computer programming (tmk 3102) lecture notes 6

8/9/2019 COMPUTER PROGRAMMING (TMK 3102) LECTURE NOTES 6

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TMK 3102-Chap 6: Operators &

Ex ression

1

Chapt er 6: Opera t ors&Express ions

Session Plan (Week 6):To understand:

arithmetic operators and their order of

precedence


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TMK 3102-Chap 6: Operators &Ex ression

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I n t roduc t ion We use arithmetic expressions to solve most

programming problems

Arithmetic expressions comprise of operators

and operands

There are rules for writing and evaluating

arithmetic expressions


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3

Operat or and Operand

What are operator andoperand?

Example:

W + Z

Operand

Operator

Operand


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Operator & Operand

Example:

Which is which?

A / BOperator ??

Operand??


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5

Basic Ar i t hm et ic Opera t ors

Addition (+)

Subtraction (-)

Multiplication (*)

Division (/)

Modulus (%)


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Basic Ar i t hm et ic Opera t ors

Multiplication, addition and subtractionare the simplest to use

Division is easy, but some precautions needto be taken

Modulus is the one that normally confusesnovices

So, lets study in detail the Division andModulus


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Divis ion

Example:

W / Z

Floating Division

W or Z or both are

floats

Integer Division

W and Z are integers


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In t eger Div is ion

Example:

8 / 2 = 4

an integer

an integer

the result is

also an integer


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In t eger Div is ion

Example:

12 / 5 = 2

an integer

an integer

the result is

also an integer


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Float ing Div is ion

Example:

12.0 / 5 = 2.0

a float

an integer

the result is afloat


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Som et h ing to ponder

What will be the answer

if an integer is dividedby 0? How about if oneof the operands is anegative integer?


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Modulus

It returns the remainder that occursafter performing the division of 2

operands


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Modulus

Example:

12 % 5 = 2

an integer

an integer

the result is theremainder of 12/5

125

2

10

2

remainderresult


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Modulus

Example:

7 % 3 = 1

an integer

an integer

73

2

6

1

remainderresult

the result is theremainder of 7/3


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The earlier expressions

contain only oneoperator at a time. Whatif the expression

contains more than oneoperator?


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Ar it hm et ic Ex press ion

An expression may contain 2 or more

arithmetic operators

Main issue:

ORDER OF PRECEDENCE


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Examples:

5 + 6

5 + 6 * 2

2.5 + 6 2 * 2

12 / 6.0 2 * 2

= 11

= 22 or 17?

= ??

= ??

= 17


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Order of Precedence:

High: * / %

Low: + -

All operators have a precedence level. Highprecedence level operators are evaluated before

lower ones. Operators of the same precedencelevel are evaluated from left to right


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Example:2.5 + 6 2 * 2 = ??

4

8.5

2.5 + 6

4

4.5

2.5 + 6 2 * 2 =Example:

2.5 + 6 2 * 2 = 4.5

4

8.5

2.5 + 6

4

4.5

2.5 + 6 2 * 2 =


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Try i t !

Example:

12 + 6.0 2 * 2 = ??

Whats the answer??


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All expressions in parentheses (brackets)must be evaluated prior to values outsidebrackets

Nested parenthesized expressions must beevaluated from the inside out, with theinnermost expression evaluated first

Example:

( 9 ( 3 + 2 ) ) * 3 = ??


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Example:

( 9 ( 3 + 2 ) ) * 3 = ?? 54 12( 9 ( 3 + 2 ) ) * 3 = 12


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Assignm ent St a t em ent

There are 3 types of assignment:

Simple

Multiple

Shorthand


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Sim ple Ass ignm ent

Syntax:

variable = expression ;

Dont forget the semicolon !!


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Sim ple Ass ignm entImport java.utils.Scanner;

public class discount {

public static void main(String [] args ) {

Scanner in = new Scanner(System.in);

float price, discount, total;

System.out.print(Buying price : );price = in.nextDouble();

System.out.print(Discount rate : );

discount=in.nextDouble();

total = price (price * discount);

System.out.println(For buying price + price + and discountrate + discount);

System.out.println(The total price is + total);

}

}

Buying price: _

discount ??

price ??

total ??

Buying price: 10.00

_

10.00

Buying price: 10.00

Discount rate: _

Buying price: 10.00

Discount rate: 0.25

_

0.25

7.50

Buying price: 10.00

Discount rate: 0.25

For buying price RM10.00 and discount rate 0.25

_

Buying price: 10.00

Discount rate: 0.25

For buying price RM10.00 and discount rate 0.25

The total price is RM7.50

_


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Mul t ip le Ass ignm ent

Syntax:

variable = variable = expression ;

Dont forget the semicolon !!


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Example:

int number, total;

float start_x, start_y;

. . .

number = total = 0;

start_x = start_y = 100.0;

total ??

number ??

start_x ??

start_y ??

0

0

100.0

100.0

Mul t ip le Ass ignm ent


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Shor t hand Ass ignm ent

Syntax:

variableX = variableX opexpression ;

variableX op= expression;


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Whenever the expression on the right

contains the variable on the left (to which

the value is assigned)Example:

num = num + 5;

num 15

15 + 520

20


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Expressions can also be stated using

shorthand assignment operators

Example:num += 5; similar to num = num + 5

shorthand assignment operator

Shorthand assignment operators have the lowest

order of precedence the last one to be evaluated


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Operation Examples ofexpression

Description

+= num += 5; num = num + 5;

-= num -= 5; num = num 5;

*= num *= 5; num = num * 5;

/= num /= 5; num = num / 5;

%= num %= 5; num = num % 5;


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Example:

pay += hour * rate * 2

pay + (8 * 5.00 * 2)

pay 100.00

hour 8rate 5.00

similar to pay = pay + (hour * rate * 2)

pay + (hour * rate * 2)

100.00 + 80.00 180.00

180.00


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Ass ignm ent by Value

Every assignment expression has a value

Example:

Expression 1: a = 1;

Expression 2: x = y = 0;

Expression 3: p = 12;

p = 0;

Example:

int a, x, y, p;

Line 1: a=1;

Line 2: x = y = 0;

Line 3: p = 12;Line 4: p = p +3;

Line 5: q = p = p + x;


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Relat ional Operat ors

Operation Description Examplesof

Expression

Value

< Less than 6 < 9 true

6 false

>= Greater than or equal to 9 >= 5 true

== Equal to 7 == 5 false

!= Not equal to 6 != 5 true


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Mant ic /Logic a l Operat ors

Symbol Description && AND || OR

! NOT

a b a && b a || b !a !b

T T T T F F

T F F T F TF T F T T F

F F F F T T


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Com pound St at em ent

Arithmetic, relational and mantic operators can be

integrated/combined in one expression

Example:

! ( c > a )a 2

b 5

c 15

d 17 ! ( true ) ! ( 15 > 2 ) false


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Example:

(a >= 1) && (b == 5)

a 2

b 5

c 15

d 17

( 2 >= 1 ) && ( b == 5 )

true && ( b == 5 )

true && ( 5 == 5 ) true && true

true


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Example:

(c >= ( b * 3 ) ) || (a == 3)

a 2

b 5

c 15

d 17

( c >= ( 5 * 3 ) ) || ( a == 3)

true || ( a == 3 )

true || ( 2 == 3 )

true || false

( 15 >= 15 ) || ( a == 3)

true


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Example:

! ( ( a < b ) || ( c > d ) )

a 2

b 5

c 15

d 17

! ( ( 2 < 5 ) || ( c > d ) )

! ( true || ( 15 > 17 ) )

! ( true || false )

! true

! ( true || ( c > d ) )

false


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Inc rem ent and Dec rement

This operation contains only one operand, that is,the operand which value will be incremented/

decremented

Symbol Description Examplesof

Expression

Description

++ Incrementoperand by 1

i++ i = i + 1

-- Decrementoperand by 1

i-- i = i 1


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Inc rem ent and Dec rement

Key-in a number: _Key-in a number: 26

_

Example:

int num;

System.out.println(Key-in a number: );

num=in.nextInt();System.out.println(Value before being incremented: + num);

num++;

System.out.println(Value after being incremented: +num);

num ??

Key-in a number: 26

Value before being incremented: 26

_

2627

Key-in a number: 26

Value before being incremented: 26

Value after being incremented: 27 _


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Pref ix and Post f ix

Increment and Decrement operators canbe either in prefix or postfix forms

Expression Description

i++ Value of i is incremented after being used in theexpression

++i Value of i is incremented before being used inthe expression

i-- Value of i is decremented after being used inthe expression

--i Value of i is decremented before being used inthe expression


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Example:

j = i++ - 2

i 5

similar to

j = i 2;

i = i + 1; j ??3

6


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Example:

j = ++i - 2

i 5

similar to

i = i + 1;

j = i 2; j ??4

6


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The earlier expressions

contain only one type ata time. What if theexpression containsmore than one type?


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Conversion Rules

When performing a binary operation involvingtwo operands of different type, Javaautomatically converts the operand based onthe following rules

If one of the operands is double, the other isconverted into double

Otherwise, if one of the operands is float, theother is converted to float

Otherwise, if one of the operands is long, theother is converted to long Otherwise, both operands are converted to int


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Convers ion Problem s Ex am ple

byte i = 100;long k = i * 3 + 4;

double d = i * 3.1 + k / 2;


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Type Cast ing

Example:int x = (int) 3.0; // type narrowing

int y = (int) 65.76;//truncationy 65

x 3

Casting is used to compute a value that is equivalent

to its operands value (based on the stated data type)


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Type Cast ing Ex am ple

Example:

int x;

float y = 35.87;

x = (int) y;

( int ) 35.87

35

y 35.87

x ??35


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THINK!! !

What is wrong?

int i = 5;double d = 2.0;

int x = i/d;


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Thank You

computer programming (tmk 3102) lecture notes 6

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