Background: Suppose we are creating a software to manage various tasks a person has to do. Two types of such tasks are,

• Todos: i.e., things that needs to be done some day e.g., 'Read the book Lord of the Rings'
• Deadlines: i.e., things to be done by a specific date/time e.g., 'Read the text book by Nov 25th'

The Task class is given below:

public class Task {
    protected String description;

    public Task(String description) {
        this.description = description;
    }

    public String getDescription() {
        return description;
    }
}

1. Write a Todo class that inherits from the Task class.
   • It should have an additional boolean field isDone to indicate whether the todo is done or not done.
   • It should have a isDone() method to access the isDone field and a setDone(boolean) method to set the isDone field.
2. Write a Deadline class that inherits from the Todo class that you implemented in the previous step. It should have,
   • an additional String field by to store the details of when the task to be done e.g., Jan 25th 5pm
   • a getBy() method to access the value of the by field, and a corresponding setBy(String) method.
   • a constructor of the form Deadline(String description, String by)

The expected behavior of the two classes is as follows:

public class Main {
    public static void main(String[] args) {
        // create a todo task and print details
        Todo t = new Todo("Read a good book");
        System.out.println(t.getDescription());
        System.out.println(t.isDone());

        // change todo fields and print again
        t.setDone(true);
        System.out.println(t.isDone());

        // create a deadline task and print details
        Deadline d = new Deadline("Read textbook", "Nov 16");
        System.out.println(d.getDescription());
        System.out.println(d.isDone());
        System.out.println(d.getBy());

        // change deadline details and print again
        d.setDone(true);
        d.setBy("Postponed to Nov 18th");
        System.out.println(d.isDone());
        System.out.println(d.getBy());
    }
}

Read a good book
false
true
Read textbook
false
Nov 16
true
Postponed to Nov 18th

Suppose you have the following classes Task, Todo, Deadline:

public class Task {
    protected String description;

    public Task(String description) {
        this.description = description;
    }

    public String getDescription() {
        return description;
    }
}

public class Todo extends Task {
    protected boolean isDone;

    public Todo(String description) {
        super(description);
        isDone = false;
    }

    public void setDone(boolean done) {
        isDone = done;
    }

    public boolean isDone() {
        return isDone;
    }
}

public class Deadline extends Todo {

    protected String by;

    public Deadline(String description, String by) {
        super(description);
        this.by = by;
    }

    public void setBy(String by) {
        this.by = by;
    }

    public String getBy() {
        return by;
    }
}

Override the toString method of the three classes to produce the following behavior.

public class Main {
    public static void main(String[] args) {
        // create a todo task and print it
        Todo t = new Todo("Read a good book");
        System.out.println(t);

        // change todo fields and print again
        t.setDone(true);
        System.out.println(t);

        // create a deadline task and print it
        Deadline d = new Deadline("Read textbook", "Nov 16");
        System.out.println(d);

        // change deadline details and print again
        d.setDone(true);
        d.setBy("Postponed to Nov 18th");
        System.out.println(d);
    }
}

description: Read a good book
is done? No
description: Read a good book
is done? Yes
description: Read textbook
is done? No
do by: Nov 16
description: Read textbook
is done? Yes
do by: Postponed to Nov 18th

You can use the super.toString from the subclass to invoke the behavior of the method you are overriding. This is useful here because the overriding method is simply adding onto the behavior of the overridden method.

The Main class below passes a list of Printable objects (i.e., objects that implement the Printable interface) for another method to be printed.

public class Main {

    public static void printObjects(Printable[] items) {
        for (Printable p : items) {
            p.print();
        }
    }

    public static void main(String[] args) {
        Printable[] printableItems = new Printable[]{
                new Circle(5),
                new Rectangle(3, 4),
                new Person("James Cook")};

        printObjects(printableItems);
    }
}

Circle of area 78
Rectangle of area 12
Person of name James Cook

Classes Shape, Circle, and Rectangle are given below:

public abstract class Shape {

    public abstract int area();
}

public class Circle extends Shape implements Printable {

    private int radius;

    public Circle(int radius) {
        this.radius = radius;
    }

    @Override
    public int area() {
        return (int)(Math.PI * radius * radius);
    }

    @Override
    public void print() {
        System.out.println("Circle of area " + area());
    }
}

public class Rectangle extends Shape implements Printable {
    private int height;
    private int width;

    public Rectangle(int height, int width){
        this.height = height;
        this.width = width;
    }

    @Override
    public int area() {
        return height * width;
    }

    @Override
    public void print() {
        System.out.println("Rectangle of area " + area());
    }
}

Add the missing Printable interface. Add the missing methods of the Person class given below.

public class Person implements Printable {

    private String name;

    // todo: add missing methods
}