Java 2

Week 1

Topics

UML Class Diagrams
Classes and Objects
Collections (List and ArrayList)
GitHub Setup

What is UML?

UML is the “Unified Modeling Language”
Standard modeling language for software development
Maintained by Object Management Group
Made up of pseudo-code, notations, pictures, diagrams, etc
Describes the system we want to develop

UML Textbook

The UML textbook is optional for this class, but may be required for other classes.
- If you have a copy of the UML textbook, today's lesson covers Modules 3 and 6.
- If you don't have a copy of the UML textbook, consider reading tutorials like these:
  - https://agilemodeling.com/artifacts/classdiagram.htm
  - https://developer.ibm.com/articles/the-class-diagram/

Class Diagrams

Class diagrams show the classes of the system, their relationships, and the attributes and operations (methods).
Classes form the main building blocks of an object-oriented application.

User
- userId : int - firstName : String - lastName : String
+ getUserId() : int + setUserId(int) : void + getFirstName() : String + setFirstName(String) : void + getLastName() : String + setLastName(String) : void + toString() : String

Three Boxes

Classes are depicted as boxes with three sections:
- The top box indicates the name of the class. The name is typically a singular noun. Class names should always start with a capital letter.
- The middle box lists the attributes of the class - the information stored about an object
- The bottom box lists the methods - the operations an object or class do.

Name
- attributes
+ methods

Access Modifiers

The + symbol represents a public access modifier, meaning all other classes have access.
The - symbol represents a private access modifier, meaning only the current class has access.
The / symbol (not shown) represents a derived modifier - a value not stored but is calculated from other attributes when needed
- For example, GPA could be derived from a list of grades
The # symbol (not shown) represents a protected access modifier, meaning other classes in the same package has access to the attribute.

User
- userId : int - firstName : String - lastName : String
+ getUserId() : int + setUserId(int) : void + getFirstName() : String + setFirstName(String) : void + getLastName() : String + setLastName(String) : void + toString() : String

Data Types, Parameters, Return

Attribute data types are shown after a colon.
Method parameters are shown inside parentheses.
- Getter methods and the toString method have no parameters.
- Setter method parameters will typically match the attribute data type.
Method return types are shown after the colon.
- Getter methods will always return the attribute data type.
- Setter methods will always return void.
- The toString method will always return a String.

User
- userId : int - firstName : String - lastName : String
+ getUserId() : int + setUserId(int) : void + getFirstName() : String + setFirstName(String) : void + getLastName() : String + setLastName(String) : void + toString() : String

Inheritance

Inheritance is a mechanism to prevent writing repeated code.
Inheritance models “is a” relationships, enabling you to reuse existing attributes and methods easily.
When A inherits from B, we say A is the subclass of B, and B is the superclass of A.
The notation for inheritance is a line with an open arrowhead pointing from the subclass to the superclass.

Professor
- salary : double
+ getSalary(): double + setSalary(double): void + toString(): String

Student
- gradeLevel : int - gpa : double
+ getGradeLevel(): int + setGradeLevel(int): void + getGpa(): int + setGpa(int): void + toString(): String

User
- userId : int - firstName : String - lastName : String
+ getUserId : int + setUserId : void + getFirstName : String + setFirstName : void + getLastName : String + setLastName : void + toString : String

is a

Associations

Objects are often associated with other objects.
For example:
- A professor instructs a course
- A student enrolls in a course
- A course has enrollments
Associations are modeled as lines connecting the two classes.
Associations can be clarified by depicting labels and directionality.

Enrollment
- student : Student - course : Course - finalGrade : char
+ getStudent(): Student + setStudent(Student): void + getSection(): Section + setSection(Section): void + getFinalGrade(): char + setFinalGrade(char): void + toString()

Course
- courseId : int - title: String - featured: boolean
+ getCourseId(): int + setCourseId(int): void + getTitle(): String + setTitle(String): void + isFeatured(): boolean + setFeatured(boolean): void + toString(): String

instructs

has

Professor

Student

User

Composition Associations

If it makes sense to say something is part of (or consists of) something else, then you should use composition (aka aggregation).
Composite associations are shown with a diamond.
For example, it makes sense to say that:
- Enrollment is on a grade report -or- a grade report is composed of enrollments.
- A room is part of a building -or- a building is composed of rooms.

Enrollment

Student

GradeReport
- student : Student - enrollments : List<Enrollment> - dateCreated : LocalDate
// methods omitted

receives

composed of

has

Association Multiplicity

The multiplicity of the association is labeled on either end of the line, one multiplicity indicator for each direction
Each student has 0 or more enrollments.
- Each enrollment has 1 student.
Each professor instructs 0 to 5 courses.
- Each course has 1 to 3 professors.

Indicator	Meaning
0..1	Zero or one
0..*	Zero or more
0..n (such as 0..10)	Zero to n (such as zero to ten)
n (such as 1)	Exactly n (Only one)
1..*	One or more
1..n (such as 1..10)	One to n (such as one to ten)

Enrollment

Course

Professor

Student

User

1

0..*

0..6

1..3

1

0..*

Each course has 0 or more enrollments.
Each enrollment has 1 course.

UML Diagramming Tools

Week 1 Lab

Your Task:

With the direction of the teacher, create a complete class diagram using one of the tools above.
Download the final example for Diagrams.net

Week 1 Assignment

An administrator updates the product catalog. Each product has a product id, vendor id, name, price, and description.
Each product may be purchased from one or more vendors. Each vendor has an id, name, and address (city, state, zip, country).
A customer can place an order by submitting a form. The order form collects the customer's name, address (city, state, zip, country), phone number, and email address.
Each order has an id, date, and customer id. An order consists of one or more order items.
Each order item is associated with an order and a product. It also contains the quantity sold and price.

Your Task:

Identify six nouns from the problem domain above that can be used as classes.
Use a diagramming tool to create a class diagram with access modifiers, data types, parameters, return types, inheritance, associations, composition, multiplicity, and annotations.

New Java Project

Create a new Java Maven project using VS Code. Call the project "java2-demos". Use "edu.kirkwood" as the groupId.
- Companies often declare packages starting with their website domain written backwards.
- We will use VS Code to prepare you for a state Java programming competition in Des Moines next February.
- We will eventually use JetBrains IntelliJ to build a web application using the code we are writing today.
In the root folder, create a .gitignore file. Add this to ignore compiled class files
*.class
Inside the "edu.kirkwood" package, create a new package called "learnx".
Inside the "learnx" package, create a new package called "model", "controller", and "data". We will create a "view" package later.

LearnxUser Class

In the model package, create the User class with these attributes.
- userId : int
- firstName : String
- lastName : String
Generate default and parameterized constructors, getter and setter methods, and a toString method.

package edu.kirkwood.learnx.model;

public class LearnxUser {
    private int userId;
    private String firstName;
    private String lastName;
    
    public LearnxUser() {}

    public LearnxUser(int userId, String firstName, String lastName) {
        this.userId = userId;
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public int getUserId() {
        return userId;
    }

    public void setUserId(int userId) {
        this.userId = userId;
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    @Override
    public String toString() {
        return "LearnxUser [userId=" + userId + ", firstName=" + firstName + ", lastName="
                + lastName + "]";
    }

}

Student Class

In the model package, create the Student class that inherits User, with these attributes.
- gradeLevel : int
- gpa : double
Generate default and parameterized constructors, getter and setter methods, and a toString method.

package edu.kirkwood.learnx.model;

public class Student extends LearnxUser {
    private int gradeLevel;
    private double gpa;

    public Student() {
        super();
    }

    public Student(int userId, String firstName, String lastName, int gradeLevel, double gpa) {
        super(userId, firstName, lastName);
        this.gradeLevel = gradeLevel;
        this.gpa = gpa;
    }

    public int getGradeLevel() {
        return gradeLevel;
    }

    public void setGradeLevel(int gradeLevel) {
        this.gradeLevel = gradeLevel;
    }

    public double getGpa() {
        return gpa;
    }

    public void setGpa(double gpa) {
        this.gpa = gpa;
    }

    @Override
    public String toString() {
    	return "Student [userId=" + getUserId() + ", firstName=" + getFirstName() + ", lastName="
                + getLastName() + ", gradeLevel=" + gradeLevel + ", gpa=" + gpa + "]";
    }

    

    
}

StudentDAO Class

In the data package, Create a StudentDAO (data access object) class that will be used to create Student objects.
Create a method called getSampleStudents that returns a List of two Students.

package edu.kirkwood.learnx.data;

import java.util.ArrayList;
import java.util.List;
import edu.kirkwood.learnx.model.Student;

public class StudentDAO {
    public static List<Student> getSampleStudents() {
        List<Student> students = new ArrayList<>();
        students.add(new Student());
        students.add(new Student(1, "Marc", "Hauschildt", 12, 3.65));
        return students;
    }
}

SeatingChartBuilder Class

In the controller package, create a SeatingChartBuilder class with a main method that calls the getSampleStudents method and prints the two Student objects.

package edu.kirkwood.learnx;

import java.util.List;
import edu.kirkwood.learnx.data.StudentDAO;
import edu.kirkwood.learnx.model.Student;

public class SeatingChartBuilder {
    public static void main(String[] args) {
        List<Student> students = StudentDAO.getSampleStudents();
        for(Student student: students) {
            System.out.println(student);
        }
    }
}

Git Setup

Open the "java2-demos" folder in VS Code. Make sure the "src", folder is visible.
Click the "Terminal" menu and select "New Terminal". Click the arrow next to the "+" button. Choose "Select Default Profile". Select Git Bash. Click the trash can icon to close the terminal.
Click the "Source Control" button on the left taskbar.
Click the blue "Initialize Repository" button.
- Alternatively, open a new Terminal and enter this command:
  git init -b main
- If the task bar at the bottom-left displays "master" instead of "main", run this command:
  git checkout -b main

Git Setup

The panel will indicate that there are several uncommitted changes. Hold your mouse over the word "Changes" to see 3 new buttons "View Changes", "Discard All Changes", and "Stage All Changes". Click "Stage All Changes".
- Alternatively, enter this command in the terminal.
  git add .
- Note that you can also add files individually.
Type the message "initial commit" and press the blue "Commit" button.
- Make sure you have added your name and email with these terminal commands.
  git config --global user.name "YOUR FULL NAME" git config --global user.email "YOUR EMAIL ADDRESS"
- Alternatively, enter this command
  git commit -m "initial commit"

Git Setup

Click the blue "Publish Branch" button.
The first time you do this you will need to sign into GitHub.
- Windows Users: Sign in with your GitHub password.
- Mac Users: When signing in with your GitHub password, you may get an error saying you need to use a personal access token. See the next slide for instructions.
Click "Publish to GitHub private repository".
Alternatively, manually create a private "java2-demos" repository, then enter these commands in the terminal:
git remote add origin https://github.com/YOUR-USERNAME/java2-demos.git git push origin main

Mac Users

Click "Log In with Token".
Click "Generate".
Log in to your GitHub account.
You will be on a screen to generate a new personal access token. The note should be pre-filled with "IntelliJ IDEA GitHub integration plugin".
Set the expiration date to be after the semester ends (or Never).
Select the Repo check box.
Click Generate Token and copy the token that is generated.
Paste the token as the password in the IntelliJ GitHub popup.
In the Terminal app, enter this command so you only have to enter the token once.
git config --global credential.helper cache

Git Setup

View your GitHub repository page to see the changes.
As we advance, commit regularly. Please change commit messages each time to something short and descriptive. Only push to GitHub when your work is ready to grade.
Student To-do:
- Click the "Settings" tab.
- Choose Access > Collaborators, and click "Add people".
- Type "mlhaus" and select the instructor's profile. The instructor will grade all assignments via GitHub.
Instructor To-do:
- Click the "Settings" tab, then set the visibility to public so students can access it.
- Copy and paste a link to the course content so students always have access to demo code.

Git Setup

Note the tab in the menu bar displays "main". If it does not, initialize your project with Git. Open the Terminal tab and enter this command:
git init -b main
If the menu bar displays "master", run this command:
git checkout -b main
Note that files in the project panel may be red. This red text does not mean the file has an error. It means that the file is uncommitted with Git.
Open .gitignore and add this line.
.env
Create a .env file in the src/main/resources folder. Add this line to the file:
# Key=Value

Git Setup

Click the Git menu and select Commit.
Select the files that you want to commit, including Unversioned Files. Note that the .env file should not be listed.
Uncheck the "Analyze Code" and "Check TODO" boxes.
Write a commit message. The message should be a short description of what you recently accomplished.
Initial commit
Click "Commit". Don't click "Commit and Push".
If a "Line Separators Warning" message displays, check the "Don't warn again" box and click "Fix and Commit".
Note that the files are no longer red in the project panel.

GitHub Setup

Create a new private repository on GitHub. Title the repository "java-demos". Copy the URL.
Enter this command in the terminal:
git remote add origin https://github.com/YOUR-USERNAME/java-demos.git
Click the Git menu and select "Push".
Verify that your main branch is being pushed to the origin's (GitHub's) main branch. Verify the files that are being pushed.
The first time you do this you will need to sign into GitHub
- Windows Users: Sign in with your GitHub password.
- Mac Users: When signing in with your GitHub password, you may get an error saying you need to use a personal access token. See the next slide for instructions.

Mac Users

Click "Log In with Token".
Click "Generate".
Log in to your GitHub account.
You will be on a screen to generate a new personal access token. The note should be pre-filled with "IntelliJ IDEA GitHub integration plugin".
Set the expiration date to be after the semester ends (or Never).
Select the Repo check box.
Click Generate Token and copy the token that is generated.
Paste the token as the password in the IntelliJ GitHub popup.
In the Terminal app, enter this command so you only have to enter the token once.
git config --global credential.helper cache

GitHub Setup

Refresh your GitHub repository page to see the changes.
As we advance, commit regularly. Please change commit messages each time to something short and descriptive. Only push to GitHub when your work is ready to grade.
Student To-do:
- Click the "Settings" tab
- Choose Access > Collaborators, and click "Add people".
- Type "mlhaus" and select the instructor's profile. The instructor will grade all assignments via GitHub.
Instructor To-do:
- Click the "Settings" tab, then set the visibility to public so students can access it.
- Copy and paste a link to the course content so students always have access to demo code.

Java 2

Topics

What is UML?

UML Textbook

Class Diagrams

Three Boxes

Access Modifiers

Data Types, Parameters, Return

Inheritance

Associations

Composition Associations

Association Multiplicity

UML Diagramming Tools

Week 1 Lab

Week 1 Assignment

New Java Project

LearnxUser Class

Student Class

StudentDAO Class

SeatingChartBuilder Class

Git Setup

Git Setup

Git Setup

Mac Users

Git Setup

Git Setup

Git Setup

GitHub Setup

Mac Users

GitHub Setup

Java 2 - Week 1

Java 2 - Week 1

Marc Hauschildt

Java 2

Topics

What is UML?

UML Textbook

Class Diagrams

Three Boxes

Access Modifiers

Data Types, Parameters, Return

Inheritance

Associations

Composition Associations

Association Multiplicity

UML Diagramming Tools

Week 1 Lab

Week 1 Assignment

New Java Project

LearnxUser Class

Student Class

StudentDAO Class

SeatingChartBuilder Class

Git Setup

Git Setup

Git Setup

**Mac Users**

Git Setup

Git Setup

Git Setup

GitHub Setup

**Mac Users**

GitHub Setup

Java 2 - Week 1

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Mac Users

Mac Users