Announcements%20

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Announcements Review

• Last Time
• Beauty
• Repetition
• for - the iterated loop in Java

• Announcements
• Discussion Sections PAI 5.70, quiz excercise,
  problem available at 9am, due 10pm Tuesday
• Reading Ch 1-4, Regis and Stepp on-line
• Lab 1 Due Thursday 10pm

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Today

• More basic program elements
• Types
• Variables
• Operators
• Conditional execution
• if (condition)
• // true action
• else
• // false action

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Programming Elements

• Type
• Set of values and operators that create and
  manipulate values from the set
• Values primitive types
• numeric
• double and float (size)
• Values with decimals
• int, byte, short, long (size)
• Integers
• Character char
• Characters (considered numeric)
• Boolean boolean
• Logical values

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Operators, Constants, Variables

• Basic operators
• addition - subtraction
• multiplication / division
• Constant
• Symbolic name for memory location whose value
  does not change
• final int MAX_HEART_RATE 220
• Variable
• Symbolic name for memory location whose value can
  change
• int age

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Some declarations operations

• // Computes target heart rate
• // final means the program can never change it
• final int MAX_HEART_RATE 220
• int age 18
• // target heart rates
• int aerobicZone, fatBurningZone
• aerobicZone MAX_HEART_RATE - age .75
• fatBurningZone MAX_HEART_RATE - age .65

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BlueJ Examples

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A boolean type

• Java has the logical type boolean
• Type boolean has two literal constants
• true
• false
• Operators
• The and operator is
• The or operator is
• The not operator is !

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Defining boolean variables

• Local boolean variables are uninitialized by
  default
• boolean isWhitespace
• boolean receivedAcknowledgement
• boolean haveFoundMissingLink

-
isWhitespace
-
receivedAcknowledgement
-
haveFoundMissingLink
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Defining boolean variables

• Local boolean variables with initialization
• boolean canProceed true
• boolean preferCyan false
• boolean completedSecretMission true

true
canProceed
false
preferCyan
true
completedSecretMission
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Truth tables

• formal specifications of operators
• It works as most of us would expect allows for
  ambiguity of interpretation
• Jim is smiling or Patty is smiling
• Can both Jim and Patty be smiling?
• Truth tables
• Lists all combinations of operand values and the
  result of the operation for each combination

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And, Or, Not truth tables
p not p
False True True False
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Boolean algebra

• Can create complex logical expressions by
  combining simple logical expressions
• not (p and q)

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DeMorgans laws

• not (p and q) equals (not p) or (not q)

not (not p) or p q p and q (p
and q) ( not p) (not q) ( not q)
False False False True True
True True False True False True
True False True True False
False True False True
True True True True False False
False False
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Conditionals

• Conditional expression must evaluate to the
  boolean value true
• int x, y // compute max
• if (x gt y)
• max x
• else // x lt y
• max y

boolean next false if (next)
...println(May I help you?)
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BlueJ Examples

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More Questions?