information technology studies computer programming 1

Department of Information TechnologyStudies

Computer Programming 1


Decision MakingModule 4


if and if..else Structure

• Learn about decision making

• Make decisions with the if and if...elsestructures

• Use multiple statements in an if or if...else structure

• Nest if and if...else statements

• Use AND and OR operators

4NLAC Department of

Information Techonology Studies

Objectives

October 13, 2021

• Learn to make accurate and efficient decisions

• Use the switch statement

• Use the conditional and NOT operators

• Understand precedence

5NLAC Department of


Objectives (continued)

October 13, 2021

• Pseudocode– Use paper and pencil

– Plan program’s logic • By writing plain English statements

– Accomplish important steps in a given task

– Use everyday language

• Flowchart– Steps in diagram form

– Series of shapes connected by arrows

6NLAC Department of

Information TechonologyStudies

Understanding Decision Making

October 13, 2021

• Flowchart (continued)

– Programmers use variety of shapes to represent different tasks

• Rectangle to represent any unconditional step

• Diamond to represent any decision

• Sequence structure

– One step follows another unconditionally

– Cannot branch away or skip a step

7NLAC Department of


Understanding Decision Making (continued)

October 13, 2021

• Decision structure

– Involves choosing between alternative courses of action

– Based on some value within program

• All computer decisions are yes-or-no decisions

• Boolean values

– Values true and false

– Used in every computer decision

8NLAC Department of


Understanding Decision Making (continued)

October 13, 2021

• if statement

– Simplest statement to make decision

– Boolean expression appears within parentheses

– Space between keyword if and opening parentheses

– Execution always continues to next independent statement

– Use double equal sign (==) to determine equivalency

9NLAC Department of


Making Decisions with theif and if...else Structures

October 13, 2021

if Structure

if (booleanExpression)

single statement;

if Statement

Evaluates to true or false

Must be enclosed in

parentheses.

Remember to indent the subordinate statement

October 13, 2021NLAC Department of Information

Techonology Studies11

Syntax:

if flowchart

Boolean

test

Subordinate

statement(s)

Independent

statement(s)

true

false



Example:



if (x == 0)

System.out.println(“The number is zero”);

System.out.println(“Program Terminated”);

Example:int m = 5;

if (m >= 0)

System.out.println(m);

System.out.println(m+1);

Statement

executes

The booleantest returns

TRUE,

Exits

outside the

if and

execute the

independent

statement

5m

Output:



Example:int m = 5;

if (m >= 10)



Ignores if statement

The booleantest returns

FALSE,

Exits

outside the

if and

execute the

independent

statement

5m

Output:



start

i >= 5

i = 5

Print (i+1)

end

yes

no

Fig. 1 Program Flowchart October 13, 2021

NLAC Department of Information Techonology Studies

16

print i

Pitfall: Misplacing a Semicolon in an if Statement

• No semicolon at end of first line of if statement

– if (m == 10)

– Statement does not end there

• When semicolon follows if directly

– Empty statement contains only semicolon

– Execution continues with the next independent statement NLAC Department of Information


int m = 5;

if (m >= 0)



October 13, 2021

Pitfall: Misplacing a Semicolon in an if Statement

• No semicolon at end of first line of if statement

– if (m == 10)

– Statement does not end there

• When semicolon follows if directly

– Empty statement

– Execution continues with the next independent statement

NLAC Department of Information


int m = 5;

if (m >= 0);



Do not do this

Indention has no effect

October 13, 2021

• Attempt to determine equivalency– Using single equal sign

– Rather than double equal sign

– Illegal

• Can store Boolean expression’s value in Boolean variable– Before using in if

statement

19

NLAC Department of

Information Techonology

Studies

Pitfall: Using the Assignment Operator Instead of the Equivalency Operator

int m = 5;

if (m = 0)



Use equivalency symbol ==

October 13, 2021

• Problem#1: Create a java program that allows the user to enter a name, the birth year and the current year. Compute and display the age. If the age is lower than 18, display the message, “Your are not yet allowed to vote!”; otherwise, the program terminates.

• Formula:

age = current year - birth year



• Pseudocode:

1. enter the name, the birth year and current year

2. Compute the age.

3. If age is lower than 18

• Display message, “Your are not allowed to vote!”

4. Otherwise,

• Program terminatesOctober 13, 2021


22

start

Name,Birth year,

Current year

age < 18

age = current year – birth year

You are not allowed to vote

end

yes

noFig. 1 Program Flowchart



Activity

• Problem#2: Create a java program that allows the user to enter the customer a name, the bill amount of the customer . A 5% discount rate is given to the customer if the amount bill is 1000 and above; otherwise, the program terminates. Compute and display the discount and the amount due of the customer.

• Formula:

Discount = bill amount * 0.05

amount due = bill amount – discount





ifP2Ans.pptx

More Activities on if structure

• Write a java program that allows the user to enter the customer name, age, and bill.

• If the age is 60 and above, a 20% discount is deducted from the bill of the senior citizen.



if..else Structure

The if...else Statement


{

statement(s);

}

else

{

statement(s);

}

Note: blocks with braces are

necessary when there are

multiple subordinate

statements. They are optional

when there is a single

subordinate statement.



Syntax:

if-- else flowchart

Boolean

test

statement(s)

subordinate to if

Independent

statement(s)

true

false

statement(s)

subordinate to else



• if...else

statement

– Performs one action when Boolean expression evaluates true

– Performs different action when Boolean expression evaluates false

31NLAC Department of


if...else Structure (cont)

if

(booleanExpression)

{

statement(s);

}

else

{

statement(s);

}

October 13, 2021

• if...else

statement (continued)

– Statement that executes when if is true or falseends with semicolon

– Vertically align keyword if with the keyword else



The if...else Structure (continued)


{

statement(s);

}

else

{

statement(s);

}

October 13, 2021

• if...else

statement (continued)– Illegal to code else without if

– Depending on evaluation of Boolean expression following if• Only one resulting

action takes place



The if...else Structure (continued)

if (booleanExpression);

{

statement(s);

}

else

{

statement(s);

}

October 13, 2021

• Execute more than one statement

– Use pair of curly braces

• Place dependent statements within block

• Crucial to place curly braces correctly

34

NLAC Department of


Studies

Using Multiple Statementsin an if or if...else Structure

October 13, 2021


{

statement(s);

}

else

{

statement(s);

}

• Any variable declared within block local to that block

35

NLAC Department of


Studies

Using Multiple Statementsin an if or if...else Structure

October 13, 2021


{

int var1;

...;

}

else

{

statement(s);

}

• Problem#1: Create a java program that allows the user to enter the customer a name, the bill amount of the customer and customer status code( 1- regular customer, and 2- walk in customer). Only regular customer receives a discount of 10%. Compute and display the discount and the amount due of the customer.

• Formula: amount due = bill amount - discount



• Pseudocode:

1. enter the customer name, the bill amount of the customer and customer status code

2. If the customer status code is 1

a. Compute for the discount

3. Otherwise,

a. No discount

4. Compute the amount due.

5. Display the discount, and the amount due.



start

Customer nameBill amount

Customer status code

Status code is 1?

Discount = 0

Discount = bill amount * .10Discount

Amount due

Amount due = bill amount - discount

end

yes

no



39

Variable declaration & intitialization

Accepts input from the user

If boolean test returns TRUE, execute

Goes out from the if, then execute independent statement

If booleantest returns FALSE, execute

Group Activity

• Problem#1: Create a java program that allows the user to enter the student name, and the average grade. Determine whether the grade is PASSED or FAILED.

• Write the pseudocode and draw the flowchart of the given problem.



Group Activity • Problem#2: Create a program that will allow the user to enter the

employee name, rate per hour and hours worked. Compute for the overtime hours and overtime pay, and the regular pay if hours worked is more than 40 hours; otherwise computer for the regular pay, overtime hours and overtime pay is zero. Compute and display the regular pay, tithe, gross pay, and net pay.

• Formula:

• OT Hours = hrs worked – 40

• OT Pay = OT hours * rate per hour * 1.5

• Regular pay = rate per hour * 40 (for hours worked more than 40)

• Tithe = 10 % of regular pay

• Gross pay = sum ot regular pay & OT Pay

• Net pay = gross pay less titheOctober 13, 2021


42



ifElseP2Ans.pptx

Group Activity

• Problem#3: Create a java program that allows the user to enter the student name, and the gender code M or F. Display Male for M and Female for F.

• Write the psuedocode and draw the flowchart



start

Student name,Gender code

Gender code ==

‘M’

Male

end

yes



45

Female

no

Code Segment:

char genderCode;

String studName;

System.out.println(“Student name: ”);

studName = input.nextLine();

System.out.println(“Gender Code [M/F]: ”);

genderCode = input.next().charAt(0);

if (genderCode == ‘M’)

System.out.println(“Male”);

else

System.out.println(“Female”);



Code Segment:

char genderCode;

String studName;







else




The if-else if Statement

The if-else if Statement

Sometimes you need to be able to test a series of conditions

You can do this with the if-else if statement



If BooleanExpression1is true, then statement or block 1 is executed.

If BooleanExpression1is false, then BooleanExpression2

is tested. If BooleanExpression2 is

true, then statement orblock 2 is executed.

If BooleanExpression2 is false, then statement orblock 3 is executed.



if (booleanExpression1)

{

statement/block1;

}

else if (booleanExpression2)

{

statement/block2;

}

...

else

{

statement/block3;;

}

Syntax:

Note: You can have as many if else clauses as is needed.

FlowChart for if – else if (cont)

Boolean

test

statement(s)

subordinate to if

Independent

statement(s)

true

false

statement(s)

subordinate to elseif

Boolean

test

false

statement(s)

subordinate to else

true



start

Student name,Gender code

Gender code ==

‘M’

Male

end

yes

no



53

Gender code == ‘F’

Female

yes

no

Code Segment:

char genderCode;

String studName;







else




Code Segment:

char genderCode;

String studName;







else if (genderCode == ‘F’)




• Logical AND operator

– Alternative to some nested if statements

– Used between two Boolean expressions to determine whether both are true

– Written as two ampersands (&&)

• Include complete Boolean expression on each side

– Both Boolean expressions that surround operator

• Must be true before action in statement can occur



Using Logical AND and OR Operators

October 13, 2021

Example: Using the && Operator

if ( num > 0 && num < 10 )

System.out.println( "num is between 0 and 10" ) ;



Using Logical Operators

October 13, 2021

System.out.print("Student name: ");


System.out.print("Gender Code [M/F]: ");


if (genderCode == 'M' || genderCode=='m')

System.out.println("Male");

else if (genderCode == 'F' || genderCode=='f')

System.out.println("Female");



• Nested if statements

– Statements in which if structure is contained inside of another if structure

– Use when two conditions must be met before some action is taken

• Pay careful attention to placement of elseclauses

• else statements

– Always associated with if on “first in-last out” basis



Nesting if and if...elseStatements

October 13, 2021

Syntax:if(Boolean_expression 1)

{

if(Boolean_expression 2)

{

statement(s);

}

}

Example:if ( num > 0 ) // Outer if

if ( num < 10 ) // Inner if

System.out.println( "num is between 0 and 10" ) ;



Nesting if and if...elseStatements

Statement of inner if

Statement of outer if

October 13, 2021

Laboratory Activity



Up Next: switch…case Statement

labIFs.pptx

• switch statement

– Alternative to series of nested if statements

– Test single variable against series of exact integer or character values

63

NLAC Department of


Studies

Using the switch Statement

October 13, 2021

• Switch structure keywords

– switch

• Starts structure

• Followed by test expression

• Enclosed in parentheses

– case

• Followed by one of the possible values for test expression and colon



Using the switch Statement (continued)

October 13, 2021

• Switch structure keywords (continued)– break

• Optionally terminates switch structure at end of each case

– default

• Used prior to any action if test variable does not match any case

• Optional




October 13, 2021


66

Example using the switch Statement

int year;

System.out.println(“Enter year: “);year = input.nextInt();

if (year==1)System.out.println(“Freshman”);

else if (year==2)System.out.println(“Sophomore”);

else if (year==3)System.out.println(“Junior”);

else if (year==4)System.out.println(“Senior”);

else System.out.println(“Invalid Year”);

October 13, 2021

• break statements in switch structure

– If break statement omitted

• Program finds match for test variable

• All statements within switch statement execute from that point forward

• case statement

– No need to write code for each case

– Evaluate char variables

• Ignore whether uppercase or lowercase




October 13, 2021

• Why use switch statements?

– Convenient when several alternative courses of action depend on single integer or character variable

– Use only when there are reasonable number of specific matching values to be tested




October 13, 2021

Exerciseif (a==1)

x += 6;

else if (a == 2)

x += 10;

else if (a == 3)

x += 16;

else if (a == 4)

x += 34;

Convert this if statement into a switch statement



• NOT operator– Written as exclamation point (!)

– Negates result of any Boolean expression

– When preceded by NOT operator • Any expression evaluates as:

– true becomes false

– false becomes true

• Statements with NOT operator– Harder to read

– Require double set of parentheses



Using the NOT Operator

October 13, 2021

• Combine as many AND or OR operators as needed

• Operator’s precedence

– How expression is evaluated

– Order agrees with common algebraic usage

• Arithmetic done first

• Assignment done last

• AND operator evaluated before OR operator

• Statements in parentheses evaluated first



Understanding Precedence

October 13, 2021


72

Understanding Precedence (continued)

October 13, 2021

• Two important conventions

– Order in which operators are used

– Always use parentheses

• Change precedence

• Or make your intentions clearer



Understanding Precedence (continued)

October 13, 2021

information technology studies computer programming 1

Documents