COMP 110 Branching Statements and Boolean Expressions

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COMP 110Branching Statements and Boolean
Expressions

• Tabitha Peck M.S.
• January 28, 2008
• MWF 3-350 pm
• Philips 367

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Announcements

• Program 1 Due Today
• Hand in Pseudocode after class
• Program 2 Assigned Today
• Lab 2 Due Friday

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Questions?
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Today in COMP 110

• Formatting decimals
• Review Worksheet
• If/Else statements
• Boolean Expressions

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Formatting Decimals

• import java.text.
• DecimalFormat df new DecimalFormat("0.00")
• df.format(myVariable)
• Example code on class website

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Review Worksheet

• public class MyProgram
• public static void main(String args)
  String myString This is a string
• int len myString.length()
• System.out.print(the length is len)
• String shortString myString.substring(10)

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Integer division

• Double myDouble (1 / 2) 5.0
• int i 1 / 2

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0.5
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Classes

• Suppose that mary is an object of class Person,
  and suppose that increaseAge is a method of class
  Person that uses one argument, an integer. Write
  the invocation of the method increaseAge for the
  object mary using the argument 5.

Person mary new Person
mary.increaseAge(5)
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Flow Chart
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Flow Chart
Check time if (time lt 7am) take bus else
//time gt 7am take subway Reach school
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Java Example
import java.util. public class FlowChart
public static void main(String
args) System.out.println("Give
me an integer") Scanner keyboard new
Scanner(System.in) int inputInt
keyboard.nextInt() if(
inputInt gt 5)
System.out.println("Big number")
else
System.out.println("Small number")

Start
Prompt User for int
Is user input greater than 5?
NO
YES
Print small number
Print big number
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Java Comparison Operators
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Boolean Expressions

• True of False
• Example expressions
• 5 3
• Variable lt 6
• myInt ! temp
• if (boolean expression)
• statements

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(and)

• What if you need multiple expressions to be true
• (expression) (expression)
• Expressions go in ( )
• Will only be true if ALL statements are true

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(or)

• What if you need ONE expression to be true out of
  many expressions
• (expression) (expression)
• Expressions go in ( )
• Will be true if ONE expression is true

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Gotcha

• var1 var2 (assignment statement)
• Error!!!!!!!
• var1 var2 (boolean expression)
• Do NOT use to compare Strings
• string1 string2 //BAD
• string1.equals(string2) //GOOD

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If Without Else

• You can use just an if statement
• if (boolean expression)
• (statements)
• the rest of your code

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Nested If Else

• if (boolean expression)
• if (boolean expression)
• stuff goes here
• else
• more stuff
• else

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Start
Prompt User for int
What is the integer?
inputInt 0
inputInt gt 1
inputInt 1
Print how may I help you
Print hello
Print how are you
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import java.util. public class FlowChart
public static void main(String
args) System.out.println("Give
me an integer") Scanner keyboard new
Scanner(System.in) int inputInt
keyboard.nextInt() if (
inputInt 0) System.out.println(
hello") else if ( inputInt
1) System.out.println(how are you")
else System.out.println(how may I help you")

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Friday

• Recitation
• Bring Laptop
• Bring Book

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