Counter Practical whats going on

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Counter Practicalwhats going on?

• David Corsar
• dcorsar_at_csd.abdn.ac.uk

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Last week

• Last week we looked at how to
• Use rectangle as a supplier class for displaying
  a rectangle and getting it to change colour
• Use 2 supplier classes (MovingSun and Oval) in
  the Sun Picture practical, and combine with a
  simple controller class (SunPicture) which tells
  MovingSun what to do

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Counter Practical

• We also started the Counter practical, today we
  will look at how it works

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Counter practical Classes
Makes the 3 digit counter, tells each digit to
increment, decrement, makeZero where appropriate
Displays a Digit of the counter
Controller class provides window for Counter to
display and tells it what to do depending on
button press
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor

public CounterWindow() window new
ThreeButtonFrame("Counter") counter new
Counter(window)
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor
• CounterWindow initialises counter to a new
  Counter instance

public CounterWindow() window new
ThreeButtonFrame("Counter") counter new
Counter(window)
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor
• CounterWindow initialises counter to a new
  Counter instance
• Counter then initialises its 3 Digits

public Counter(JFrame frame) units new
Digit(..., frame) tens new Digit(...,
frame) hundreds new Digit(..., frame)
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor
• CounterWindow initialises counter to a new
  Counter instance
• Counter then initialises its 3 Digits

public Counter(JFrame frame) units new
Digit(..., frame) tens new Digit(...,
frame) hundreds new Digit(..., frame)
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor
• CounterWindow initialises counter to a new
  Counter instance
• Counter then initialises its 3 Digits

public Counter(JFrame frame) units new
Digit(..., frame) tens new Digit(...,
frame) hundreds new Digit(..., frame)
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor
• CounterWindow initialises counter to a new
  Counter instance
• Counter then initialises its 3 Digits

public Counter(JFrame frame) units new
Digit(..., frame) tens new Digit(...,
frame) hundreds new Digit(..., frame)
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor
• CounterWindow initialises counter to a new
  Counter instance
• Counter then initialises its 3 Digits

public Counter(JFrame frame) units new
Digit(..., frame) tens new Digit(...,
frame) hundreds new Digit(..., frame)
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor
• CounterWindow initialises counter to a new
  Counter instance
• Counter then initialises its 3 Digits

public Counter(JFrame frame) units new
Digit(..., frame) tens new Digit(...,
frame) hundreds new Digit(..., frame)
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor
• CounterWindow initialises counter to a new
  Counter instance
• Counter then initialises its 3 Digits

public Counter(JFrame frame) units new
Digit(..., frame) tens new Digit(...,
frame) hundreds new Digit(..., frame)
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What happens when it runs

• Load BlueJ, create new CounterWindow
• BlueJ creates a new instance of CounterWindow,
  calling its Constructor
• CounterWindow initialises counter to a new
  Counter instance
• Counter then initialises its 3 Digits
• Everything is set up ready to be used

public CounterWindow() window new
ThreeButtonFrame("Counter") counter new
Counter(window)
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What happens when it runs

• User clicks right button, calls rightAction on
  CounterWindow

public void rightAction()
counter.increment()
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What happens when it runs

• User clicks right button, calls rightAction on
  CounterWindow

public void rightAction()
counter.increment()
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What happens when it runs

• Increment tells the relevant digits to increment
• Lets say units 9, tens 9, hundreds 0,

public void increment() units.increment() if
(units.getValue() 10) units.makeZero() tens.i
ncrement() if (tens.getValue()
10) tens.makeZero() hundreds.increment() if
(hundreds.getValue() 10) makeZero()
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What happens when it runs

• Increment tells the relevant digits to increment
• now units 10, tens 9, hundreds 0,

public void increment() units.increment() if
(units.getValue() 10) units.makeZero() tens.i
ncrement() if (tens.getValue()
10) tens.makeZero() hundreds.increment() if
(hundreds.getValue() 10) makeZero()
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What happens when it runs

• Increment tells the relevant digits to increment
• now units 10, tens 9, hundreds 0,

public void increment() units.increment() if
(units.getValue() 10) units.makeZero() tens.i
ncrement() if (tens.getValue()
10) tens.makeZero() hundreds.increment() if
(hundreds.getValue() 10) makeZero()
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What happens when it runs

• Increment tells the relevant digits to increment
• now units 0, tens 9, hundreds 0,

public void increment() units.increment() if
(units.getValue() 10) units.makeZero() tens.i
ncrement() if (tens.getValue()
10) tens.makeZero() hundreds.increment() if
(hundreds.getValue() 10) makeZero()
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What happens when it runs

• Increment tells the relevant digits to increment
• now units 0, tens 10, hundreds 0,

public void increment() units.increment() if
(units.getValue() 10) units.makeZero() tens.i
ncrement() if (tens.getValue()
10) tens.makeZero() hundreds.increment() if
(hundreds.getValue() 10) makeZero()
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What happens when it runs

• Increment tells the relevant digits to increment
• now units 0, tens 10, hundreds 0,

public void increment() units.increment() if
(units.getValue() 10) units.makeZero() tens.i
ncrement() if (tens.getValue()
10) tens.makeZero() hundreds.increment() if
(hundreds.getValue() 10) makeZero()
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What happens when it runs

• Increment tells the relevant digits to increment
• now units 0, tens 0, hundreds 0,

public void increment() units.increment() if
(units.getValue() 10) units.makeZero() tens.i
ncrement() if (tens.getValue()
10) tens.makeZero() hundreds.increment() if
(hundreds.getValue() 10) makeZero()
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What happens when it runs

• Increment tells the relevant digits to increment
• now units 0, tens 0, hundreds 1,

public void increment() units.increment() if
(units.getValue() 10) units.makeZero() tens.i
ncrement() if (tens.getValue()
10) tens.makeZero() hundreds.increment() if
(hundreds.getValue() 10) makeZero()
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What happens when it runs

• Increment tells the relevant digits to increment
• now units 0, tens 0, hundreds 1
• Now finished with increment and rightAction
• Waiting for next click