Designing Classes and Objects

In low level design, the process of designing classes and objects plays a crucial role in creating a well-structured and efficient system. Classes in low level design represent the blueprints or templates for objects, while objects are instances of those classes.

When designing classes and objects, it is important to consider the following aspects:

1. Responsibilities: Each class should have a clear set of responsibilities and should represent a single entity or concept in the system. For example, in a banking system, we can have classes like Account, Transaction, and Customer.

2. Attributes: Classes have attributes that represent the state or data associated with the objects. Attributes can be defined as properties or variables within a class. For example, the Account class can have attributes like accountNumber, balance, and customerName.

3. Methods: Methods define the behavior or actions that objects of a class can perform. They encapsulate the logic and functionality related to the class. For example, the Account class can have methods like deposit(amount), withdraw(amount), and getBalance().

4. Relationships: Classes can have relationships with each other, such as associations, aggregations, or inheritances. These relationships define how objects interact with each other and can be represented using UML diagrams. For example, the Customer class can have an aggregation relationship with the Account class.

Here's an example of designing a Car class:

1// Car class
2public class Car {
3  // Attributes
4  private String color;
5  private String brand;
6  private String model;
7
8  // Constructor
9  public Car(String color, String brand, String model) {
10    this.color = color;
11    this.brand = brand;
12    this.model = model;
13  }
14
15  // Getters and Setters
16  public String getColor() {
17    return color;
18  }
19
20  public void setColor(String color) {
21    this.color = color;
22  }
23
24  public String getBrand() {
25    return brand;
26  }
27
28  public void setBrand(String brand) {
29    this.brand = brand;
30  }
31
32  public String getModel() {
33    return model;
34  }
35
36  public void setModel(String model) {
37    this.model = model;
38  }
39
40  // Other methods
41  public void start() {
42    // Add logic to start the car
43  }
44
45  public void accelerate() {
46    // Add logic to accelerate the car
47  }
48
49  public void stop() {
50    // Add logic to stop the car
51  }
52}

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}

class Car {

  private String color;

  private String brand;

  private String model;

​

  public Car(String color, String brand, String model) {

    this.color = color;

    this.brand = brand;

    this.model = model;

  }

​

  public String getColor() {

    return color;

  }

​

  public void setColor(String color) {

    this.color = color;

  }

​

  public String getBrand() {

    return brand;

  }

​

  public void setBrand(String brand) {

    this.brand = brand;

  }

​

  public String getModel() {

    return model;