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public class Point //declares a class{

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public void move(double dx, double dy)// method to move a point

{ x+=dx; y+=dy; }}


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class Engine{

private double horsepower;Engine(double hp) { hp=horsepower; }void StartEngine();

}class Vehicle extends Engine // bad design{

Vehicle(double hp) { super(hp); }}Vehicle volvo = new Vehicle(80);volvo.StartEngine();


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class Engine{

private double horsepower;Engine(double hp) { hp=horsepower; }void StartEngine();

}class Vehicle {

private Engine engine;Vehicle (double hp) { engine=new Engine(hp); }void Start() { engine.StartEngine(); }

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abstract class Shape {abstract void move(double dx, double dy);abstract void rotate(double angle); // rotate around origin

abstract Point center(); // center Point of Shapevoid rotateshape(double angle) {…} // rotate Shape around

// centervoid rotate(Point p, double angle) { … } // rotate around Point p

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class Point extends Shape // subclass inherits from Shape{private double x,y;Point(double nx, double ny) { x=nx; y= ny;} // constructorvoid move(double dx, double dy) {x+=dx; y+=dy;}void rotate(double angle) {double tmp_x = x * Math.cos(angle) - y.Math.sin(angle); y = x * Math.cos(angle) + y.Math.sin(angle);

x=tmp_x;}Point center() {return this;} double GetX() { return x;}; double GetY() { return y;}

}



class Line extends Shape // subclass inherits from Shape{private Point p1, p2;Line(Point np1, Point np2) { p1=np1; p2=np2;} void move(double dx, double dy) {

p1.move(dx,dy); p2.move(dx,dy) }void rotate(double angle) {

p1.rotate(angle); p2.rotate(angle) }Point center() { new Point((p1.get_x()+p2.get_x())/2.0,((p1.get_y()+p2.get_y())/2.0)}

}



class Circle extends Shape // subclass inherits from Shape{private Point p;private double radius;Circle(Point np, double r) { p=np; radius=r;} void move(double dx, double dy) { p.move(dx,dy); }void rotate(double angle) { p.rotate(angle); }Point center() { return p; }

}



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Point p = new Point(10,10);Line l = new Line(new Point(0,0), new Point(10,20));Circle c = new Circle( new Point(5,5), 8);Shape s;s=c;s.move(5,10); // Shape bounds to Circle move()s=l;s.move(3,9); // Shape bounds to Line move()


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Point p=new Point(10,15);s=p;s.move(15,0);

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Shape s;Circle c=new Circle (new Point(0,0),5);s=c;s.move(10,15);

Line l=new Line(new Point(0,0),new Point(10,5));

s=l;s.move(10,10);

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Shape[] shapes = new Shape[3]; // Null references shapes[0] = new Point(3,9);shapes[1]= new Line( new Point(0,0),

new Point(10,20));shapes[2]=new Circle(new Point(15,5), 8);

for (int i=0; i<shapes.length; i++){

shapes[i].move(-10,0);shapes[i].rotate(new Point(4,5), Math.Pi/2);

}



abstract class Shape {public abstract void move(double dx, double dy);public abstract void rotate(double angle); // rotate around P(0,0)public abstract Point center(); // center Point of Shapepublic void rotateshape(double angle) // rotate around center{ rotate(center(),angle); }public void rotate(Point p, double angle) {

move(-p.get_x(),p.get_y());rotate(angle);move(p.get_x(),p.get_y());

}}



class Point extends Shape // subclass inherits from Shape{

private double x,y;Point(double nx, double ny) { x=nx; y= ny;} // constructorvoid move(double dx, double dy) {x+=dx; y+=dy;}void rotate(double angle) { … }void rotateshape(double angle) {} // overloads rotateshape() method in class ShapePoint center() {return this;} double GetX() { return x;}; double GetY() { return y;}

}


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Lecture 3 OOMPA Procedural Languages Object Oriented