Introduction to LOW level design

Low level design is a crucial aspect of software development. It focuses on the implementation details of a system or application, such as algorithms, data structures, and database schema. In low level design, we dive deep into the technical aspects to ensure efficient and optimized code.

Low level design plays a vital role in building scalable and maintainable software solutions. It helps in identifying potential bottlenecks, performance optimizations, and resource management. By considering low level design principles, we can create robust and high-performing applications.

As a senior engineer with a strong background in Java development, Spring Boot, MySQL, and AWS, you already have a solid foundation in software development. Low level design will further enhance your skills by providing you with a deeper understanding of the internal workings of a system.

To give you a taste of low level design in action, let's take a look at a simple example. The following Java code demonstrates the classic 'FizzBuzz' problem:

1class Main {
2  public static void main(String[] args) {
3    for(int i = 1; i <= 100; i++) {
4      if(i % 3 == 0 && i % 5 == 0) {
5          System.out.println("FizzBuzz");
6      } else if(i % 3 == 0) {
7          System.out.println("Fizz");
8      } else if(i % 5 == 0) {
9          System.out.println("Buzz");
10      } else {
11          System.out.println(i);
12      }
13    }
14  }
15}

In this code, we iterate from 1 to 100 and print 'Fizz' if the number is divisible by 3, 'Buzz' if it's divisible by 5, and 'FizzBuzz' if it's divisible by both 3 and 5. Otherwise, we print the number itself. This simple example showcases the logical thinking and implementation details involved in low level design.

Throughout this course on low level design, we will explore various topics such as problem statement analysis, requirements identification, class diagram creation, entity-relationship mapping, database schema design, design patterns, and implementing code in Java. By the end of the course, you will have a solid understanding of low level design principles and how to apply them in real-world scenarios.

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class Main {

  public static void main(String[] args) {

    // replace with your Java logic here

    for(int i = 1; i <= 100; i++) {

      if(i % 3 == 0 && i % 5 == 0) {

          System.out.println("FizzBuzz");

      } else if(i % 3 == 0) {

          System.out.println("Fizz");

      } else if(i % 5 == 0) {

          System.out.println("Buzz");

      } else {

          System.out.println(i);

      }

    }

  }

}

Understanding Problem Statements

As a senior engineer with a strong background in Java development, Spring Boot, MySQL, and AWS, you already have a solid foundation in software development. Now, let's dive into the world of low level design and explore the process of analyzing problem statements and identifying requirements for design.

When it comes to low level design, the first step is to understand the problem at hand. This involves carefully examining the problem statement, understanding the desired functionality and constraints, and identifying the key requirements.

Let's consider an example of a payment app. As the senior engineer responsible for designing the low level architecture of the app, you need to analyze the problem statement and determine the requirements.

The problem statement might include information such as:

• The payment app should allow users to make online payments securely.
• The app should support multiple payment methods, such as credit cards, debit cards, and digital wallets.
• Users should be able to view their transaction history and manage their payment methods.

Once you have analyzed the problem statement, you can start identifying the key requirements. These requirements will shape the design of your payment app. For example:

1. Secure Authentication: The app should provide a secure login mechanism to protect user accounts and prevent unauthorized access.
2. Payment Integration: The app should integrate with payment gateways to process transactions and handle different payment methods.
3. Transaction History: The app should store and display transaction history for users to review past payments.

By analyzing the problem statement and identifying the requirements, you can gain a clear understanding of what needs to be implemented in your low level design.

1class PaymentApp {
2  public static void main(String[] args) {
3    // Replace with your code here
4    System.out.println("Welcome to the Payment App!");
5  }
6}

In the provided Java code snippet, we have a simple PaymentApp class with a main method. This acts as the starting point of our payment app. As the design progresses, you will be filling in this code with the actual implementation.

Now that you have a high-level understanding of the problem statement and requirements, it's time to move on to the next step in low level design: creating class diagrams. Class diagrams provide a visual representation of the relationships between objects and help you define the structure of your application.

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class PaymentApp {

  public static void main(String[] args) {

    // Replace with your code here

    System.out.println("Welcome to the Payment App!");

  }

}

Creating Class Diagrams

Class diagrams are a visual representation of the relationships between objects in a system. They help us understand the structure and behavior of the classes that make up our application.

Let's consider the example of a car rental system. In this system, we have two main classes: "Car" and "Person". The class diagram for this system would look like this:

In this diagram, we can see that the "Person" class has an association with the "Car" class. This means that a person can have a car. The association is represented by a line connecting the two classes, with an arrow pointing to the "Car" class.

The diagram also shows the properties of each class. The "Car" class has three properties: "brand", "color", and "year". The "Person" class has two properties: "name" and "age".

To create a class diagram, we start by identifying the classes in our system and their relationships. We then represent these classes and relationships using appropriate symbols and notations.

Class diagrams are an important tool in low level design as they provide a visual representation of the system's structure. They help us understand how the classes in our system interact with each other and how data is transferred between them.

1  class Main {
2    public static void main(String[] args) {
3    // replace with your Java logic here
4    
5    // Define the classes
6    class Car {
7      String brand;
8      String color;
9      int year;
10    }
11    
12    class Person {
13      String name;
14      int age;
15      Car car;
16    }
17    
18    // Create objects
19    Car myCar = new Car();
20    myCar.brand = "Toyota";
21    myCar.color = "Red";
22    myCar.year = 2022;
23    
24    Person person = new Person();
25    person.name = "John";
26    person.age = 25;
27    person.car = myCar;
28    
29    // Print information
30    System.out.println("Person: " + person.name);
31    System.out.println("Age: " + person.age);
32    System.out.println("Car: " + person.car.brand + " " + person.car.color + " " + person.car.year);
33    }
34  }

In the provided Java code snippet, we have defined two classes: "Car" and "Person". We then create objects of these classes and demonstrate how they are related. The code creates a "Person" object with a name, age, and a reference to a "Car" object. We then print out the information of the person and the car.

Class diagrams are a powerful tool for visualizing and understanding the relationships between objects in a system. By creating class diagrams, we can better design and communicate the structure of our low level systems.

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  }

class Main {

    public static void main(String[] args) {

    // replace with your Java logic here

    // Define the classes

    class Car {

      String brand;

      String color;

      int year;

    }

    class Person {

      String name;

      int age;

      Car car;

    }

    // Create objects

    Car myCar = new Car();

    myCar.brand = "Toyota";

    myCar.color = "Red";

    myCar.year = 2022;

    Person person = new Person();

    person.name = "John";

    person.age = 25;

    person.car = myCar;

    // Print information

Entity-Relationship Mapping

In low level design, entity-relationship mapping is a crucial step that involves mapping objects from our system to database entities and establishing relationships between these entities. By mapping objects to database entities, we can effectively store and retrieve data in a structured manner.

To understand entity-relationship mapping, let's use an example related to a payment application.

Consider the following entities in our payment application:

• User: Represents a user of the application and has attributes such as user_id, name, and email.
• Account: Represents a user's account and has attributes such as account_id, user_id (foreign key), and balance.
• Transaction: Represents a transaction made by a user and has attributes such as transaction_id, account_id (foreign key), amount, and timestamp.

To establish relationships between these entities, we can use foreign keys. In our example, the user_id attribute in the Account entity is a foreign key that references the user_id attribute in the User entity. Similarly, the account_id attribute in the Transaction entity is a foreign key that references the account_id attribute in the Account entity.

By establishing these relationships, we can create a logical connection between the entities in our database. For example, we can retrieve all transactions made by a specific user by joining the User, Account, and Transaction tables using the foreign keys.

Let's take a look at an example of entity-relationship mapping using Java code:

1class User {
2  int user_id;
3  String name;
4  String email;
5}
6
7class Account {
8  int account_id;
9  int user_id;
10  double balance;
11}
12
13class Transaction {
14  int transaction_id;
15  int account_id;
16  double amount;
17  Date timestamp;
18}
19
20// Create a user
21User user = new User();
22user.user_id = 1;
23user.name = "John Doe";
24user.email = "john@example.com";
25
26// Create an account
27Account account = new Account();
28account.account_id = 1;
29account.user_id = user.user_id;
30account.balance = 1000.0;
31
32// Create a transaction
33Transaction transaction = new Transaction();
34transaction.transaction_id = 1;
35transaction.account_id = account.account_id;
36transaction.amount = 50.0;
37transaction.timestamp = new Date();

Database Schema Design

Database schema design is a critical step in low-level design that involves designing the structure and organization of a database based on the entity-relationship mapping. It determines how data will be stored, how entities will be related to each other, and how queries will be executed efficiently.

When designing a database schema, it is important to consider the performance, scalability, and integrity of the database. This includes determining the appropriate data types for each attribute, defining primary and foreign key constraints, and establishing relationships between entities.

To illustrate the process of database schema design, let's continue with our payment application example. Based on the entity-relationship mapping we defined earlier, we can design the following database schema:

• User table

  • user_id (Primary key)
  • name
  • email

• Account table

  • account_id (Primary key)
  • user_id (Foreign key referencing User.user_id)
  • balance

• Transaction table

  • transaction_id (Primary key)
  • account_id (Foreign key referencing Account.account_id)
  • amount
  • timestamp

The above database schema represents the entities defined in our payment application and their relationships. It allows us to store and retrieve user information, account details, and transaction data efficiently.

In Java, we can create classes that represent the entities in our database schema. Here's an example:

1class User {
2  int user_id;
3  String name;
4  String email;
5}
6
7class Account {
8  int account_id;
9  int user_id;
10  double balance;
11}
12
13class Transaction {
14  int transaction_id;
15  int account_id;
16  double amount;
17  Date timestamp;
18}

In the main method of a Java program, we can write the logic related to database schema design, such as creating tables, defining constraints, and establishing relationships.

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class Main {

  public static void main(String[] args) {

    // Replace with your Java logic

    // related to database schema design

  }

}

Design Patterns in LOW level design

Design patterns are common solutions to recurring design problems in software development. They provide a structured approach to solving design problems and promote code reusability, maintainability, and scalability.

In low-level design, there are several design patterns that are commonly used to address specific design challenges. Let's explore some of the design patterns used in low-level design and their applications:

1. Singleton Design Pattern

The Singleton design pattern ensures that a class has only one instance and provides a global point of access to it. This pattern is often used in low-level design when you need to restrict the instantiation of a class to a single object. It is commonly used for managing shared resources, such as database connections or thread pools.

Here's an example of implementing the Singleton design pattern in Java:

1public class Singleton {
2  private static Singleton instance;
3
4  private Singleton() {
5    // Constructor logic
6  }
7
8  public static Singleton getInstance() {
9    if (instance == null) {
10      instance = new Singleton();
11    }
12    return instance;
13  }
14}

In the main method of a Java program, you can utilize the Singleton class as follows:

1public static void main(String[] args) {
2  Singleton singleton = Singleton.getInstance();
3}

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class Main {

  public static void main(String[] args) {

    // Replace with your Java logic here

    System.out.println("Singleton Design Pattern");

  }

}

Implementing Code in Java

Now that we have learned about the low-level design concepts and the steps involved in designing a database schema, let's explore how to implement these concepts in Java.

Java is a popular programming language known for its robustness and scalability. It is widely used in enterprise-level applications and provides excellent support for building low-level designs.

In this section, we will demonstrate the implementation of the low-level design concepts using Java programming language.

As an example, let's consider the classic FizzBuzz problem. The FizzBuzz problem is a common coding interview question where you have to print numbers from 1 to 100, but for multiples of 3, you print "Fizz", for multiples of 5, you print "Buzz", and for numbers that are multiples of both 3 and 5, you print "FizzBuzz".

Here is the Java code to solve the FizzBuzz problem:

1class Main {
2  public static void main(String[] args) {
3    for(int i = 1; i <= 100; i++) {
4      if(i % 3 == 0 && i % 5 == 0) {
5          System.out.println("FizzBuzz");
6      } else if(i % 3 == 0) {
7          System.out.println("Fizz");
8      } else if(i % 5 == 0) {
9          System.out.println("Buzz");
10      } else {
11          System.out.println(i);
12      }
13    }
14  }
15}

You can execute this code in any Java IDE or compile it using the command-line Java compiler and run the generated bytecode.

By implementing the low-level design concepts in Java, we can create scalable and efficient solutions for various software applications.

Now that you have seen an example of implementing code in Java, you can further explore different low-level design concepts and try implementing them in Java.

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class Main {

    public static void main(String[] args) {

    // replace with your Java logic here

    for(int i = 1; i <= 100; i++) {

      if(i % 3 == 0 && i % 5 == 0) {

          System.out.println("FizzBuzz");

      } else if(i % 3 == 0) {

          System.out.println("Fizz");

      } else if(i % 5 == 0) {

          System.out.println("Buzz");

      } else {

          System.out.println(i);

      }

    }    

  }

}