Flow Control II

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Flow Control II
Qi ZhangSept 8
COMP 110 Introduction to Programming
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Last Class

• Review of Ch.2
• Branching Statement Part I
• The if-else statement
• Boolean expressions
• Nested statements and compound statements

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Todays Lecture

• Branching Statement Part II
• The switch statements
• Loop Statements
• while statement

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Announcements

• Lectures on next Mon Wed
• Lecturer Feng Pan
• Assignment Submission
• Time change
• If assigned on Wed, due on the Wed after two
  weeks, right before class.
• Also bring a printed copy!
• Remember to submit all your files, otherwise, ask
  me to clear your attempt and resubmit
• Talk about Lab 1 on Fri

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Branching Statement Switch

• Multiple Branches

Start
Prompt User for int
What is the integer?
inputInt 0
inputInt is other value
inputInt 1
Print how may I help you
Print hello
Print how are you
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Switch Statements

• switch (inputInt)
• case 1
• System.out.print(how are you)
• break
• case 0
• System.out.print(hello)
• break
• default
• System.out.print(how may I help you)
• break

Controlling expression integer or char ONLY!
Case label
Break statement
Default all other values
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Switch Statements

• Syntax
• switch (controlling expression)
• case case label
• statements
• break
• case case label
• statements
• break
• default
• statements
• break

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In-Class Exercise Practice with Switch statements

• Write a switch statement that takes as
  controlling expression your year in college (as
  int) and outputs your year in college as
  freshman, sophomore, junior, senior, or super
  senior

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Solution

• switch (year)
• case 1
• System.out.print(freshman)
• break
• case 2
• System.out.print(sophomore)
• break
• case 3
• System.out.print(junior)
• break
• case 4
• System.out.print(senior)
• break
• default
• System.out.print(super senior)
• break

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Loop

• How to speedup a car to 100mph?

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Loops

• Loop - part of program that repeats
• Body - statements being repeated
• Iteration - each repetition of body
• Stopping condition

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Types of Loops

• while
• Safest choice
• Not always most elegant
• do-while
• Loop iterates at least ONCE
• for
• Numeric computation changes by equal amount

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while loop
Push the acceleration paddle while (speed is
less than 100mph) push the acceleration
paddle Release the paddle
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while loop

• Syntax
• while (boolean expression)
• statements
• .

Evaluate Boolean Expression
true
false
Execute Body
End loop
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while loop

• The stop condition is a boolean expression. The
  body is repeated if boolean expression is true.
• Speed is less than 100mph
• The statements in the body must be able to change
  the boolean expression value, from true to false.

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while loop
If the Body can not affect the boolean expression
Endless loop !!
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In-Class exercise

• Use while loop to describe how to output integer
  number from 1 to 10.
• Draw flow chart
• Write pseudocode
• n1
• output n
• nn1
• output n
• nn1
• output n
• ..
• until n10

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In-Class exercise
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In-Class exercise

• int n 1
• while (nlt 10)
• Output n
• n n1

int n 1 while (nlt10) System.out.println(n)
nn1
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Assignment 2

• Due time 9AM Sept 24
• Submission
• through Blackboard
• Print out and turn in during class