CMPUT 301 - Lab 1

Lab 1

Download and install Android Studio from the official Android website

Check for specific installation guide unique to your Operating System

Create a new LonelyTwitter project (File > New > New Project > Select "Empty Views Activity"). Make sure that the project language is Java, not Kotlin!
Create Tweet Class (Click > New > Java Class)
Make attributes (Date date & String message) (use alt+enter (windows) or Option-Enter (Mac) to include/import any packages)
- Note: Access modifiers
  - private= class only
  - No modifier = within package
  - protected = within package and through inheritance
  - public = everyone!
Create two Constructors (one with the only Message and the other with Date+Message as arguments) and use Date = new Date() (current date and time) for the first constructor (the Default value for date).
Note: Java Object Class (everything extends it, calls its constructor and it has built-in methods like toString())
Note: the this keyword (message = message doesn't do anything!)
Make a regular tweet in MainActivity (pass in an empty string)
Getters and setters
Inheritance
Make ImportantTweet child class (extends Tweet)
- call super in both of ImportantTweet's constructors
Now have access to the parent's methods and attributes. except constructors! (try and make an important Tweet)

ImportantTweet(String message){
        super(message);
    }

Super calls the parent's constructor (there is a hidden call to Object's constructor)
Change the Tweet to an ImportantTweet in MainActivity
Abstract Stuff
Make Tweet Class Abstract
- public abstract class Tweet { ... }
  - Note: Abstract classes cannot be instantiated.
- public abstract Boolean isImportant();
  - This is an abstract method, it has no implementation and must be overridden by child classes (to add functionality).
  - Note: Abstract methods cannot be called using any objects.
What if they need to behave differently? @Override isImportant() to create a compile-time check
- You need to override the method in the child class as it is an abstract method in the parent class that has no implementation.
- Overriding the method allows the child class to have its own implementation of the method.
  - ex. the Normal Tweet is not important, so it returns false. The ImportantTweet is important, so it returns true.
- The methods in the child classes need to be overridden to behave differently.
Make a NormalTweet class, could have many types of tweets
- call super in both of NormalTweet's constructors
- isImportant method should return Boolean.FALSE
- What if we want to use both in our list? (Implicit upcasting)

ArrayList tweetList = new ArrayList(); tweetList.add(normalTweet);

public interface Tweetable {
     public String getMessage();
     public Date getDate();
   }

Add three new model classes to LonelyTwitter: the first should be an abstract base class which represents the current mood. The second and third should be non-abstract classes which represent different moods (Ex: happy, sad, etc.) and inherit from the abstract class.
Each mood should have a date and getters and setters to access the date.
A constructor which sets the date to a default and a constructor which takes a date as an argument should be provided.
Encapsulation should be followed.
Each mood should have a method which returns a string representing that mood.
Your new code should have examples of classes, methods, attributes, access modifiers, encapsulation, constructors, inheritance and abstract base classes.

Note: Running the project is not necessary.

Zip the project and upload it to eClass.