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ch02-primitive-data-definite-loops.pdf
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详细说明：java 基础入门学习1-18章节，连续上传。希望对大家有帮助Java' s primitive types
primitive types: 8 simple types for numbers text, etc
Java also has object types, which well talk about later
Name
Description
Examples
nt
ntegers
(upto231-1)
42,-3,0,926394
double
real numbers (up to 10308
3.1,-0.25,9,4e3
char
single text characters
n
boolean logical values
true,fa⊥se
Why does Java distinguish integers vs real numbers?
Expressions
expression: a value or operation that computes a value
o Examples:
(7+2)6/3
42
The simplest expression is a literal value
A complex expression can use operators and parentheses
Arithmetic operators
operator: combines multiple values or expressions.
addition
subtraction(or negation)
multiplication
/。
division
modulus(ak a remainder)
As a program runs, its expressions are evaluated
1 +1 evaluates to 2
System. out. println(3 4)i prints 12
How would we print the text 3 4?
Integer division with/
When we divide integers the quotient is also an integer
14/4is3,not3.5
3
52
4)14
10
45
27)1425
12
40
135
5
75
54
21
● More examples
32/5
Is 6
84/10is8
156/100is1
Dividing by 0 causes an error when your program runs
Integer remainder with o
The o operator computes the remainder from integer division
14
Is 2
218%5is3
What is the result?
45
43
4)14
5)218
282
12
20
8820
2
11
15
Applications of o operator
Obtain last digit of a number 230857 10 is 7
Obtain last 4 digits
658236489810000s6489
See whether a number is odd
2|s1,422s0
Precedence
precedence: Order in which operators are evaluated
Generally operators evaluate left-to-right
1-2-3is(1-2)-3 which is-4
But大/各 have a higher level of precedence than+
1+3★4
s13
6+8/2
6
6+
12
S 1
Parentheses can force a certain order of evaluation
(1+3)大4
Is 1
Spacing does not affect order of evaluation
1+34-2
s11
Precedence examples
1大2+35
1+832
+3大5
1+2
大2
2
+15
1+
2
3
Precedence questions
What values result from the following expressions?
9/5
69520
7+65
7大6+5
248100/5
大
(5-7)大4
(18(17-12))
10
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