Creating the Class Diagram
One of the key components of low level design is creating the class diagram. The class diagram provides a visual representation of the classes and their relationships in the payment app.
To create the class diagram, we need to identify the classes that are part of the payment app and define their relationships. In this example, let's consider three main classes in the payment app: User, PaymentMethod, and Transaction.
1class User {
2 // class fields and methods
3}
4
5class PaymentMethod {
6 // class fields and methods
7}
8
9class Transaction {
10 // class fields and methods
11}In this class diagram, we have three classes: User, PaymentMethod, and Transaction. These classes represent the main entities in the payment app. Each class can have its own attributes and methods.
Next, we need to define the relationships between these classes. For example, a user can have multiple payment methods, so we can define a one-to-many relationship between the User and PaymentMethod classes:
1paymentApp.addRelationship("User", "PaymentMethod", "one-to-many");Similarly, a user can have multiple transactions, so we can define a one-to-many relationship between the User and Transaction classes:
1paymentApp.addRelationship("User", "Transaction", "one-to-many");Once we have defined the classes and their relationships, we can generate the class diagram using a class diagram generator. The generated class diagram provides a visual representation of the classes and their relationships in the payment app.
1ClassDiagramGenerator generator = new ClassDiagramGenerator();
2String classDiagram = generator.generate(paymentApp);Here's an example of a generated class diagram:
1Class Diagram:
2
3 +----------------+ +-------------------+
4 | User | <-------- | PaymentMethod |
5 +----------------+ +-------------------+
6 | | | |
7 | | | |
8 | | | |
9 +----------------+ +-------------------+
10 ^ |
11 | |
12 +-----+ |
13 | |
14 | |
15 V V
16+-----------------+ +----------------+
17| Transaction | | AnotherClass |
18+-----------------+ +----------------+xxxxxxxxxxclass Main { public static void main(String[] args) { // create an instance of a class PaymentApp paymentApp = new PaymentApp(); // add classes to the payment app paymentApp.addClass(new User()); paymentApp.addClass(new PaymentMethod()); paymentApp.addClass(new Transaction()); // create relationships between classes paymentApp.addRelationship("User", "PaymentMethod", "one-to-many"); paymentApp.addRelationship("User", "Transaction", "one-to-many"); // generate the class diagram ClassDiagramGenerator generator = new ClassDiagramGenerator(); String classDiagram = generator.generate(paymentApp); // print the class diagram System.out.println("Class Diagram:"); System.out.println(classDiagram); }}