Eliza java code

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Eliza java code
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applets

• ElizaApplet.java is an applet (rather than a
  regular java program)
• there is no method called main( )
• instead, the applet is started when the
  ElizaApplet.html page is opened

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Eliza.html

• lthtmlgt
• ltheadgt
• lttitlegtElizaAppletlt/titlegt
• lt/headgt
• ltbodygt
• ltapplet codebase "." code "ElizaApplet.class"
  width 400 height 400gtlt/appletgt
• lt/bodygt
• lt/htmlgt

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ElizaApplet.java

• the init method of ElizaApplet.java is invoked
  when Eliza.html is opened
• init creates an object eliza, which is an
  instance of the class MyEliza
• init sets up a text area (elizaOutput) for the
  conversation, and a text field (elizaInput) where
  the user enters input
• the applet must be able to respond to input events

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responding to inputs

• the ElizaApplet class implements ActionListener
  which gives objects of the class the ability to
  respond to inputs from the user
• the class must have a corresponding
  actionPerformed method, which specifies how the
  program responds to inputs

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public void actionPerformed(ActionEvent e)

• if (e.getSource()elizaInput)
• //what happens if the user presses enter
• elizaOutput.append("gtgt " elizaInput.getText()
  "\n eliza.grabText((elizaInput.getText()).toL
  owerCase()) "\n")
• elizaInput.setText("")

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thats it for ElizaApplet!
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myEliza.java

• what happens when the instruction
• eliza new MyEliza( )
• is executed as part of the ElizaApplet code?

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myEliza.java

• what happens when the instruction
• eliza new MyEliza( )
• is executed as part of the ElizaApplet code?
• - the object eliza is created, and its
  variables greeting, qa, unknowns, and polly are
  initialized

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unknowns

• what type of object is unknowns?
• what does unknowns look like, when it is
  initialized?

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qa

• what type of object is qa?
• what methods does this type of object have?
• what does qa look like once it is initialized?

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grabText

• public String grabText(String said)
• StringTokenizer patient
• String theAnswer String curr
• theAnswer""
• more code here to calculate Elizas
  response to said
• return theAnswer

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calculating Elizas response

• the string said is broken up into an ordered list
  of words (tokens), part of an object called
  patient
• if one of the tokens is a keyword, then respond
  with the corresponding response in the hashtable
  and otherwise choose a random generic response

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tokenizing the string said

• example
• said my mother asked about my classes
• the tokenized version of said
• patient my, mother, asked, about,
  my classes

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patient a StringTokenizer Object

• this object has methods
• nextToken removes the next token from and
  returns it
• hasMoreTokens returns true or false, depending
  on whether there are tokens left

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calling StringTokenizer methods

• initially,
• patient is my, mother, asked, about,
  my classes
• after three invocations of patient.nextToken,
• patient is about, my classes
• and patient.hasMoreTokens() is true
• what about after three more invocations?

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calculating the answer

• patient new StringTokenizer(said)
• while (patient.hasMoreTokens()
  theAnswer.equals(""))
• curr patient.nextToken()
• if (qa.containsKey(curr))
• theAnswer (String)qa.get(curr)
• if (theAnswer.equals(""))
• theAnswerunknownsgimme_a_number()