Law of Demeter in LLD - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to follow the Law of Demeter by accessing only immediate friends.

LLD

class Car {
    Engine engine;
    void start() {
        engine.[1]();
    }
}

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AgetFuel

BgetPistons

CgetOilLevel

Dignite

Attempts:

3 left

💡 Hint

Common Mistakes

Calling methods on objects returned by other methods (chained calls).

The method ignite is a direct action on the immediate friend engine, following the Law of Demeter.

2fill in blank

medium

Complete the code to avoid violating the Law of Demeter by not accessing nested objects directly.

LLD

class Library {
    Book book;
    void printAuthor() {
        System.out.println(book.[1]());
    }
}

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AgetPublisher

BgetTitle

CgetAuthor

DgetYear

Attempts:

3 left

💡 Hint

Common Mistakes

Calling methods on objects returned by getPublisher() or deeper.

Accessing getAuthor() is allowed because book is a direct friend. Accessing nested objects beyond that would violate the Law of Demeter.

3fill in blank

hard

Fix the error in the code to comply with the Law of Demeter by removing chained calls.

LLD

class Computer {
    CPU cpu;
    void checkStatus() {
        cpu.[1]();
    }
}

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Astart

BgetSpeed

CgetFan

DgetCache

Attempts:

3 left

💡 Hint

Common Mistakes

Using chained calls like cpu.getFan().getTemperature().

Calling start() on cpu is allowed as it is a direct friend. Calling getFan() returns another object, leading to chained calls which violate the Law of Demeter.

4fill in blank

hard

Fill both blanks to rewrite the code so it respects the Law of Demeter by delegating calls.

LLD

class House {
    Kitchen kitchen;
    void clean() {
        kitchen.[1]();
        kitchen.[2]();
    }
}

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AcleanSink

BgetFridge

CcleanFloor

DgetOven

Attempts:

3 left

💡 Hint

Common Mistakes

Calling methods on nested objects like getFridge() or getOven().

Calling cleanSink() and cleanFloor() directly on kitchen respects the Law of Demeter by avoiding chained calls.

5fill in blank

hard

Fill all three blanks to refactor the code to follow the Law of Demeter by avoiding chained calls.

LLD

class School {
    Classroom classroom;
    void startClass() {
        classroom.[1]();
        classroom.[2]().[3]();
    }
}

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AopenDoor

BgetTeacher

CteachLesson

DgetStudents

Attempts:

3 left

💡 Hint

Common Mistakes

Calling methods on objects returned by getStudents() or chaining deeper than one level.

Calling openDoor() directly on classroom and then calling teachLesson() on the teacher obtained via getTeacher() respects the Law of Demeter by limiting access to immediate friends.