Week 5

BYTE FROM COMPUTING HISTORY
In 1987, computer scientist Anita Borg
combined technical expertise with a
vision to inspire, motivate, and
encourage women in technology. She
founded a digital community for women
in computing.
Read more about her mission.
2

YOU CAN DO IT!
3
• There is no geek gene!
• You are capable of learning
programming with motivation and
proper practice.
• You can apply computing in your
chosen career: Art, Film, Biology,
Math, Physics, Astronomy…...

CONGRATULATIONS ON THE SKILLS YOU HAVE GAINED!
Analysis - Problem Solving
Design - Creativity
Coding - Computational Thinking
Testing - Rigour
Debugging - Persistence
4

GOALS FOR TODAY’S CLASS
More nuts & bolts of programming!
• More if-else
• Conditional expressions
• Logical Operators
• Short circuit evaluations
• Boolean data types
5

REVIEW - IF-ELSE STATEMENTS
6
An if-else statement executes one group of statements when an
expression is true, and another group of statements when the
expression is false.

EXAMPLE PROBLEM
Write a program that checks the user age and prints
"Enjoy your early years." if the user is less than 16 years.
It prints "You are old enough to drive." if the user is over
the age of 15 but less than 17 years of age. It prints "You
are old enough to vote." if the user is over 17 years of age
but less 24 years of age. It prints "Most car rental
companies will rent to you." if the user is over the age of
24 but less than 34 years of age. If the user is over the
age of 34, it prints "You can run for president.".
7

FLOW CHART
FOR EXAMPLE
PROBLEM
9

EXAMPLE CODE
10
May print
multiple
statements

REVIEW: NESTED IF-ELSE
Branch statements can include another if-else statement.
11
Draw a
flowchart

CLICKER QUESTION 1
12
salesType = 2;
salesBonus = 7;
What is the the final
value of
salesBonus?
A. 7
B. 8
C. 9
D. 10

CLICKER QUESTION 1 ANSWER
13
salesType = 2;
salesBonus = 7;
What is the the final
value of salesBonus?
A. 7
B. 8
C. 9
salesBonus is 7 + 2, or 9
D. 10
TRUE
TRUE
FALSE

CLICKER QUESTION 2
14
A. Annual price: $2100
B. Annual price: $2350
C. Annual price: $0
D. Annual price: $4800
What is the output of the code if the age of the user is 46?

15
What is the output of the code
if the age of the user is 46?
A. Annual price: $2100
B. Annual price: $2350
C. Annual price: $0
D. Annual price: $4800
Note
age
ranges

REVIEW: EQUALITY AND RELATIONAL OPERATORS
16
Equality operator checks whether two operands' values are the same
(==) or different (!=). Note that equality is ==, not just =
Relational operator checks how one operand's value relates to another
e.g. being greater than.

CLICKER QUESTION 3
A. 5 is greater than 3
B. 5 is not greater than 3
C. 3 is not greater than 5
D. Error
17

A. 5 is greater than 3
B. 5 is not greater than 3
C. 3 is not greater than 5
D. Error
18
>=

LOGICAL OPERATORS
&& and
|| or
! Not
1. x > 0 && x < 10 is true (when x is greater
than zero AND less than 10)
2. isEven || n % 2 == 0 is true (if EITHER
condition is true)
3. !isEven is true (if isEven is NOT true.)
19

BOOLEAN DATA TYPE
Boolean variable may be set
using true or false keywords.
20
Don't have to write if (evenFlag == true)

CLICKER QUESTION 4
boolean var1 = true;
boolean var2 = false;
System.out.println((var2 && var1));
21
A. 0
B. 1
C. true
D. false
E. error

boolean var1 = true;
boolean var2 = false;
System.out.println((var2
&& var1));
22
A. 0
B. 1
C. true
D. false
E. error

TERNARY OPERATOR - CONDITIONAL EXPRESSIONS
23
condition ? exprWhenFalse.
exprWhenTrue :
NOTE: ()
around first
expression

SHORT CIRCUIT EVALUATION
Only evaluates the second operand if necessary.
true || anything is always true
false && anything is always false
!(A && B) is the same as !A || !B
!(A || B) is the same as !A && !B
!(x < 5 && y == 3) is the same as x >= 5 || y != 3
If I don't want the case where x is less than 5 AND y is 3, then I need
x to be greater than OR equal to 5, or I need y to be anything but 3.
24
De Morgan's laws

CLICKER QUESTION 5
((x > 2) || (y < 4)) && (z == 10)
Given x = 4, y = 1, and z = 10, which
comparisons are evaluated?
A. Error
B. (x>2), (y<4) and (z==10)
C. (x>2) and (z==10)
D. (x>2) and (y <4)
25

CLICKER QUESTION 5
((x > 2) || (y < 4)) && (z == 10)
Given x = 4, y = 1, and z = 10, which
comparisons are evaluated?
A. Error
B. (x>2), (y<4) and (z==10)
C. (x>2) and (z==10)
D. (x>2) and (y <4)
26
(4 > 2) is true
so OR operator
evaluates to true
(z == 10) is
evaluated to
determine ﬁnal
result.

GOOD PROGRAMMING PRACTICES
1. Design before you code- i.e. think and plan what you
will code first.
2. Don’t write all of the code at once. Implement the
outline, or “skeleton” of the code.
3. Incremental development- fill in the smaller parts one
at a time. Debug and test the smaller parts before
moving on.
4. Use the debugger- integral part of development.
27

TO-DO LIST:
• Check your iClicker grades in Moodle.
• Complete zyBook chapter 4-5 exercises.
• Communicate with us using only Moodle forum or
Piazza.
• Upload Project 2 before the deadline!
28

GOALS FOR TODAY’S CLASS
Demo: PROJECT 3
More nuts & bolts of programming!
• String and Character operations
• Switch statement
• String comparisons and character access
2

REVIEW: RANDOM CLASS
3
You can also pass a
programmer-deﬁned range.
See zyBooks 4.10.

PROJECT 3 OVERVIEW
Note: 2 constructors
Note: private method
4

0, 1, 2
PROJECT 3 OVERVIEW
5
Given the output of a random number generator, how
can you translate that output to Strings such as “A”,
“B”, “C”, where each String is equally likely?
0, 1, 2, 3, 4, 5, 6, 7, 8
“A”, “B”, “C” “A”, “B”, “C”
Easier:
3 ints
generated.
9 ints
generated.

PROJECT 3 MAIN CLASS
1. Creates new instance of StickWaterFireGame called
game.
2. Sets up Scanner and prompts user.
3. Calls methods getScoreReportStr(),
playerWinning(), getComputerChoice(),
computerWinning(), isTie() playRound()
4. Prints messages to player
6
1. Cannot access
private method
getRandomChoi
ce()
2. Does not call
isValidInput
- which is called
internally only by
playRound.

IMPORTANT REMINDERS FOR PROJECTS
1. Start early.
2. Submit often in Gradescope.
3. Keep track of the deadline and grace period to
submit to Gradescope.
4. Attend office hours or ask for help in Piazza (no
showing code).
5. Use the debugger.
6. Read the Tips & FAQs doc and other resources in
Moodle.
7. Use a search engine and/or Java API. 7

TIP: WRITING CONCISE
STATEMENTS
Instead of writing
multiple return
statements you
should
1. declare a variable,
2. set its value
according to the
condition,
3. and use 1 return
statement.
8
Example from a
previous project.

SWITCH WITH BREAK: EXAMPLE
10
switch(grade) {
case 'A' :
System.out.println("Excellent!");
break;
   case 'B' :
   case 'C' :
System.out.println("Well done");
break;
   case 'D' :
System.out.println("You passed");
   case 'F' :
System.out.println("Better try again");
break;
   default :
System.out.println("Invalid grade");}
System.out.println("Your grade is " + grade);
End
Switch
Break statement

SWITCH STATEMENT- KEEP IN MIND
• Duplicate case values are not allowed.
• The value for a case must be the same data type as the
variable in the switch.
• The value for a case must be a constant or a literal.
Variables are not allowed.
• The break statement is used inside the switch to terminate
a statement sequence.
• The break statement is optional. If omitted, execution will
continue on into the next case.
• The default statement is optional, and it must appear at the
end of the switch.
11

CLICKER QUESTION 1
A. User wants to visit Corfu
User wants to visit Crete
B. User wants to visit Crete
C. Unknown Island
D. User wants to visit Corfu 12
What is the output?

A. User wants to visit Corfu
User wants to visit Crete
B. User wants to visit Crete
C. Unknown Island
D. User wants to visit Corfu
E. Error 13
switch(island) {
case "Corfu":
   System.out.println("User wants to visit Corfu");
case "Crete":
   System.out.println("User wants to visit Crete");break;
case "Santorini":
   System.out.println("User wants to visit Santorini");break;
default:
   System.out.println("Unknown Island");}
String island = "Corfu";
2 statements printed
as missing break
after first case.

CHARACTER CLASS STATIC METHODS
Character.isDigit
Character.isLetter
Character.isLetterOrDigit
Character.isLowerCase
Character.isUpperCase
Character.isWhitespace
Character.toLowerCase
Character.toUpperCase
14
● Must use
Character.method
Name
● Static methods do not
need objects to be
created.
● All methods return
values.

CHARACTER CLASS: EXAMPLES - T-P-S
15
char value1 = '9';
System.out.println(Character.isDigit(value1));

char value2 = '*';
System.out.println(Character.isLetterOrDigit(value2));
char value3 = ';';
System.out.println(Character.isLetter(value3));
char value4 = ' ';
System.out.println(Character.isLetter(value4));
All functions evaluate to TRUE or FALSE

STRING ACCESS: RECALL
Each string character has a position number called
an index, starting with 0 (not 1)
String pupName = “Spot”;
char ch = pupName.charAt(1);
// ch is assigned ‘p’
ch = pupName.charAt(0);
// ch is assigned ‘S’ 16

CHARACTER CLASS: EXAMPLE
17
String str = “Cheese”;
char char1 = str.charAt(1);
h
char char2 = Character.toUpperCase(char1);
H
Each character in a String has an index number.

CLICKER QUESTION 2
18
Consider this string:
String str = “Hi 357 times!!”;
Which one of the following returns true?
A. Character.isWhitespace(str.charAt(6));
B. Character.isDigit(str.charAt(6));
C. Character.isLetter(str.charAt(5));
D. Character.isLowerCase(str.charAt(0));

CLICKER QUESTION 2 - ANSWER
19
String str = “Hi 357 times!!”;
Which one of the following returns True?
A. Character.isWhitespace(str.charAt(6));True
B. Character.isDigit(str.charAt(6)); False
C. Character.isLetter(str.charAt(5)); False
D. Character.isLowerCase(str.charAt(0)); False

WORKING WITH STRINGS
PROBLEM: Find the last character in the string
“Supercalifragilisticexpialidocious”.
SOLUTION: Find the character at length of string -1.
20
Also written as above.

CLICKER QUESTION 3
21
Consider these statements about a String called str:
Character.isLetter(str.charAt(5)); True
Character.toUpperCase(str.charAt(10)); A
Character.isWhitespace(str.charAt(13)); True
Which one of the following Strings below could be str?
A. Give me your doughnuts.
B. What on earth is that?
C. Call me a cab, dude.
D. I found Ada’s code!

CLICKER QUESTION 3
22
Consider these statements about a String called str:
Character.isLetter(str.charAt(5)); TRUE
Character.toUpperCase(str.charAt(10)); A
Character.isWhitespace(str.charAt(13)); TRUE
Which one of the following Strings below could be str?
D. I found Ada’s code!

WORKING WITH STRINGS
PROBLEM: How to join 2 Strings (st1 and st2)
SOLUTION: Use the + operator or use st1.concat(st2)to return a new
string that appends st2 to st1.
23

INDEXOF METHOD
24
Where in the string to start looking.
Also has
lastIndexOf(item)
true

SUBSTRING OPERATIONS
T-P-S
What does fruit.substring(4, 6) return ?
25
substring(startI
ndex, endIndex)
returns substring
starting at
startIndex and
ending at
endIndex - 1.
Length of the substring
is given by endIndex
- startIndex.

CLICKER QUESTION 4
String str = “I ordered the large coffee, not the
small tea.”;
String subStr = str.substring(10, str.length());
What is the value of subStr?
A. the large coffee, not the small tea
B. the large coffee, not the small tea.
C. Error, index out of bounds.
D. he large coffee, not the small tea. 26

CLICKER QUESTION 4-ANSWER
27
String str = “I ordered the large coffee, not the
small tea.”;
String subStr = str.substring(10, str.length());
What is the value of subStr?
A. the large coffee, not the small tea
B. the large coffee, not the small tea.
C. Error, index out of bounds.
D. he large coffee, not the small tea.

COMPARING STRINGS
28
Return value from compareTo is difference between first characters in the strings that differ.
If the strings are equal, their difference is zero.
If the first string (the one on which the method is invoked) comes first in the alphabet, the
difference is negative.
Otherwise, the difference is positive.

CLICKER QUESTION 5
A. All negative values
B. All positive values
C. Negative, negative, positive, zero
D. Positive, negative, positive, zero
a compareTo(b) ->
b compareTo(c) ->
c compareTo(a) ->
c compareTo(c) ->
29

CLICKER QUESTION 5 ANSWERS
A. All negative values
B. All positive values
C. Negative, negative, positive, zero
D. Positive, negative, positive, zero
a compareTo(b) -> negative value
b compareTo(c) -> negative value
c compareTo(a) -> positive value
c compareTo(c) -> zero
30

TO-DO LIST:
• Check your iClicker grades in Moodle.
• Complete zyBook chapter 5 exercises.
• Communicate with us using only Moodle forum
or Piazza. Course staff do NOT answer emails.
• Work on Project 3.
31

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