LAB Java | System Design

Introduction

We have just learned how to use Enums and HashMaps and create Use Case and UML class diagrams so let's practice a bit more.

Requirements

1. Fork this repo.
2. Clone this repo.
3. Add your instructor and the class graders as collaborators to your repository. If you are unsure who your class graders are, ask your instructor or refer to the day 1 slide deck.
4. In the repository, create a Java project and add the code for the following prompts.

Submission

Once you finish the assignment, submit a URL link to your repository or your pull request in the field below.

Instructions

1. Create a new Java project in your preferred development environment.
2. In the project, create a class called Student that contains the following properties:
   • name: String
   • grade: int (in the range 0-100)
3. Create a Map with a key of the student's name (String) and a value of a Student object.
4. Create a method called increaseGrades that takes a Map<String, Student> as a parameter, increases every student's grade by 10% and returns the updated map.
5. Create 4 Student objects for your classmates and add them to the Map.
6. Create a use case diagram and a class diagram for an online banking system. The system should have the following features:
   • Users can transfer funds, withdraw from their accounts and deposit to their accounts.
   • Admins can freeze accounts in the event of fraud.
   • Use the Money class in your class diagram.

FAQs

I am stuck and don't know how to solve the problem or where to start. What should I do?

If you are stuck in your code and don't know how to solve the problem or where to start, you should take a step back and try to form a clear, straight forward question about the specific issue you are facing. The process you will go through while trying to define this question, will help you narrow down the problem and come up with potential solutions.

For example, are you facing a problem because you don't understand the concept or are you receiving an error message that you don't know how to fix? It is usually helpful to try to state the problem as clearly as possible, including any error messages you are receiving. This can help you communicate the issue to others and potentially get help from classmates or online resources.

Once you have a clear understanding of the problem, you should be able to start working toward the solution.

How do I create a Maven project in IntelliJ?

To create a Maven project in IntelliJ, you can follow these steps:

1. Open IntelliJ IDEA and click the "Create New Project" button.
2. In the "New Project" dialog, select "Maven" as the build system.
3. Specify the name of the project.
4. In the "Project Location" section, specify a location where you want to save your project.
5. Select the "Create Git repository" checkbox in order to initialize the git repository upon creation of the project.
6. Click the "Create" button to create the Maven project.

How do I use "HashMaps" in Java and how can I print them?

A HashMap in Java is a data structure that stores key-value pairs. It is implemented as an unordered map, meaning that the order of the elements may change over time.

Here's an example of how you can create and use a HashMap in Java:

import java.util.HashMap;

public class Main {
    public static void main(String[] args) {
        HashMap<String, Integer> map = new HashMap<>();
        map.put("Key 1", 1);
        map.put("Key 2", 2);
        map.put("Key 3", 3);

        System.out.println("Value of Key 1: " + map.get("Key 1"));
        System.out.println("Value of Key 2: " + map.get("Key 2"));
        System.out.println("Value of Key 3: " + map.get("Key 3"));
    }
}

In the example above, we first create a HashMap map that stores String keys and Integer values. We then use the put method to add three key-value pairs to the map. Finally, we use the get method to retrieve and print the values associated with each key.

To print the entire HashMap, you can use a forEach loop:

map.forEach((key, value) -> System.out.println("Key: " + key + ", Value: " + value));

In this example, the forEach loop iterates over each key-value pair in the HashMap and prints the key and value.

What is the purpose of a use case diagram in software development and how is it created?

A use case diagram is a graphical representation of the interactions between a system and its users, also known as actors. It is used in software development to describe the functional requirements of a system. The purpose of a use case diagram is to provide a clear and concise view of the system's requirements and to help stakeholders understand the interactions between the system and its users.

A use case diagram is created by identifying the actors, or users, of the system and their interactions with the system. The interactions are represented as use cases, which are graphical representations of a specific task or goal that the user wants to accomplish.

To create a use case diagram, you will need a software development tool that supports UML (Unified Modeling Language) diagrams. You will also need to define the system's boundaries and identify the actors that interact with the system.

Here is an example of how to create a use case diagram in a UML modeling tool:

1. Start by defining the system boundaries and identifying the actors.
2. Create use cases for each interaction between the actors and the system.
3. Connect the actors to the use cases using lines to represent the interactions.
4. Label each use case with a clear and concise description of the interaction.
5. Review the diagram to ensure that it accurately represents the system's requirements and the interactions between the actors and the system.

Note: This is a basic example and the steps to create a use case diagram may vary depending on the tool you are using.

What is the purpose of a "class diagram" in software development and how is it created?

A class diagram in software development is a visual representation of the classes, attributes and methods in a software system. It is used to show the relationships between objects and classes.

In a class diagram, classes are represented by rectangles and are labeled with their names. Attributes of the class are represented by "oval" shapes with their names inside and are labeled with either a "+" symbol for "public" attributes, a "-" symbol for "private" attributes, or a "#" symbol for "protected" attributes. Methods of the class are represented by "oval" shapes with their names inside and are labeled with either a "+" symbol for "public" methods, a "-" symbol for "private" methods, or a "#" symbol for "protected" methods.

The class diagram is a useful tool for developers as it provides a clear and concise view of the structure of the software system and helps to identify any potential problems early in the development process.

I am unable to push changes to my repository. What should I do?

If you are unable to push changes to your repository, here are a few steps that you can follow:

1. Check your internet connection: Ensure that your internet connection is stable and working.
2. Verify your repository URL: Make sure that you are using the correct repository URL to push your changes.
3. Check Git credentials: Ensure that your Git credentials are up-to-date and correct. You can check your credentials using the following command:

git config --list

4. Update your local repository: Before pushing changes, make sure that your local repository is up-to-date with the remote repository. You can update your local repository using the following command:

git fetch origin

5. Check for conflicts: If there are any conflicts between your local repository and the remote repository, resolve them before pushing changes.
6. Push changes: Once you have resolved any conflicts and updated your local repository, you can try pushing changes again using the following command:

git push origin <branch_name>