Why low level design produces clean code in LLD - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a class with clear responsibilities.

LLD

class User [1]:
    def __init__(self, name):
        self.name = name

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

AManager

BEntity

CController

DService

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Controller' or 'Service' for a simple data class.

The class represents an entity with a clear responsibility, which helps keep code clean.

2fill in blank

medium

Complete the code to add a method that follows single responsibility principle.

LLD

class Calculator:
    def [1](self, a, b):
        return a + b

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

Aprocess

Bcalculate_sum

Csum

Dadd_numbers

Attempts:

3 left

💡 Hint

Common Mistakes

Using vague method names that do not describe the action.

The method name 'add_numbers' clearly describes its single responsibility, aiding clean code.

3fill in blank

hard

Fix the error in the method that violates clean code principles.

LLD

def process_data(data):
    result = []
    for item in data:
        if item > 0:
            result.append(item)
    return [1]

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

Aresult

Bitem

Cdata

DNone

Attempts:

3 left

💡 Hint

Common Mistakes

Returning the wrong variable or None.

The function should return the filtered list 'result' to keep code clean and functional.

4fill in blank

hard

Fill both blanks to create a clean function that separates concerns.

LLD

def [1](data):
    filtered = [x for x in data if x [2] 0]
    return filtered

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

Afilter_positive

B>

C<

Dprocess_data

Attempts:

3 left

💡 Hint

Common Mistakes

Using vague function names or wrong comparison operators.

The function name 'filter_positive' clearly states its purpose and uses '>' to filter positive numbers, following clean code principles.

5fill in blank

hard

Fill all three blanks to implement a clean class method that modifies state safely.

LLD

class Counter:
    def __init__(self):
        self.count = 0
    def [1](self):
        self.count [2] 1
        return self.[3]

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

Aincrement

B+=

Ccount

Dadd

Attempts:

3 left

💡 Hint

Common Mistakes

Using unclear method names or incorrect operators.

The method 'increment' clearly describes its action, uses '+=' to increase count, and returns the updated 'count' attribute, following clean code practices.

Practice

1. Why does low level design help produce clean code?

easy

A. It breaks the system into small, clear parts making code easier to understand.

B. It combines all code into one large block for simplicity.

C. It removes all comments to reduce clutter.

D. It uses complex logic to solve problems quickly.

Solution

1. Step 1: Understand low level design purpose

   Low level design divides a system into small, manageable components.

2. Step 2: Connect design to code clarity

   Smaller parts are easier to read, understand, and maintain, leading to clean code.

3. Final Answer:

   It breaks the system into small, clear parts making code easier to understand. -> Option A

4. Quick Check:

   Small parts = Clean code [OK]

Hint: Small clear parts mean clean, easy code [OK]

Common Mistakes:

• Thinking combining all code is simpler
• Believing removing comments cleans code
• Assuming complex logic makes code clean

2. Which of the following is a correct way to represent a class in low level design?

easy

A. function User() { this.name; this.age; }

B. User = { name, age, login }

C. class User { name; age; login() {} }

D. def User(name, age): pass

Solution

1. Step 1: Identify class syntax in low level design

   Low level design uses class diagrams or class-like structures to show attributes and methods clearly.

2. Step 2: Match syntax to class representation

   class User { name; age; login() {} } shows a class with attributes and a method, matching low level design style.

3. Final Answer:

   class User { name; age; login() {} } -> Option C

4. Quick Check:

   Class with attributes and methods = class User { name; age; login() {} } [OK]

Hint: Classes show attributes and methods clearly [OK]

Common Mistakes:

• Confusing object literals with class design
• Using function syntax instead of class
• Ignoring methods in class representation

3. Given this low level design snippet:

class Order {
  id;
  status;
  updateStatus(newStatus) {
    this.status = newStatus;
  }
}
let order = new Order();
order.updateStatus('shipped');
console.log(order.status);

What will be printed?

medium

A. undefined

B. null

C. error

D. shipped

Solution

1. Step 1: Analyze the updateStatus method call

   The method sets the status property of order to 'shipped'.

2. Step 2: Check the console.log output

   After updateStatus, order.status is 'shipped', so console.log prints 'shipped'.

3. Final Answer:

   shipped -> Option D

4. Quick Check:

   Method sets status = 'shipped' [OK]

Hint: Method sets property, so output matches new value [OK]

Common Mistakes:

• Assuming status is undefined without initialization
• Expecting null instead of updated value
• Thinking method call causes error

4. Identify the error in this low level design code snippet:

class Product {
  constructor(name) {
    this.name = name;
  }
  getName() {
    return name;
  }
}

medium

A. getName method returns undefined variable 'name' instead of this.name

B. Missing constructor keyword

C. Class name should be lowercase

D. Constructor should not have parameters

Solution

1. Step 1: Check getName method return statement

   It returns 'name' which is undefined in method scope; should use 'this.name'.

2. Step 2: Understand correct property access

   Class properties must be accessed with 'this' inside methods.

3. Final Answer:

   getName method returns undefined variable 'name' instead of this.name -> Option A

4. Quick Check:

   Use this.name to access property [OK]

Hint: Use this.property inside class methods [OK]

Common Mistakes:

• Ignoring 'this' keyword for properties
• Thinking constructor keyword is optional
• Believing class names must be lowercase

5. How does low level design improve maintainability in a large software project?

hard

A. By writing all code in one file to avoid confusion.

B. By splitting the system into small modules with clear responsibilities, making changes easier.

C. By removing all documentation to speed up coding.

D. By using complex nested functions to hide details.

Solution

1. Step 1: Understand maintainability needs

   Maintainability requires code to be easy to update and fix without breaking other parts.

2. Step 2: Connect low level design to maintainability

   Low level design breaks system into small modules with clear roles, so changes affect only small parts.

3. Step 3: Evaluate options

   Only By splitting the system into small modules with clear responsibilities, making changes easier. describes this modular approach; others increase complexity or confusion.

4. Final Answer:

   By splitting the system into small modules with clear responsibilities, making changes easier. -> Option B

5. Quick Check:

   Small modules = easier maintenance [OK]

Hint: Small modules with clear roles ease maintenance [OK]

Common Mistakes:

• Thinking one big file is easier to maintain
• Assuming no documentation helps speed
• Believing complex nesting hides problems