Lesson 9 - More OOP

DIY - Creating Fib Class (10 minutes)

Fibonacci Sequence using LMC | 101 Computing

create a Fib class that can run the following code:

Fib fib = new Fib();
fib.next(2);
System.out.println(fib);
System.out.println(fib.next(3));
System.out.println(fib.next().next());


Fib fib2 = new Fib(7).next().prev();
System.out.println(fib2);

System.out.println("are fibs equal? " + (fib.equals(fib2) ? "yes" : "no"));

Fib(2) = 3
Fib(5) = 13
Fib(7) = 34
Fib(7) = 34
are fibs equal? yes

Solution

Main.java

public class Main {
    public static void main(String[] args) {
        Fib fib = new Fib();
        fib.next(2);
        System.out.println(fib);
        System.out.println(fib.next(3));
        System.out.println(fib.next().next());

        Fib fib2 = new Fib(6).next();
        System.out.println(fib2);

        System.out.println("are fibs equal? " + (fib.equals(fib2) ? "yes" : "no"));
    }
}

Fib.java

public class Fib {
    private int a;
    private int b;
    private int n;

    Fib() {
        this(0); // call: Fib(int num),  don't increment
    }

    Fib(int num) {
        a = 0;
        b = 1;
        n = 0;

        next(num);
    }

    Fib next() {
        return next(1);
    }

    Fib next(int num) {
        while (num > 0){
            int temp = a;
            a = b;
            b += temp;
            --num;
            ++n;
        }
        return this;
    }

    Fib prev() {
        return prev(1);
    }

    Fib prev(int num) {
        while (num > 0 && n > 1){
            int temp = a;
            a = b - a;
            b = temp;
            --num;
            --n;
        }
        return this;
    }

    @Override
    public String toString() {
        return "Fib(" + n + ") = " + (a+b) ;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Fib fib = (Fib) o;
        return n == fib.n;
    }
}

Fib(2) = 3
Fib(5) = 13
Fib(7) = 34
Fib(7) = 34
are fibs equal? yes

Creating an IntList

Main.java

public class Main {
    public static void main(String[] args) {
        IntList list = new IntList(4, 10);
        list.add(20).add(30);

        System.out.println(list);

        for (int i = 0; i < list.length() ; i++)
            System.out.print(list.get(i) + " ,");

        System.out.println("\n======= Equals =======\n");
        IntList new_list = new IntList(list); // Calls copy constructor

        System.out.println("new_list: " + new_list.toString());
        System.out.println("are the list the same: " + new_list.equals(list));

        new_list.add(100);
        System.out.println("new_list: " + new_list);
        System.out.println("are the list the same: " + new_list.equals(list));

        new_list.remove_index(6);
        System.out.println("new_list: " + new_list);
        System.out.println("are the list the same: " + new_list.equals(list));
    }
}

IntList .java

import java.util.Arrays;

public class IntList {
    private int size = 0; // shouldn't be public
    private static final int DEFAULT_CAPACITY = 10;
    private int[] elements;

    // ===== Constructors =====

    //default constructor
    public IntList() {
        elements = new int[DEFAULT_CAPACITY]; // or: this(DEFAULT_CAPACITY)
    }

    // Create int list with x elements, no values
    public IntList(int size) {
        elements = new int[size];
    }

    // Create int list with x elements, no values
    public IntList(int size, int num_2_fil) {
        elements = new int[size];
        this.size = size;
        Arrays.fill(elements, num_2_fil);
    }

    // copy constructor
    public IntList(IntList other) {
        size = other.size;
        elements = new int[size];

        //deep copy, could also use:
        //elements = Arrays.copyOf(other.elements, other.size);
        for (int i = 0; i < other.length(); i++)
            elements[i] = other.elements[i]; // or other.add(elements[i])
    }


    // ===== methods =====

    //add elemements
    public IntList add(int elem) {
        if (size == elements.length) {
            increaseCapacity();
        }
        elements[size++] = elem;

        return this; //<--------- show without returning this
    }

    //add elemements
    public IntList add(int elem, int amount) {
        while (amount>=0){
            if (size == elements.length)
                increaseCapacity();

            elements[size++] = elem;
            --amount;
        }

        return this; //<--------- show without returning this
    }

    //double the capacity
    private void increaseCapacity() {
        int newSize = elements.length * 2;
        elements = Arrays.copyOf(elements, newSize);
    }

    //get index
    public int get(int i) {
        if (i>= size || i <0)
            return -1;

        return elements[i];
    }

    public int length() {
        return size;
    }


    //remove index
    public int remove_index(int index) {
        int removed_elem;

        if (index>= size || index <=0)
            return -1;

        removed_elem = elements[index];
        size--;

        //end of IntList
        if (index==elements.length-1){
            elements[index] = 0;
        }

        for (int i = index; i < elements.length; i++)
            if (i+1<elements.length)
                elements[i] = elements[i+1];

        return removed_elem;
    }


    // ===== toString & equals =====

    @Override
    public String toString() {
        StringBuilder elems = new StringBuilder("[");
        for (int i = 0; i < size-1; i++)
            elems.append(elements[i] + ", ");
        elems.append(elements[size-1] + "]");


        return "IntList{" +
                "size=" + size +
                ", capacity=" + elements.length +
                ", elements=" + elems.toString() +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        IntList intList = (IntList) o;

        if (size == intList.size){
            for (int i = 0; i < size; i++)
                if (elements[i] != intList.get(i))
                    return false;

            return true;
        }
        return false;

//        return size == intList.size
//                && Arrays.equals(elements, intList.elements);
    }
}

IntList{size=6, capacity=8, elements=[10, 10, 10, 10, 20, 30]}
10 ,10 ,10 ,10 ,20 ,30 ,

======= Equals =======
new_list: IntList{size=6, capacity=6, elements=[10, 10, 10, 10, 20, 30]}
are the list the same: true
new_list: IntList{size=7, capacity=12, elements=[10, 10, 10, 10, 20, 30, 100]}
are the list the same: false
new_list: IntList{size=6, capacity=12, elements=[10, 10, 10, 10, 20, 30]}
are the list the same: true

another example

public class Main {
    public static void main(String[] args) {
        IntList list = new IntList(4, 10).add(20);
        System.out.println(list);

        list.add(100,4).remove_index(4);
        System.out.println(list);
    }
}

IntList{size=5, capacity=8, elements=[10, 10, 10, 10, 20]}
IntList{size=9, capacity=16, elements=[10, 10, 10, 10, 100, 100, 100, 100, 100]}

Polygon (Point list)

Source: https://www.geogebra.org/m/amtvtmvv

polygon-list

Lets change a few properties of our IntList and create a PointList

we will add a few fields

• Color color

• String name

and a method to convert the the x and y to a list of double

• double[] convert2DoubleArray(String x_or_y)

Main

public class Main {
    public static void main(String[] args) {
        Polygon list = new Polygon(3, new Point(1, 2)).add(new Point(30, 40));
        System.out.println(list);

        list.add(new Point(-100, -100),3).remove_index(4);
        System.out.println(list);

        Polygon new_list = new Polygon(list);
        System.out.println("are the Polygons the same? " + list.equals(new_list));
        list.remove_index(3);
        System.out.println("are the Polygons the same? " + list.equals(new_list));

    }
}

Polygon

import java.util.Arrays;

import java.awt.*;
import java.util.Arrays;

public class Polygon {
    private int size = 0; // shouldn't be public
    private static final int DEFAULT_CAPACITY = 10;
    private Point[] elements;
    private Color color;
    private String name = new String("");

    // ===== Constructors =====

    //default constructor
    public Polygon() {
        this(DEFAULT_CAPACITY); //call Polygon(int size);
    }

    // Create Polygon with x elements, no values
    public Polygon(int size) {
        elements = new Point[size];
        setColor(0,0,255);
    }

    // Create int Polygon with x elements, no values
    public Polygon(int size, Point point_2_fil) {
        elements = new Point[size];
        this.size = size;
        Arrays.fill(elements, point_2_fil);
        setColor(0,0,255);
    }

    // copy constructor
    public Polygon(Polygon other) {
        size = other.size;
        elements = new Point[size];
        color = other.color;

        for (int i = 0; i < other.length(); i++)
            elements[i] = other.elements[i]; // or other.add(elements[i])
    }


    // ===== methods =====

    private double[] convert2DoubleArray(String x_or_y) {
        double[] list = new double[elements.length];

        switch (x_or_y) {
            case "x":
                for (int i = 0; i < size; i++)
                    list[i] = elements[i].getX();
                return list;
            //break;
            case "y":
                for (int i = 0; i < size; i++)
                    list[i] = elements[i].getY();
                return list;
            default:
                return new double[]{0., 0.};
        }
    }

    public void setColor(int r, int g, int b) {
        this.color = new Color(r, g, b);
    }

    public void draw() {
        StdDraw.setPenColor(color);
        StdDraw.filledPolygon(convert2DoubleArray("x"), convert2DoubleArray("y"));
    }

    //add elemements
    public Polygon add(Point elem) {
        if (size == elements.length) {
            increaseCapacity();
        }
        elements[size++] = elem;

        return this; //<--------- show without returning this
    }

    //add elemements
    public Polygon add(Point elem, int amount) {
        while (amount>=0){
            if (size == elements.length)
                increaseCapacity();

            elements[size++] = elem;
            --amount;
        }

        return this; //<--------- show without returning this
    }

    //double the capacity
    private void increaseCapacity() {
        int newSize = elements.length * 2;
        elements = Arrays.copyOf(elements, newSize);
    }

    //get index
    public Point get(int i) {
        if (i>= size || i <0)
            return new Point();

        return elements[i];
    }

    public int length() {
        return size;
    }


    //remove index
    public Point remove_index(int index) {
        Point removed_elem;

        if (index>= size || index <=0)
            return new Point();

        removed_elem = elements[index];
        size--;

        //end of Polygon
        if (index==elements.length-1){
            elements[index] = new Point();
        }

        for (int i = index; i < elements.length; i++)
            if (i+1<elements.length)
                elements[i] = elements[i+1];

        return removed_elem;
    }


    // ===== toString & equals =====

    @Override
    public String toString() {
        StringBuilder elems = new StringBuilder("[");
        for (int i = 0; i < size-1; i++)
            elems.append(elements[i] + ", ");
        elems.append(elements[size-1] + "]");


        return "Polygon{" +
                "size=" + size +
                ", capacity=" + elements.length +
                ", elements=" + elems.toString() +
                '}';
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Polygon polygon = (Polygon) o;

        if (size == polygon.size){
            for (int i = 0; i < size; i++)
                if (elements[i] != polygon.get(i))
                    return false;

            return true;
        }
        return false;

    }
}

Point.java

class Point {
    private double x, y;

    //=== constructors ===

    //default constructor
    Point() {
        x =0;
        y = 0;
    }

    Point(double new_x, double y) {
        x = new_x;
        this.y = y;
    }

    //copy constructor
    Point(Point p) {
        x = p.x; // Since this is the same class I can access without getter/setter
        y = p.y;
    }

    //=== static methods ===
    public static double distance(Point a, Point b) {
        double dist = Math.pow(a.x-b.x, 2) + Math.pow(a.y-b.y, 2);
        return Math.sqrt(dist);
    }



    //=== getters and setters ===
    public double getX() {
        return x;
    }

    public void setX(double x) {
        this.x = x;
    }

    public double getY() {
        return y;
    }

    public void setY(double y) {
        this.y = y;
    }

    public String toString() {
        return "Point {" + " x=" + x + ", y=" + y + " }";
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Point point = (Point) o;
        return Double.compare(point.x, x) == 0 && Double.compare(point.y, y) == 0;
    }
}

PointList{size=4, capacity=6, elements=[Point { x=1.0, y=2.0 }, Point { x=1.0, y=2.0 }, Point { x=1.0, y=2.0 }, Point { x=30.0, y=40.0 }]}

PointList{size=7, capacity=12, elements=[Point { x=1.0, y=2.0 }, Point { x=1.0, y=2.0 }, Point { x=1.0, y=2.0 }, Point { x=30.0, y=40.0 }, Point { x=-100.0, y=-100.0 }, Point { x=-100.0, y=-100.0 }, Point { x=-100.0, y=-100.0 }]}

are the Polygons the same? true
are the Polygons the same? false

Drawing the polygon

Lets now draw a Polygon (Point list with at least 3 points + the first point to close the loop)

The points in the polygon are (x[i], y[i]). For example, the following code fragment draws a filled diamond with vertices (0.1, 0.2), (0.2, 0.3), (0.3, 0.2), and (0.2, 0.1):

   double[] x = { 0.1, 0.2, 0.3, 0.2 };
   double[] y = { 0.2, 0.3, 0.2, 0.1 };
   StdDraw.filledPolygon(x, y);

so we need to add the following function to Polygon

private double[] convert2DoubleArray(String x_or_y) {
        double[] list = new double[elements.length];

        switch (x_or_y) {
            case "x":
                for (int i = 0; i < size; i++)
                    list[i] = elements[i].getX();
                return list;
            //break;
            case "y":
                for (int i = 0; i < size; i++)
                    list[i] = elements[i].getY();
                return list;
            default:
                return new double[]{0., 0.};
        }
    }

public class Main {
    public static void main(String[] args) {
        Polygon polygon1 = new Polygon();
        polygon1.add(new Point(20,20));
        polygon1.add(new Point(80,20));
        polygon1.add(new Point(50,70));
        polygon1.add(new Point(20,20));

        Polygon polygon2 = new Polygon();
        polygon2.setColor(0,255,0);
        polygon2.add(new Point(80,20));
        polygon2.add(new Point(90,40));
        polygon2.add(new Point(50,70));
        polygon2.add(new Point(80,20));


        StdDraw.setXscale(0, 100);
        StdDraw.setYscale(0, 100);
        polygon1.draw();
        polygon2.draw();
    }
}

or

public class Main {
    public static void main(String[] args) {
        Polygon[] polygons = new Polygon[3];

        polygons[0] = new Polygon();
        polygons[0].add(new Point(229,153));
        polygons[0].add(new Point(160,218));
        polygons[0].add(new Point(177,325));
        polygons[0].add(new Point(249,268));
        polygons[0].add(new Point(229,153));


        polygons[1] = new Polygon();
        polygons[1].setColor(0,255,0);
        polygons[1].add(new Point(249,268));
        polygons[1].add(new Point(177,325));
        polygons[1].add(new Point(269,336));
        polygons[1].add(new Point(349,283));
        polygons[1].add(new Point(249,268));

        polygons[2] = new Polygon().setName("redPolygon");
        polygons[2].setColor(255,0,0);
        polygons[2].add(new Point(349,283));
        polygons[2].add(new Point(328,182));
        polygons[2].add(new Point(229,153));
        polygons[2].add(new Point(249,268));
        polygons[2].add(new Point(349,283));


        StdDraw.setXscale(0, 500);
        StdDraw.setYscale(0, 500);

        for (int i = 0; i < polygons.length; i++) {
            polygons[i].draw();
            System.out.println(polygons[i]);
        }

    }
}

polygon_1: Polygon{num of points: 5, capacity=10, elements=[Point { x=229.0, y=153.0 }, Point { x=160.0, y=218.0 }, Point { x=177.0, y=325.0 }, Point { x=249.0, y=268.0 }, Point { x=229.0, y=153.0 }]}

polygon_2: Polygon{num of points: 5, capacity=10, elements=[Point { x=249.0, y=268.0 }, Point { x=177.0, y=325.0 }, Point { x=269.0, y=336.0 }, Point { x=349.0, y=283.0 }, Point { x=249.0, y=268.0 }]}

redPolygon: Polygon{num of points: 5, capacity=10, elements=[Point { x=349.0, y=283.0 }, Point { x=328.0, y=182.0 }, Point { x=229.0, y=153.0 }, Point { x=249.0, y=268.0 }, Point { x=349.0, y=283.0 }]}