Demo - Aggregation Example

https://www.youtube.com/watch_popup?v=gyeUK9GAE3c

package ClassDemo;

/*  
 * 	Class handles an Address 
 */
public class Address {
	
	
	private String streetAddress;
	private String city;
	private String state;
	private String zip;
	
	//Getters and Setters
	public String getStreetAddress() {
	return streetAddress;
	}
	public void setStreetAddress(String streetAddress) {
		this.streetAddress = streetAddress;
	}
	public String getCity() {
		return city;
	}
	public void setCity(String city) {
		this.city = city;
	}
	public String getState() {
		return state;
	}
	public void setState(String state) {
		this.state = state;
	}
	public String getZip() {
		return zip;
	}
	public void setZip(String zip) {
		this.zip = zip;
	}
	
	
	/** Constructor 
	 * @param streetAddress
	 * @param city
	 * @param state
	 * @param zip
	 */
	public Address(String streetAddress, String city, String state, String zip) {
		super();
		this.streetAddress = streetAddress;
		this.city = city;
		this.state = state;
		this.zip = zip;
	}
	/**Default Constructor 
	 */
	public Address() {
		this.streetAddress = "Unknown Street Address";
		this.city = "Unknown City";
		this.state  = "Unknown State";
		this.zip  = "Unknown Zip";
	
	}	
	/**Copy Address Constructor to handle the reference (value passed by reference)
	 */
	public Address(Address pAdd)
	{
		this.streetAddress = pAdd.streetAddress;
		this.city = pAdd.city;
		this.state = pAdd.state;
		this.zip = pAdd.zip;
		
	}
	/*
	 * Functions/Methods 
	 */	
	public String PrintAddress()
	{		
		String myReturn = "";		
		myReturn += "\t" + getStreetAddress() + "\n";
		myReturn += "\t" + getCity() + ", " + getState() + ", " + getZip(); 		
		return myReturn;
	}
	
}

The provided Java code is a class definition for an Address class in the package ClassDemo. This class is used to model a real-world address, which typically includes attributes like street address, city, state, and zip code.

Here's a breakdown of the class and its components:

Fields: There are four private fields (streetAddress, city, state, zip) representing the parts of an address.
Getters and Setters: There are getter and setter methods for each field. These methods are used to retrieve (get) and change (set) the value of the fields.
Constructor with parameters: This is a constructor that takes four parameters. It initializes a new Address object with the provided street address, city, state, and zip code. The super() call is unnecessary in this case because Address does not explicitly extend any other class other than Object, which is implicitly extended by all classes in Java.
Default Constructor: This is a no-argument constructor that initializes a new Address object with the default values (all set to "Unknown").
Copy Constructor: This constructor takes an Address object as a parameter. It initializes a new Address object with the same values as the provided object. This is used to create a copy of an Address object.
PrintAddress Method: This method returns a formatted string representation of the Address object. It concatenates the values of the streetAddress, city, state, and zip fields and returns this string. This can be useful for displaying the address information in a readable format.

In summary, this Address class provides a way to model addresses within a Java application, including functionality to create new addresses, modify them, and print them in a standard format.

Person Class

package ClassDemo;

/**
 * Class contains First name, Last name, and age 
 * Class uses aggregation to also contain Work/Home address 
 */
public class Person {

	//Attributes/fields
	private String firstName;
	private String lastName;
	private int personAge;
	private Address HomeAddress; //this is the Address Class
	private Address WorkAddress; //Address Class


	/**************************************
	 * Constructors
	 **************************************/	
	//Constructors (Default)
	public Person()
	{
		firstName = "None";
		lastName = "None";
		personAge = 0;	
		HomeAddress = new Address();
		WorkAddress = new Address();

	}

	//Constructors (Populates data with arguments)
	public Person(String pFirst, String pLast, int pAge, Address pWork, Address pHome)
	{
		setFirstName(pFirst);		
		setLastName(pLast);
		setPersonAge(pAge);	
		//to ensure we have the values and not just a refernce to the Address objects passed
		this.HomeAddress = new Address(pHome);
		this.WorkAddress = new Address(pWork);		
	}

	/**************************************
	 * Getters/Setters
	 **************************************/	

	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;
	}

	public int getPersonAge() {
		return personAge;
	}

	public void setPersonAge(int personAge) {
		this.personAge = personAge;
	}
	public Address getWorkAddress() {
		return WorkAddress;
	}

	public void setWorkAddress(Address pWork) {
		this.WorkAddress = new Address(pWork);
	}
	public Address getHomeAddress() {
		return HomeAddress;
	}

	public void setHomeAddress(Address pHome) {
		this.HomeAddress = new Address(pHome);
	}


	/**************************************
	 * Methods 
	 **************************************/
	public String PrintData()
	{
		String myReturn = "";
		myReturn += "Name: " + getFirstName() + " " + getLastName();
		myReturn += " Age: " + getPersonAge();

		//Home address 
		myReturn += "\nHome Address:\n";		
		myReturn += HomeAddress.PrintAddress();

		//Work address ";		
		myReturn += "\nWork Address:\n";
		myReturn += WorkAddress.PrintAddress();

		return myReturn;						
	}

	@Override
	public String toString() {
		return "Person [firstName=" + firstName + ", lastName=" + lastName + ", personAge=" + personAge + "]";
	}	
} // END Person Class

The provided Java code defines a Person class within the ClassDemo package. This class is designed to model a real-world person, capturing attributes such as first name, last name, age, home address, and work address.

Here's a detailed breakdown of the class and its components:

Fields: The class has five private fields: firstName, lastName, personAge, HomeAddress, and WorkAddress. firstName and lastName are Strings representing the person's name. personAge is an integer for the person's age. HomeAddress and WorkAddress are objects of the Address class representing the person's home and work addresses.
Default Constructor: The default constructor initializes a new Person object with default values. It sets the firstName and lastName to "None", the personAge to 0, and initializes HomeAddress and WorkAddress with the default Address constructor.
Constructor with parameters: This constructor initializes a new Person object using the provided parameters. It uses the setters for the fields firstName, lastName, and personAge, and the copy constructor of Address class to create new Address objects for HomeAddress and WorkAddress. This ensures that the address objects stored within the Person object are distinct from the ones passed in, which helps to maintain data integrity and avoid issues with shared references.
Getters and Setters: There are getter and setter methods for each field. These methods are used to retrieve (get) and change (set) the values of the fields.
PrintData Method: This method returns a string representation of the Person object. It concatenates the values of the firstName, lastName, personAge fields, and the string representations of the HomeAddress and WorkAddress objects. The addresses are fetched using the PrintAddress() method from the Address class.
toString Method: This method is overridden from the Object class. It returns a string representation of the Person object, including the firstName, lastName, and personAge fields. The addresses are not included in this representation.

Overall, the Person class models a person with their name, age, and address details (both home and work). The class is designed to ensure that each Person object maintains its own distinct Address objects, helping to prevent errors that could arise from mutable shared state.

package ClassDemo;

public class PersonDemo {
	public static void main(String[] args) {	
		
		
		Person myPerson = new Person();		
		//create 2 addresses
		Address myWorkAddress = new Address("1223 Fredricksburg Ave", "San Antonio", "Texas", "78451");
		Address myHomeAddress = new Address("45 2nd Street", "San Antonio", "Texas", "74123");
	
		//create a person and populate the addresses 
		myPerson = new Person("Kevin", "Roark", 39, myWorkAddress, myHomeAddress);
		
		//print data 
		System.out.println(myPerson.PrintData() );			
	}
}

This provided Java code is part of the ClassDemo package and defines a PersonDemo class with a main method. The purpose of this class is to demonstrate the use of the Person and Address classes.

Here's a breakdown of what's happening in the main method:

A Person object myPerson is created using the default constructor, which sets the fields to their default values as defined in the Person class.
Two Address objects, myWorkAddress and myHomeAddress, are created. The constructors are called with string arguments that set the street address, city, state, and zip code for each address.
Then, the myPerson object is assigned a new Person object. The constructor is called with string arguments for the first and last names, an integer for the age, and the previously created myWorkAddress and myHomeAddress objects. Because the Person constructor creates new Address objects from the ones provided, myPerson will have its own distinct address objects that match the ones created here.
Finally, the PrintData method of myPerson is called. This method returns a string that contains the first name, last name, age, and home and work address of the Person object. This string is then printed to the console.

In summary, this class demonstrates creating a Person object with specific data, and then printing that data to the console. The Person object is composed of a name, age, and two Address objects, all of which are defined in the code.