building java programs chapter 2

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BUILDING JAVA PROGRAMS CHAPTER 2 PRIMITIVE DATA TYPES AND OPERATIONS

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Building Java Programs Chapter 2. PRIMITIVE DATA TYPES AND OPERATIONS. Objectives. Identify Java’s primitive data types and operators . Evaluate complex expressions using rules of precedence and mixed types. Data Types. A name for a category of data values that are all related. - PowerPoint PPT Presentation

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Page 1: Building Java  Programs Chapter 2

BUILDING JAVA PROGRAMSCHAPTER 2PRIMITIVE DATA TYPES AND OPERATIONS

Page 2: Building Java  Programs Chapter 2

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OBJECTIVES

Identify Java’s primitive data types and operators.

Evaluate complex expressions using rules of precedence and mixed types.

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DATA TYPES

A name for a category of data values that are all related.

Different data types support different operations and behave differently.You can multiply numbers, but can you multiply strings? Can you add them?

Stored differently in computer memory as well.27 = 00011011

“hello” = 01101000 00000101 1101100 1101100 01101111

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JAVA’S PRIMITIVE DATA TYPES

Name Description Example

int integers (whole numbers)

42, -3, 18, 20493, 0

double real numbers 7.35, -19.83423, 18.0

char single characters 'a', 'X', '3', '\n'

boolean logical values true, false

Variations of int: byte, short, long

Variations of double: float

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JAVA’S ARITHMETIC OPERATORS

Operator Meaning Example Result

+ addition 2 + 2 4

– subtraction 53 – 18 35

* multiplication 3 * 8 24

/ division 4.8 / 2.0 2.4

% mod (remainder)

19 % 5 4

Most behave exactly like you would expect them to in math class, but we’ll learn about the exceptions soon.

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EXPRESSIONS

An expression is a simple value or a set of operations that produces a value.

Simplest expressions are literals of the data types we know. E.g. 27, “Seattle... Yay!", -1.7, false

More complex expressions can use operators and parentheses. E.g.:

5 * 2 7 - 3 * (1.3 – (5.7 – 3))

System.out.println( 5 * 2 / 3 + 6 );

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FLOATING-POINT DIVISION

When dividing double or float values, it’s just like math class, but with some rounding errors here and there…

5.0 / 2.0 = 2.5

10.0 / 3.0 = 3.3333333333333335 (rounding error!)

4.0 / 5.0 = 0.8

8.0 / 3.0 * 3.0 = 8.0

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INTEGER DIVISION… WEIRD…

When dividing integers, we keep the whole part, but discard the fractional part.

5 / 2 = 2 not 2.5

10 / 3 = 3 not 3.333…

4 / 5 = 0 not 0.8

8 / 3 * 3 =

?2 * 3 = ?6 not 8!

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INTEGER MOD (%)

The mod operator computes the remainder of a division

6 / 4 = 1, but it would have had a remainder 2

Therefore, 6 % 4 = 2

20 % 7 = 15 % 4 =

13857 % 2 = 13856 % 2 =

8374 % 10 = 8374 % 100 =

36 % 6 = 7 % 9 =

6 3

1 0

4 74

0 7

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In your notebook…

1. Write four expressions using only % and / that will get me the four individual digits of 7382.

a. 7382

b. 7382

c. 7382

d. 7382

*** Will your expressions work for other four-digit numbers? ***/ 1000 % 10

/ 100 % 10

/ 10 % 10

THINK, PAIR, SHARE…

= 2

= 8

= 3

= 7

?????

?????

?????

% 10

?????

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OPERATOR PRECEDENCE

Usually, we evaluate expressions left-to-right, but certain operations take precedence over others and get evaluated first.

Parentheses can always override precedence.

Precedence table:

Description Operators

unary operators +, -

multiplicative operators *, /, %

additive operators +, -

Page 12: Building Java  Programs Chapter 2

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PRECEDENCE EXAMPLES

2 + 2 * 5 = 12 not 20

3 * 3 + 2 * 2 = 13 not 22

7 + 5 / 2 * 3 – 4 = 9 not 14

+3 * -4 = -12

3 + -4 = -1

3 - -4 = 7

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MIXING TYPES

When doing an operation on an int and a double, the int gets promoted to a double.

1 * 4.682 = 4.682

7 / 2.0 = 3.5

5 * 1.0 / 2 = 3.0

7.0 / 2 – 7 / 2 =

?3.5 – 3 = ?0.5

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CASTING

You can explicitly convert a value from one data type to another by casting.

(double) 99 = 99.0

(int) 2.5 = 2

((double) 7) / 2 = 3.5

(int) 2.5 * 3.0 = 6.0

(int) (2.5 * 3.0) = 7

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IN YOUR NOTEBOOK…

4.0 / 2 * 9 / 2

2.0 * 9 / 2

18.0 / 2

9.0

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IN YOUR NOTEBOOK…

12 / 7 * 4.4 * 2 / 4

1 * 4.4 * 2 / 4

4.4 * 2 / 4

8.8 / 4

2.2

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IN YOUR NOTEBOOK…

9 / 2.0 + 7 / 3 – 3.0 / 2

4.5 + 7 / 3 – 3.0 / 2

4.5 + 2 – 3.0 / 2

4.5 + 2 – 1.5

6.5 – 1.5

5.0

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IN YOUR NOTEBOOK…

53 / 5 / (0.6 + 1.4) / 2 + 13 / 2

53 / 5 / 2.0 / 2 + 13 / 2

10 / 2.0 / 2 + 13 / 2

5.0 / 2 + 13 / 2

2.5 + 13 / 2

2.5 + 6

8.5