BUILDING JAVA PROGRAMS CHAPTER 2 PRIMITIVE DATA TYPES AND OPERATIONS

22 OBJECTIVES Identify Java’s primitive data types and operators. Evaluate complex expressions using rules of precedence and mixed types.

33 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 = “hello” =

44 JAVA’S PRIMITIVE DATA TYPES NameDescriptionExample int integers (whole numbers) 42, -3, 18, 20493, 0 double real numbers 7.35, , 18.0 char single characters 'a', 'X', '3', '\n' boolean logical values true, false Variations of int: byte, short, long Variations of double: float

55 JAVA’S ARITHMETIC OPERATORS OperatorMeaningExampleResult + addition – subtraction 53 – 1835 * multiplication 3 * 824 / division 4.8 / % mod (remainder) 19 % 54 Most behave exactly like you would expect them to in math class, but we’ll learn about the exceptions soon.

66 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 * * (1.3 – (5.7 – 3)) System.out.println( 5 * 2 / );

77 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 = / 3.0 = (rounding error!) 4.0 / 5.0 = / 3.0 * 3.0 = 8.0

88 INTEGER DIVISION… WEIRD… When dividing integers, we keep the whole part, but discard the fractional part. 5 / 2 = 2 not / 3 = 3 not 3.333… 4 / 5 = 0 not / 3 * 3 = ?2 * 3 =? 6 not 8!

99 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 = % 2 =13856 % 2 = 8374 % 10 =8374 % 100 = 36 % 6 =7 % 9 =

10 In your notebook… 1. Write four expressions using only % and / that will get me the four individual digits of a b c d *** Will your expressions work for other four-digit numbers? *** / 1000 % 10 / 100 % 10 / 10 % 10 THINK, PAIR, SHARE… = 2 = 8 = 3 = 7 ????? % 10 ?????

11 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: DescriptionOperators unary operators +, - multiplicative operators *, /, % additive operators +, -

12 PRECEDENCE EXAMPLES * 5 = 12not 20 3 * * 2 = 13not / 2 * 3 – 4 = 9not * -4 = = = 7

13 MIXING TYPES When doing an operation on an int and a double, the int gets promoted to a double. 1 * = / 2.0 = * 1.0 / 2 = / 2 – 7 / 2 = ? 3.5 – 3 =? 0.5

14 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

15 IN YOUR NOTEBOOK… 4.0 / 2 * 9 / * 9 / / 2 9.0

16 IN YOUR NOTEBOOK… 12 / 7 * 4.4 * 2 / 4 1 * 4.4 * 2 / * 2 / / 4 2.2

17 IN YOUR NOTEBOOK… 9 / / 3 – 3.0 / / 3 – 3.0 / – 3.0 / – –

18 IN YOUR NOTEBOOK… 53 / 5 / ( ) / / 2 53 / 5 / 2.0 / / 2 10 / 2.0 / / / / /