadcast

BreceiveMessage

CsendMessage

DnotifyAll

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'receiveMessage' instead of 'sendMessage'.

Using 'notifyAll' which is a Java Object method, not part of Mediator.

The Mediator interface typically defines a method like sendMessage to facilitate communication between colleagues.

2fill in blank

medium

Complete the code to implement the colleague's method to send a message via the mediator.

LLD

class ConcreteColleague extends Colleague {
    void send(String message) {
        mediator.[1](message, this);
    }
}

Drag options to blanks, or click blank then click option'

AsendMessage

BreceiveMessage

Cnotify

DbroadcastMessage

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a method named 'receiveMessage' on the mediator.

Using 'notify' which is unrelated here.

The colleague uses the mediator's sendMessage method to send messages.

3fill in blank

hard

Fix the error in the mediator's notify method to correctly notify all colleagues except the sender.

LLD

void notifyColleagues(String message, Colleague sender) {
    for (Colleague colleague : colleagues) {
        if (colleague != [1]) {
            colleague.receive(message);
        }
    }
}

Drag options to blanks, or click blank then click option'

Athis

Bsender

Cnull

Dcolleague

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'this' which refers to the mediator itself.

Using 'colleague' which is the loop variable.

The mediator should skip notifying the sender, so it compares with the sender parameter.

4fill in blank

hard

Fill both blanks to define a colleague class constructor and store the mediator reference.

LLD

class ConcreteColleague extends Colleague {
    ConcreteColleague(Mediator [1]) {
        this.[2] = [1];
    }
}

Drag options to blanks, or click blank then click option'

Amediator

Bcolleague

CmediatorRef

Dsender

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for parameter and instance variable causing confusion.

Using unrelated names like 'colleague' or 'sender'.

The constructor parameter and the instance variable are both commonly named mediator to hold the mediator reference.

5fill in blank

hard

Fill all three blanks to implement the mediator's sendMessage method that forwards messages to all colleagues except the sender.

LLD

void [1](String message, Colleague sender) {
    for (Colleague [2] : colleagues) {
        if ([2] != sender) {
            [2].receive(message);
        }
    }
}

Drag options to blanks, or click blank then click option'

AsendMessage

Bcolleague

Cnotify

Dbroadcast

Attempts:

3 left

💡 Hint

Common Mistakes

Using different variable names inconsistently.

Using incorrect method names like 'notify' or 'broadcast'.

The method name is sendMessage. The loop variable is colleague, used twice to check and call receive.