Slide 1More on ObjectsTest-First ApproachMathematical PointJava Coordinate SystemPoint InterfaceStubs for ACartesianPointACartesianPoint TesterPoint RepresentationsAlgorithmsClass: ACartesianPointClass: APolarPointUsing the Interface and Its ImplementationsRepresenting Geometric ObjectsUsing ObjectEditorJava GraphicsAdding Tree ViewTree ViewRemoving Graphics ViewTree-only ViewObjectEditor GraphicsObjectEditor Point RulesEquivalent RepresentationsReason for ErrorWhat is in a Representation?Typing Point ObjectsLine?Describing LinesLine InterfaceLine ImplementationAnotherLine InterfaceSlide 32Predefined, Primitive vs. Programmer-Defined, ObjectKinds of TypesProgrammer-defined vs. Predefined TypesStructured vs. Atomic PropertiesStructure vs. Atomic TypesDecomposing AnAnotherLine InstancePhysical StructureLogical StructureLogical Structure Shown by ObjectEditorPhysical Structure Shown by DebuggerTwo Ways to Decompose ObjectsDrawing the Physical Structure of a Value of Some TypeDrawing the Logical Structure of a Value of Some TypeInstance-Specific StructureInstance-Specific StructureAtomic vs. Structure TypesGraphics Types Sees So FarObjectEditor Shape RulesXY-based ObjectEditor Shape RulesPoint-based ObjectEditor Shape RulesObjectEditor Bounding Box RulesObjectEditor Shape RulesObjectEditor TextBox RulesObjectEditor Label RulesLabel ImplementationUsing ALabelCreating Other Geometric ObjectsACartesianPlaneACartesianPlaneACartesianPlane PropertiesACartesianPlane PropertiesACartesianPlane StubsACartesianPlane ImplementationACartesianPlane ImplementationACartesianPlane ImplementationRefactoring Label CodeRefactoring Label CodeACartesianPlaneShuttle LocationShuttle LocationShuttle LocationShuttleLocation PropertiesAShuttleLocation ImplementationAShuttleLocation ImplementationAlternate Views of Logical StructureLines of CompositionEXTRA SLIDESAScalableNesterCOMP 401REPRESENTATIONInstructor: Prasun Dewan2MORE ON OBJECTSTest-first approachStubsTwo-way dependenciesRepresentations with errorsStructure vs. atomic typesPhysical vs. logical structureGraphics types3TEST-FIRST APPROACHWrite the interfaceCreate a class with stubs for each interface method and constructorIf method is procedure method does nothingIf method is function, it returns 0 or null valueNo variables need be declared as this point!Write a tester for itWrite/rewrite in one or more stub methodsUse testerIf tester results not correct, go back to 4Steps may be combined for simple classes!4MATHEMATICAL POINTX.Y Rq.5JAVA COORDINATE SYSTEMYX(0,0)(3,2)pixelsX and Y coordinates must be int valuesRadius and Angle can be doubleAngle is a decimal value between 0 and 26POINT INTERFACEpublic interface Point {public int getX(); public int getY(); public double getAngle(); public double getRadius(); }Read-only properties defining immutable object!7STUBS FOR ACARTESIANPOINTpublic class ACartesianPoint implements Point {public ACartesianPoint(int theX, int theY) { }public int getX() {return 0;}public int getY() {return 0;} public double getAngle() {return 0;}public double getRadius() {return 0;}}8ACARTESIANPOINT TESTERpublic class ACartesianPointTester {public void test (int theX, int theY, double theCorrectRadius, double theCorrectAngle) {Point point= new ACartesianPoint (theX, theY);double computedRadius = point.getRadius();double computedAngle = point.getAngle();System.out.println("------------");System.out.println(“X:" + theX);System.out.println(“Y:" + theY);System.out.println("Expected Radius:" + theCorrectRadius);System.out.println("Computed Radius:" + computedRadius);System.out.println(“Radius Error:" + (theCorrectRadius - computedRadius));System.out.println("Expected Angle:" + theCorrectAngle);System.out.println("Computed Angle:" + computedAngle);System.out.println(“Angle Error:" + (theCorrectAngle - computedAngle));System.out.println("------------");}public void test () {test (10, 0, 10.0, 0); // 0 degree angletest (0, 10, 10.0, Math.PI / 2); // 90 degree angle}}9POINT REPRESENTATIONSX, Y (Cartesian Representation)Radius, Angle (Polar Representation)X, RadiusX, Y, Radius, Angle…Does not completely specify the point10ALGORITHMSX.Y Rq.Cartesian RepresentationR = sqrt (X2 * Y2) = arctan (Y/X)Polar RepresentationX = R*cos()Y = R*sin()11CLASS: ACARTESIANPOINTpublic class ACartesianPoint implements Point {int x, y;public ACartesianPoint(int theX, int theY) {x = theX;y = theY;}public int getX() {return x;}public int getY() {return y;} public double getAngle() {return Math.atan2(y, x);}public double getRadius() {return Math.sqrt(x*x + y*y);}}12CLASS: APOLARPOINTpublic class APolarPoint implements Point {double radius, angle;public APolarPoint(double theRadius, double theAngle) {radius = theRadius ;angle = theAngle;}public int getX() {return (int) (radius*Math.cos(angle));}public int getY() {return (int) (radius*Math.sin(angle));}public double getAngle() {return angle;} public double getRadius() {return radius;}}13USING THE INTERFACE AND ITS IMPLEMENTATIONSPoint point1 = new ACartesianPoint (50, 50); Point point2 = new APolarPoint (70.5, Math.pi()/4); point1 = point2;Constructor chooses implementationConstructor cannot be in interface14REPRESENTING GEOMETRIC OBJECTSGeometric example to show multiple useful implementations of an interfaceMost geometric objects have multiple representations15USING OBJECTEDITORObjectEditor.edit(new ACartesianPoint (25, 50));16JAVA GRAPHICSYX17ADDING TREE VIEW18TREE VIEW19REMOVING GRAPHICS VIEW20TREE-ONLY VIEW21OBJECTEDITOR GRAPHICSCan automatically display objects representing points, rectangles, ovals, and lines as corresponding graphicsJava provides libraries to manually display graphicsHas rules for recognizing these objectsRules based on Java graphics standardsInverted coordinate systemCartesian coordinates for pointsBounding rectangles for lines, rectangles, ovalsPlus naming conventions22OBJECTEDITOR POINT RULESAn object is recognized as a point representation if:Its interface or class has the string “Point” in its nameIt has readable int properties, x and y, representing Cartesian coordinatesCan have additional propertiespublic interface Point {public int getX(); public int getY(); public double getAngle(); public double getRadius(); }23ObjectEditor.edit(new APolarPoint (195.05, 0.87)); ObjectEditor.edit(new ACartesianPoint (125, 149)); EQUIVALENT