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Java Applets for Experiments

Java Applets for Experiments. NSF Workshop, UC-Fullerton Gary McClelland 10-13 August 2003. Java Workshop Outline. Java, what it is and isn’t Object-Oriented Programming (OOP) First applet: HelloWorld Graphics drawing Listening for events mouse, keys, Buttons, Scrollbars.

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Java Applets for Experiments

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  1. Java Applets for Experiments NSF Workshop, UC-Fullerton Gary McClelland 10-13 August 2003

  2. Java Workshop Outline • Java, what it is and isn’t • Object-Oriented Programming (OOP) • First applet: HelloWorld • Graphics drawing • Listening for events • mouse, keys, Buttons, Scrollbars

  3. Java ≠ Javascript • Javascript • HTML scripting language • Forms • Interpreted • Java • Applets embedded in HTML page • Standalone applications • Complete programming language • Compiled

  4. Java’s Goods & Bads • Strengths • Graphics • Interactivity (mouse, keys, scrollbars) • Precise control • Weaknesses • Timing at the ms level (some debate) • Learning curve

  5. History of an Applet • Edit java source code & html • notepad Hello.java • notepad Hello.html • Compile source to ByteCodes • javac Hello.java • produces Hello.class • View applet (Java Virtual Machine) • appletviewer Hello.html • browser Hello.html

  6. Integrated Development Environment (IDE): JBuilder • Editor • Syntax checking • Command completion • Automatic compilation • HTML Viewer • Switch form editor to browser view

  7. <html> <body> <applet code=“Hello.class” width=“300” height=“300”> </applet> </body> </html>

  8. Object-Oriented Programming (OOP) • Objects • State Variables • Behavior Methods • Car • State: running, speed, location • Behavior: brake, accelerate, changeGear, start, stop

  9. Java class: object blueprint • Class variables • Constructor (object “factory”) • Methods (subroutine definitions)

  10. Inheritance

  11. Interface • Car • Brake pedal • Gas pedal • Steering wheel • Turn signal lever • MouseMotionListener • public void mouseMoved(MouseEvent me) • public void mouseDragged(MouseEvent me)

  12. Encapsulation • Car • How brakes and engine work can be a mystery • Java Object • private methods • We don’t need to know how they work

  13. Card Constructor • Card(String s1, Color c1, String s2, Color c2, int fontSize) • s1: text on “front” of card • c1: color on “front” of card • s2: text on “reverse” of card after click • c2: color on “reverse” of card after click • fontSize: size of font for both Strings

  14. Card Object As Loaded After Click add(new Card(“front”,Color.blue,“reverse”, Color.red, 14));

  15. Using Card in Wason Task public void init() { setLayout(new GridLayout(1,4,20,0)); add(new Card("E",Color.white,"E",Color.yellow,24)); add(new Card("K",Color.white,"K",Color.yellow,24)); add(new Card("4",Color.white,"4",Color.yellow,24)); add(new Card("5",Color.white,"5",Color.yellow,24)); repaint(); }

  16. Wason Task with Feedback public void init() { setLayout(new GridLayout(1,4,20,0)); add(new Card("E",Color.white,"E",Color.green,24)); add(new Card("K",Color.white,"K",Color.red,24)); add(new Card("4",Color.white,"4",Color.red,24)); add(new Card("5",Color.white,"5",Color.green,24)); repaint(); }

  17. Diagnosis Task with 400 Cards

  18. Diagnosis Task after Sampling

  19. Diagnosis Code public void init() { int rows = 20; int cols = 20; int n = rows * cols; int pos = (38*n)/100; //38% of tests are positive int neg = n - pos; setLayout(new GridLayout(rows,cols,5,5)); int cpos = (80*pos)/100; //80% of pos are true pos int cneg = pos - cpos; for(int i=1; i<=pos; i++) { if(Math.random() < (double)cpos/(double)(cpos+cneg)) { add(new Card("M+",Color.yellow,"C+",Color.red,12)); cpos = cpos - 1; } else { add(new Card("M+",Color.yellow,"C-",Color.green,12)); cneg = cneg - 1; } }

  20. Diagnosis Code, Part 2 cpos = (20*pos)/100; //20% of negs are false pos cneg = neg - cpos; for(int i=pos+1; i<=n; i++) { if(Math.random() < (double)cpos/(double)(cpos+cneg)) { add(new Card("M-",Color.white,"C+",Color.red,12)); cpos = cpos - 1; } else { add(new Card("M-",Color.white,"C-",Color.green,12)); cneg = cneg - 1; } } repaint(); }

  21. Your Turn! • Your first applet • “Hello World”

  22. History of an Applet • Edit java source code & html • notepad Hello.java • notepad Hello.html • Compile source to ByteCodes • javac Hello.java • produces Hello.class • View applet (Java Virtual Machine) • appletviewer Hello.html • browser Hello.html

  23. <html> <body> <applet code=“Hello.class” width=“300” height=“300”> </applet> </body> </html>

  24. <html> <body> <applet code=“Hello.class” width=“300” height=“300”> </applet> </body> </html> Save as Hello.html

  25. import java.awt.Applet; public class Hello extends Applet { public void init() { repaint(); } public void paint(Graphics g) { g.drawString(“Hello World!”,30,30); } }

  26. import java.awt.Applet; public class Hello extends Applet { public void init() { repaint(); } public void paint(Graphics g) { g.drawString(“Hello World!”,30,30); } } Save as Hello.java

  27. History of an Applet • Edit java source code & html • notepad Hello.java • notepad Hello.html • Compile source to ByteCodes • javac Hello.java • produces Hello.class • View applet (Java Virtual Machine) • appletviewer Hello.html • browser Hello.html

  28. History of an Applet • Edit java source code & html • notepad Hello.java • notepad Hello.html • Compile source to ByteCodes • javac Hello.java • produces Hello.class • View applet (Java Virtual Machine) • appletviewer Hello.html • browser Hello.html

  29. Graphics Object g (0,0) (x,y) (width,height)

  30. Graphics Methods: Size • getSize().width; • int wd = getSize().width; • getSize().height; • int ht = getSize().height; • g.drawRect(0,0,wd,ht); • draws largest possible rectangle • g.drawString(“Center”,wd/2, ht/2);

  31. Graphics Methods: Shapes • g.drawRect(x,y,w,h); • g.fillRect(x,y,w,h); • g.drawOval(x,y,w,h); • g.fillOval(x,y,w,h); • g.drawLine(x1,y1,x2,y2);

  32. Graphics: More Shapes • g.drawPolygon(xPts,yPts,nPts); • g.fillPolygon(xPts,yPts,nPts); • g.drawArc(x,y,w,h,startAngle,endAngle); • g.fillArc(x,y,w,h,startAngle,endAngle);

  33. Graphics Methods: Colors • g.setColor(Color.black); • Color.red, Color.blue, Color.green, Color.orange, Color.magenta, others… • g.setColor(new Color(r, g, b)); • 0 ≤ r ≤ 255 • 0 ≤ g ≤ 255 • 0 ≤ b ≤ 255 • setBackground(Color.yellow);

  34. Graphics Methods: Fonts • g.setFont(new Font(font, style, size)); • Fonts: “Helvetica” “Courier” “Times” • Style: Font.PLAIN, Font.BOLD, Font.ITALIC • Size: any integer • g.drawString(string, x, y);

  35. FontMetrics • FontMetrics fm; • fm=getFontMetrics(getFont()); • int len = fm.stringWidth(“Center”); • int fht = fm.getHeight(); • g.drawString(“Center”, wd/2-len/2, ht/2+fht/2);

  36. Arrays • int x[] = new int[3]; • Note: arrays start at 0 • Above creates x[0], x[1], x[2] • double y[] = new double[5]; • Card cards[][]; • cards = new Card[20][10]; • cards[2][3] = new Card();

  37. Control Structures if (logical statement) { } else { } for(int i=1; i<=n; i++) { }

  38. Widgets • Button • Scrollbar • TextField • ChoiceList • Menu • Checkbox

  39. MouseListener • Object implements an interface • public class MouseDemo extends Applet implements MouseListener { • Object registers to listen for events • addMouseListener(this);

  40. MouseListener Methods • Object must have these methods • public void mouseClicked(MouseEvent me) • public void mousePressed(MouseEvent me) • public void mouseReleased(MouseEvent me) • public void mouseEntered(MouseEvent me) • public void mouseExited(MouseEvent me)

  41. MouseEvent methods • getX() • getY() • getPoint() • getWhen()

  42. Saving Data via cgi //send data to server //data saved locally in String dataString; public void recordData() {try { Socket t = new Socket("samiam.colorado.edu",80); DataOutputStream out = new DataOutputStream(t.getOutputStream());

  43. Constructing (Faking) POST out.writeBytes( "POST "+ "http://www.myuni.edu/scripts/saveData.cgi" + " HTTP/1.0\r\n"); out.writeBytes( "Content-type: application/octet-stream\r\n"); out.writeBytes( "Content-length: " + dataString.length() + "\r\n\r\n"); out.writeBytes(dataString);

  44. Remainder of recordData() t.close(); //close Socket to server } catch(IOException e) {System.out.println("Error" + e); } } }

  45. recordData() complete public void recordData() { //send data to server try { Socket t = new Socket(”www.myuni.edu",80); DataOutputStream out = new DataOutputStream(t.getOutputStream()); out.writeBytes( "POST "+ "http://www.myuni.edu/scripts/saveData.cgi"+ " HTTP/1.0\r\n"); out.writeBytes("Content-type: application/octet-stream\r\n"); out.writeBytes( "Content-length: " + dataString.length() + "\r\n\r\n"); out.writeBytes(dataString); t.close(); } catch(IOException e) {System.out.println("Error" + e); } } }

  46. Object-Oriented Javascript • Properties • ;ocation • name • value • opener • Methods • open() • close() • write() • submit() • Objects • Window • Document • Frame • Form • RadioButton • Link • URL

  47. Object Syntax • object.property • car.speed [= 30 mph] • window.location [current URL] • object.method() • car.accelerate(40) [speed up to 40 mph] • window.close() [close this window]

  48. StoryMaker Illustrates: • Constructing web pages on the fly • Invisible to search engines • Control experiment flow • (e.g., no back button) • Pop-up windows • Dialog boxes • Hints • Instructions

  49. Tree of “StoryMaker” • document • writeStory (function) • storyInfo (form) • nn (textbox for name) • value • birth (textbox for birth place) • value • Sex[0] (radio button for male) • checked • Sex[1] (radio button for female) • checked

  50. StoryMaker continued • storyInfo (form, continued) • color (Select menu) • Length • value • selectedIndex • options[0] (“Red”) • options[1] (“Green”) • …… • options[4] (“Blanced Almond”)

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