Loops, Conditionals, Scope

1
Loops, Conditionals, Scope

• new
• 2) primitive
• 3) /Many possible answers see below for
  examples/
• int numEnrolled
• double gpaBoost
• boolean isAP
• String courseName
• 4) apCompSciAPer1.add(Larry Jones)
• 5) String greeting Hello there! // or new
  String(Hello)
• String badWord greeting.substring(0,4)
• String capitalGreeting greeting.toUpperCase
  ()
• 6) Encapsulation

2
Boolean expressions

• Any expression that can be simplified to true or
  false.
• Often use
• lt gt lt gt, , !
• , , !
• Example
• x gt -2 x lt 10
• or
• (x gt -2) (x lt 10)
• (Use parentheses for clarity)

3
If statements

• if (x gt 0)
• y Math.sqrt(x)
• else
• System.out.println(Error cannot take
  the square root of a negative number.)
• if (agegt0 age lt 18)
• prsn.setMinor(true)
• if (age gt 16)
• prsn.setCanDrive(true)
• else
• prsn.setCanDrive(false)
• if (age gt 18)
• if (prsn.getIsCitizen())
• prsn.setCanVote(true)
• else
• prsn.setCanVote(false)

4
if-else statements

• if (x lt 0)
• System.out.println(x is negative)
• else if (x gt 0)
• System.out.println(x is positive)
• else
• System.out.println(x is zero.)

5
while loops

• What is the output of the following code segment?
• int x 12
• int y 1
• while (x gt 0)
• x - y
• y
• System.out.println(xy)
• Output 3

6
while loops

• What is the output of the following code segment?
• int x -1
• int y 3
• while (x gt 0)
• x - y
• y
• System.out.println(xy)
• Output 2

7
while loops

• What does this loop do?
• int mystryNum (int)100Math.random() 1
• boolean finished false
• while (!finished)
• if (mystryNum 2 0)
• mystryNum / 2
• else
• finished true

8
do-while loops

• What is the output of the following code segment?
• int x -1
• int y 3
• do
• x - y
• y
• while (x gt 0)
• System.out.println(xy)
• Output 0

9
Variable Scope

• Scope
• the inner-most block of code in which a variable
  is defined.
• The variable does not exist outside this block.
• The garbage-collector erases variables as soon as
  they fall out-of-scope.

• int x 1
• while (x lt 10)
• int y 2
• if (x gt y)
• int z x y
• y z
• else
• x z

Output Compiler error cannot find symbol
variable z
10
Variable Scope

• What is the output of the following code segment?
• int x 0
• while (x lt 10)
• int y 2
• x y
• y
• System.out.println(y)
• Output Compiler Error
• cannot find symbol variable y

11
Variable Scope

• What is the output of the following code segment?
• int x 0
• while (x lt 10)
• int y 2
• x y
• y
• System.out.println(x)
• Output 10

12
for loops

• int sum 0
• for (int x 0 x lt 20 x)
• sum x
• System.out.println(sum)
• Output 190

Declarations Initializations
Condition for continuation
Adjustment after each loop
int x 0
for (
x lt 20
x
)
13
for loops

• What is the output of the following code segment?
• for (int x0 x lt 10 x)
• x x
• System.out.println(x)
• Output Compiler error
• symbol not found
• variable x

14
for loops

• What is the output of the following code segment?
• int x 0
• for (int y0 x lt 10 yx)
• x y
• System.out.println(x)
• Output Runtime error infinite loop!

15
for loops

• What is the output of the following code segment?
• int x 0
• int y
• for (y0 x lt 10 y)
• x y
• System.out.println(xy)
• Output 15