Classes

1. Classes

2. Preparation • Scene so far has been background material and experience • Computing systems and problem solving • Variables • Types • Input and output • Expressions • Assignments • Objects • Standard classes and methods

3. Ready • Experience what Java is really about • Design and implement objects representing information and physical world objects

4. Object-oriented programming • Basis • Create and manipulate objects with attributes and behaviors that the programmer can specify • Mechanism • Classes • Benefits • An information type is design and implemented once and reused as needed • No need reanalysis and re-justification of the representation

5. Design an air conditioner representation • Context • Behaviors • Attributes

6. Design an air conditioner representation • Context • Repair person • Sales person • Consumer • Behaviors • Attributes

7. Design an air conditioner representation • Context – Consumer • Behaviors • Attributes

8. Design an air conditioner representation • Context - Consumer • Behaviors • Turn on • Turn off • Get temperature and fan setting • Set temperature and fan setting • Build – construction • Debug • Attributes

9. Design an air conditioner representation • Context - Consumer • Behaviors • Turn on • Turn off • Get temperature and fan setting • Set temperature and fan setting • Build – construction • Debug – to stringing • Attributes

10. Design an air conditioner representation • Context - Consumer • Behaviors • Turn on • Turn off • Get temperature and fan setting • Set temperature and fan setting – mutation • Build – construction • Debug – to stringing • Attributes

11. Design an air conditioner representation • Context - Consumer • Behaviors • Turn on • Turn off • Get temperature and fan setting – accessing • Set temperature and fan setting – mutation • Build – construction • Debug – to stringing • Attributes

12. Design an air conditioner representation • Context - Consumer • Behaviors • Turn on – mutation • Turn off – mutation • Get temperature and fan setting – accessing • Set temperature and fan setting – mutation • Build – construction • Debug – to stringing • Attributes

13. Design an air conditioner representation • Context - Consumer • Behaviors • Turn on – mutation • Turn off – mutation • Get temperature and fan setting – accessing • Set temperature and fan setting – mutation • Build – construction • Debug – to stringing • Attributes

14. Design an air conditioner representation • Context - Consumer • Behaviors • Turn on • Turn off • Get temperature and fan setting • Set temperature and fan setting • Build -- construction • Debug • Attributes • Power setting • Fan setting • Temperature setting

15. Design an air conditioner representation • Context - Consumer • Behaviors • Turn on • Turn off • Get temperature and fan setting • Set temperature and fan setting • Build -- construction • Debug • Attributes • Power setting • Fan setting • Temperature setting – integer

16. Design an air conditioner representation • Context - Consumer • Behaviors • Turn on • Turn off • Get temperature and fan setting • Set temperature and fan setting • Build -- construction • Debug • Attributes • Power setting – binary • Fan setting – binary • Temperature setting – integer

17. Design an air conditioner representation // Represent an air conditioner – from consumer view point public class AirConditioner { // instance variables // constructors // methods } • Source AirConditioner.java

18. Static variables and constants // shared resource for all AirConditioner objects static public final int OFF = 0; Static public final int ON = 1; static public final int LOW = 0; Static public final int HIGH = 1; static public final int DEFAULT_TEMP = 72; • Every object in the class has access to the same static variables and constants • A change to a static variable is visible to all of the objects in the class • Examples StaticDemo.java and DemoStatic.java

19. Instance variables // individual object attributes int powerSetting; int fanSetting; int temperatureSetting; • Instance variables are always initialized as soon the object comes into existence • If no value is specified • 0 used for numeric variables • false used for logical variables • null used for object variables • Examples InitializeDemo.java

20. Constructors // AirConditioner(): default constructor public AirConditioner() { this.powerSetting = AirConditioner.OFF; this.fanSetting = AirConditioner.LOW; this.temperatureSetting = AirConditioner.DEFAULT_TEMP; } // AirConditioner(): specific constructor public AirConditioner(int myPower, int myFan, int myTemp) { this.powerSetting = myPower; this.fanSetting = myFan; this.temperatureSetting = myTemp; } • Example AirConditionerConstruction.java

21. Simple mutators // turnOn(): set the power setting to on public void turnOn() { this.powerSetting = AirConditioner.ON; } // turnOff(): set the power setting to off public void turnOff() { this.powerSetting = AirConditioner.OFF; } • Example TurnDemo.java

22. Simple accessors // getPowerStatus(): report the power setting public int getPowerStatus() { return this.powerSetting; } // getFanStatus(): report the fan setting public int getFanStatus() { return this.fanSetting; } // getTemperatureStatus(): report the temperature setting public int getTemperatureStatus () { return this.temperatureSetting; } • Example AirConditionerAccessors.java

23. Parametric mutators // setPower(): set the power setting as indicated public void setPower(int desiredSetting) { this.powerSetting = desiredSetting; } // setFan(): set the fan setting as indicated public void setFan(int desiredSetting) { this.fanSetting = desiredSetting; } // setTemperature(): set the temperature setting as indicated public void setTemperature(int desiredSetting) { this.temperatureSetting = desiredSetting; } • Example AirConditionerSetMutation.java

24. Facilitator toString() // toString(): produce a String representation of the object public String toString() { String result = "[ power: " + this.powerSetting + ", fan: " + this.fanSetting + ", temperature: " + this.temperatureSetting + " ] "; return result; }

25. Sneak peek facilitator toString() public String toString() { String result = "[ power: " ; if ( this.powerSetting == AirConditioner.OFF ) { result = result + "OFF"; } else { result = result + "ON " ; } result = result + ", fan: "; if ( this.fanSetting == AirConditioner.LOW ) { result = result + "LOW "; } else { result = result + "HIGH"; } result = result + ", temperature: " + this.temperatureSetting + " ]"; return result; }

27. ColoredRectangle • Purpose • Represent a colored rectangle in a window • Introduce the basics of object design and implementation

28. Background • JFrame • Principal Java class for representing a titled, bordered graphical window. • Standard class • Part of the swing library import javax.swing.* ;

29. Example • Consider JFrame w1 = new JFrame("Bigger"); JFrame w2 = new JFrame("Smaller"); w1.setSize(200, 125); w2.setSize(150, 100); w1.setVisible(true); w2.setVisible(true);

30. Example • Consider JFrame w1 = new JFrame("Bigger"); JFrame w2 = new JFrame("Smaller"); w1.setSize(200, 125); w2.setSize(150, 100); w1.setVisible(true); w2.setVisible(true);

31. Example • Consider JFrame w1 = new JFrame("Bigger"); JFrame w2 = new JFrame("Smaller"); w1.setSize(200, 125); w2.setSize(150, 100); w1.setVisible(true); w2.setVisible(true);

32. Example • Consider JFrame w1 = new JFrame("Bigger"); JFrame w2 = new JFrame("Smaller"); w1.setSize(200, 125); w2.setSize(150, 100); w1.setVisible(true); w2.setVisible(true);

33. Class ColoredRectangle – initial version • Purpose • Support the display of square window containing a blue filled-in rectangle • Window has side length of 200 pixels • Rectangle is 40 pixels wide and 20 pixels high • Upper left hand corner of rectangle is at (80, 90) • Limitations are temporary • Remember BMI.java preceded BMICalculator.java • Lots of concepts to introduce

34. ColoredRectangle in action • Consider ColoredRectangle r1 = new ColoredRectangle(); ColoredRectangle r2 = new ColoredRectangle(); System.out.println("Enter when ready"); System.in.read(); r1.paint(); // draw the window associated with r1 r2.paint(); // draw the window associated with r2

35. ColoredRectangle in action • Consider ColoredRectangle r1 = new ColoredRectangle(); ColoredRectangle r2 = new ColoredRectangle(); System.out.println("Enter when ready"); System.in.read(); r1.paint(); // draw the window associated with r1 r2.paint(); // draw the window associated with r2

36. ColoredRectangle in action • Consider ColoredRectangle r1 = new ColoredRectangle(); ColoredRectangle r2 = new ColoredRectangle(); System.out.println("Enter when ready"); System.in.read(); r1.paint(); // draw the window associated with r1 r2.paint(); // draw the window associated with r2

37. ColoredRectangle in action • Consider ColoredRectangle r1 = new ColoredRectangle(); ColoredRectangle r2 = new ColoredRectangle(); System.out.println("Enter when ready"); System.in.read(); r1.paint(); // draw the window associated with r1 r2.paint(); // draw the window associated with r2

38. ColoredRectangle.java outline import javax.swing.*; import java.awt.*; public class ColoredRectangle { // instance variables for holding object attributes private int width; private int height; private int x; private int y; private JFrame window; private Color color; // ColoredRectangle(): default constructor public ColoredRectangle() { // ... } // paint(): display the rectangle in its window public void paint() { // ... } }

39. Instance variables and attributes • Data field • Java term for an object attribute • Instance variable • Symbolic name for a data field • Usually has private access • Assists in information hiding by encapsulating the object’s attributes • Default initialization • Numeric instance variables initialized to 0 • Logical instance variables initialized to false • Object instance variables initialized to null

40. public class ColoredRectangle { // instance variables for holding object attributes private int width; private int x; private int height; private int y; private JFrame window; private Color color; // ColoredRectangle(): default constructor public ColoredRectangle() { window = new JFrame("Box Fun"); window.setSize(200, 200); width = 40; x = 80; height = 20; y = 90; color = Color.BLUE; window.setVisible(true); } // paint(): display the rectangle in its window public void paint() { Graphics g = window.getGraphics(); g.setColor(color); g.fillRect(x, y, width, height); } }

41. public class ColoredRectangle { // instance variables for holding object attributes private int width; private int x; private int height; private int y; private JFrame window; private Color color; // ColoredRectangle(): default constructor public ColoredRectangle() { window = new JFrame("Box Fun"); window.setSize(200, 200); width = 40; x = 80; height = 20; y = 90; color = Color.BLUE; window.setVisible(true); } // paint(): display the rectangle in its window public void paint() { Graphics g = window.getGraphics(); g.setColor(color); g.fillRect(x, y, width, height); } }

42. ColoredRectangle default constructor

43. public class ColoredRectangle { // instance variables for holding object attributes private int width; private int x; private int height; private int y; private JFrame window; private Color color; // ColoredRectangle(): default constructor public ColoredRectangle() { window = new JFrame("Box Fun"); window.setSize(200, 200); width = 40; x = 80; height = 20; y = 90; color = Color.BLUE; window.setVisible(true); } // paint(): display the rectangle in its window public void paint() { Graphics g = window.getGraphics(); g.setColor(color); g.fillRect(x, y, width, height); } }

44. Color constants • Color.BLACK • Color.BLUE • Color.CYAN • Color.DARK_GRAY • Color.GRAY • Color.GREEN • Color.LIGHT_GRAY • Color.MAGENTA • Color.ORANGE • Color.PINK • Color.RED • Color.WHITE • Color.YELLOW

46. public class ColoredRectangle { // instance variables for holding object attributes private int width; private int x; private int height; private int y; private JFrame window; private Color color; // ColoredRectangle(): default constructor public ColoredRectangle() { window = new JFrame("Box Fun"); window.setSize(200, 200); width = 40; x = 80; height = 20; y = 90; color = Color.BLUE; window.setVisible(true); } // paint(): display the rectangle in its window public void paint() { Graphics g = window.getGraphics(); g.setColor(color); g.fillRect(x, y, width, height); } }

47. Graphical context • Graphics • Defined in java.awt.Graphics • Represents the information for a rendering request • Color • Component • Font • … • Provides methods • Text drawing • Line drawing • Shape drawing • Rectangles • Ovals • Polygons

48. Java coordinate system

49. public class ColoredRectangle { // instance variables for holding object attributes private int width; private int x; private int height; private int y; private JFrame window; private Color color; // ColoredRectangle(): default constructor public ColoredRectangle() { window = new JFrame("Box Fun"); window.setSize(200, 200); width = 40; x = 80; height = 20; y = 90; color = Color.BLUE; window.setVisible(true); } // paint(): display the rectangle in its window public void paint() { Graphics g = window.getGraphics(); g.setColor(color); g.fillRect(x, y, width, height); } }

50. Method invocation • Consider r1.paint(); // display window associated with r1 r2.paint(); // display window associated with r2 • Observe • When an instance method is being executed, the attributes of the object associated with the invocation are accessed and manipulated • Important that you understand what object is being manipulated