Java basics

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Java basics

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Title: Java basics

1
Java basics

Chapter 2 (part 1 of 2)
Spring 2007
CS 101
Aaron Bloomfield

2
DisplayForecast.java

// Authors J. P. Cohoon and J. W. Davidson
// Purpose display a quotation in a console
window
public class DisplayForecast
// method main() application entry point
public static void main(String args)
System.out.print("I think there is a world
market for")
System.out.println(" maybe five
computers.")
System.out.println(" Thomas Watson, IBM,
1943.")

// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
// Authors J. P. Cohoon and J. W. Davidson //
Purpose display a quotation in a console
window public class DisplayForecast //
method main() application entry point public
static void main(String args)
System.out.print("I think there is a world market
for") System.out.println(" maybe five
computers.") System.out.println(" Thomas
Watson, IBM, 1943.")
Three comments
Three statements make up the action of method
main() Method main() is part of class
DisplayForecast
A method is a named piece of code that performs
some action or implements a behavior
An application program is required to have a
public static void method named main().
public, static, and void are keywords. They
cannot be used as names public means the method
is shareable
We will discuss static and void later
Java allows a statement to be made up of multiple
lines of text Semicolons delimit one statement
from the next
A class defines an object form. An object can
have methods and attributes Keyword class
indicates a class definition follows
A class like a method must have a name
A class like a method must have a name
Programs are read by people make sure they are
readable. Use whitespace, comments, and
indentation to aid understanding
// indicates rest of the line is a
comment Comments are used to document authors,
purpose, and program elements
3
Indentation

// Authors J. P. Cohoon and J. W. Davidson
// Purpose display a quotation in a console
window
public class DisplayForecast
// method main() application entry point
public static void main(String args)
System.out.print("I think there is a world
market for")
System.out.println(" maybe five
computers.")
System.out.println(" Thomas Watson, IBM,
1943.")

Method main() is part of DisplayForecast
Statements are part of method main()
Indentation indicates subcomponents
4
Good whitespacing

// Authors J. P. Cohoon and J. W. Davidson
// Purpose display a quotation in a console
window
public class DisplayForecast
// method main() application entry point
public static void main(String args)
System.out.print("I think there is a world
market for")
System.out.println(" maybe five
computers.")
System.out.println(" Thomas Watson, IBM,
1943.")

Whitespace
Whitespace separates program elements Whitespace
between program elements is ignored by Java
5
Bad whitespacing

The same program without any whitespacing or
comments
public class DisplayForecast2 public static
void main (String args) System.out.print("I
think there is a world market for")
System.out.println(" maybe five computers.")
System.out.println(" Thomas Watson, IBM,
1943.")

6
A whitespacing aside IOCCC

The International Obfuscated C Code Contest
Online at http//www.ioccc.org
C has very terse syntax
So the contest tries to make it terser!
One common method is by modifying the whitespace

7
A whitespacing aside IOCCC
X X
X X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X X X
XX X X XX X X
XXX X XXXXXXXXX X XXX
X X XXX X XXXX XXXX X XXX
X X XXXX X XX ainma() archa XX X XXXX
X X XXXX X oink9,igpa, X
XXXX X X XXXXXX atinlaetcharga(),iocccwa
XXXXXX X X XXXX ,apca'A',owla'a',umna2
6 XXXX X X XXX orfa(
(atinla1)(!((( XXX X X XX
atinla-apca)(apcaumna-atinla) XX X X
X gt0)((atinla-owla)(owlaumna- X X X
atinla)gt0))) utcharpa(atinla), X X
X atinlaetcharga()) orfa( atinla1 X X X
X ) orfa( igpaoink ,iocccwa( X X X
X (atinla- XXX apca)( XXX apcaumna- X X
X atinla)gt0) XXX XXX (((( X X
atinla-apca XXXXX XXXXXXX XXXXX )(apca X X
umna-atinla XXXXXX )gt0) XXXXXX ((atinla- X X
owla)(owla XXXX umna- XXXX atinla)gt0)) X
X "-Pig-" XX "Lat-in" XX "COb-fus"
X X "ca-tion!!" X (((atinla- X
apca)(apca X X umna-atinla) X gt0)?atinla-
X apcaowla X X atinla)-owla X
-'-')((igpa X oink)!(( X X igpa)'w')
X )! X (( X igpa X )owla) X X
(igpa)(( X ( XXX XXX X atinla-apca
X X )(apca X umna XXX - XXX X
atinla)gt0) X X ?atinla- X apca XXX XXX owla
X atinla), X X atinla X X X
X etcharga()) X X orfa( X
atinlaiocccwa?(( X (atinla- X X owla)(owla
X umna-atinla)gt0 X )?atinla- X X owlaapca
X atinla) X atinla ((( X X
atinla-apca) X (apcaumna- X atinla)gt0)( X X
(atinla-owla) X (owla X umna-atinla)gt X
X 0)) utcharpa( XX XX atinla),atinla X
X etcharga()) XXXXXXX orfa(igpa0, X
X igpaoink igpa utcharpa( X
X (igpa))) orfa( (atinla1)(!((( X X
atinla-apca )(apca X X
umna- XXXXX XXXXX atinla)gt0 X X
)(( XXXXX atinla- X XX
owla)( owlaumna- XX XX
atinla)gt0))) utcharpa XX XX
(atinla),atinla XX XX
etcharga()) XX XXXX
XXXX XXXXXXXXX
a(X)//X- a(X)//X- -1FX- -1FX-
-1F// -1F// charz"charz","a(
X)//X-","-1FX-","-1F//","9999999999
- ", "int q,i,j,k,X,O0,HS(x)intxXXOO
x1?x2XOx1L(n)for(", "zi1n97
ilt4i)M(256),s(i),M(128),s(i),M(64),NX8O8
s(R)charrz", "Rfor(qQr)P(r)q(Q,P
(44))M(m)P(9)i-2P(Xm?88Om?4832)P(", "9)
y(A)for(j8j)Aw--j(q0)e(W,Z)for(i-
iqilt9q)y(W(1ltlti", "Z))R()for(kJJ-4
8-40k)e(wk--,XO)main(u,v)charva(q1)b
(1)", "c(1)J--u?O?Jv153Xultlt57-vuy
(X)K40qq?e(O,X),q(K''),e(X", ",O),R(),O1
ltlt--iJJ-48(XO0)--L(q0)for(s(i0)qilt12
)s(i),igt4N", "s(q12)P(48)P('')P(59)Nq
0L(1)for(i5ilt13)s(i),NL(2)",0 b(X)/
/X- b(X)//X- -1FX- -1FX- -1F
// -1F// int q,i,j,k,X,O0,HS(x)intxX
XOOx1?x2XOx1L(n)for( zi1
n97ilt4i)M(256),s(i),M(128),s(i),M(64),NX8
O8s(R)charrz Rfor(qQr)P(r)q(Q
,P(44))M(m)P(9)i-2P(Xm?88Om?4832)P( 9)
y(A)for(j8j)Aw--j(q0)e(W,Z)for(i-i
qilt9q)y(W(1ltlti Z))R()for(kJJ-48-4
0k)e(wk--,XO)main(u,v)charva(q1)b(1)
c(1)J--u?O?Jv153Xultlt57-vuy(X)K4
0qq?e(O,X),q(K''),e(X ,O),R(),O1ltlt--iJJ
-48(XO0)--L(q0)for(s(i0)qilt12)s(i),igt
4N s(q12)P(48)P('')P(59)Nq0L(1)for(i
5ilt13)s(i),NL(2) c(X)//X- c(X)//X
- -1FX- -1FX- -1F// -1F//
define X define XX define XXX define
XXXX define XXXXX define XXXXXX define
XXXXXXX define orfa for define
XXXXXXXXX define archa char define ainma
main define etcharga getchar define utcharpa
putchar
define _ -Flt00--F-OO-- int F00,OO00main()F
_OO()printf("1.3f\n",4.-F/OO/OO)F_OO()
_-_-_-_ _-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-
_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-
_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-
_-_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-
_-_-_-_ _-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_-_-_
_-_-_-_-_-_-_-_-_-_-_-_ _-_-_-_-_-_-_-_
_-_-_-_
include ltstdio.hgt define Q rRp-'0'while(
define B breakcase chars"Qjou!s\\311-g\\311
-n\\311-c\\-q-mamO1JBHmBQ-aP1JO1HBQltnbj\
o)gps)ltlttxjudi)maQdbtf!sfuvsoltaQefgbvmu
aQltm,,aCQltcsfblabQltaN2!Q\ \ndbtf!aP2QmgtaP2Qlta!
D12J!JGJHJOJQJFJSJJJMHSHD12D12N3!N4\nJUJTUQmgtaP4
HCT\ Qs\\q,,gtm,2ltmgtaP4HCSD12N1\nJNQmgts\\..qaHC
NHbGN1!D32P3RN1UP1D12JPQUaP1H\ RPN4\nQltg\\(aP3
Q(gtaP2Q,2ltn\\(aP3Q(gtaP4HbOD12D12N2!N3\nJVP3Q,,lt
jg)aP3Qgtn\ \\(aP3Q(mgtg\\(aP3Q(ltfmtf!m,,aHCQN1
!N1\nJQqsjoug)eo-aP1QaHbQqvut)\ aP1QaHbF
N1\nQmgtaHCVP3Qgtbupj)hfut)caHbJD12JON1!Qjg)
aLN1UP1D12JIQUa\ P1HLIQmgtaN2!N2\nP2Qltfmtf!m,,aH
CMN1!N2gtP2QgtaN2\nP2Hbdd!b/d"kchar
R499 main(c,v)charvcharp,r,qfor(qs
qq)qgt' '(q)--FILEifopen(v 1,"r"),of
open(q-3,"w")for(psp)switch(p)B'M'Q(kf
getc(i))!EOF k!p)rkif(kEOF)fputs("\
n",o)fclose(o)return system(q-6)r0 B'P'whil
e(p!'')fputc(p,o)B'O'Qr)fputc(r,o)p--B
'C'k0Q kltp-'0' )(rfgetc(i),k)r0
B'I'k pif(Rk)goto G B'G'k
pGpswhile( p!''p1!
k)ppB'N'Rp-'0'0
8
Identifiers

Identifiers are names for variables, classes,
etc.
Good ones are compact, but inidicate what they
stand for
radius, width, height, length

Bad ones are either too long
theRadiusOfTheCircle
theWidthOfTheBoxThatIsBeingUsed
the_width_of_the_box_that_is_being_used

Or too short
a, b, c, d, e

Good identifiers will help the graders understand
your program!

9
Keywords

Some words are reserved, and cant be used as
identifiers

Case matters!
public ? Public ? PUBLIC
This is different than FORTRAN and BASIC
This is the same as C/C
You can use Public as a identifier
Not recommended, though!

11
Statements

A statement in Java is (usually) a single line
Example System.out.println (Hello world!)
All statements must end with a semi-colon
That tells Java that the statement is finished

12
A bit of humor1989 ComputerAdvertisement
Guess the price!
13
Variables
14
Defining variables

Weve seen variables before in math
y mx b
Here y, m, x, and b can hold any value
To store things in a computer program, we also
use variables
Example
int x 5
Visualization
This defines an integer variable with value 5
The variable is x
The type is int

15
More on variables

An integer variable can only hold integers
In other words, it cant hold 4.3
To hold floating point values, we use the double
type
double d 4.3
The variable is d
The type is double

16
Primitive variable assignment

Assignment operator
Allows the memory location for a variable to be
updated
Consider
int j 11
j 1985

Assignment operator
Allows the variable to be updated
Consider
int j 11
j 1985

17
Primitive variable assignment

Consider
int a 1
int aSquared a a
a 5
aSquared a a
Consider
int i 0
i i 1
Consider
int asaRating
asaRating 400

int a 1
int aSquared a a
a 5
aSquared a a
int i 0
i i 1
int asaRating
asaRating 400

18
Primitive variable assignment

Consider
double x 5.12
double y 19.28
double rememberX x
x y
y rememberX

Consider
double x 5.12
double y 19.28
double rememberX x
x y
y rememberX

Consider
double x 5.12
double y 19.28
double rememberX x
x y
y rememberX

Consider
double x 5.12
double y 19.28
double rememberX x
x y
y rememberX

Consider
double x 5.12
double y 19.28
double rememberX x
x y
y rememberX

Consider
double x 5.12
double y 19.28
double rememberX x
x y
y rememberX

19
Printing variables

To print a variable to the screen, put it in a
System.out.println() statement
int x 5
System.out.println (The value of x is x)
Important points
Strings are enclosed in double quotes
If there are multiple parts to be printed, they
are separated by a plus sign

public class SolvingABC
public static void main(String args)
// variable definitions and initializations
int a 3
int b 12
int c 6
int d 1
// calculate results
double result1 d a
double result2 c 2 a
double result3 d - b / c
double result4 c b c
double result5 b / 2
// display the results
System.out.println()

From this weeks lab
Note that I dont show a lot of comments so that
the code will fit on a single slide Also note
all the semi-colons
21
Variable initialization

Note that the following
int x
x 5
is (mostly) the same as the following
int x 5

22
You can only declare variables once

The following code will not work
int x 5
int x 6
Java can have only one variable named x
So you cant declare multiple variables with the
same name
(well see ways around this later in the semester)

23
Todays demotivators
24
End of lecture on 22 January 2007
25
Types
26
Primitive variable types

Java has 8 (or so) primitive types
float
double
boolean
char
byte
short
int
long

real numbers
two values true and false
a single character
integer numbers

Also the void type, which we will see later
Well only be using half of the types in this
course int, double, boolean, and char

27
Primitive real (floating-point) types

A float takes up 4 bytes of space
Has 6 decimal places of accuracy 3.14159
A double takes up 8 bytes of space
Has 15 decimal places of accuracy
3.14159265358979
Always use doubles
It will save you quite a headache!

28
Primitive integer types

Consider a byte

1 byte 8 bits
Each bit has two possibilities 0 or 1

28 256
Thus, a byte can have any one of 256 values

A Java byte can have values from -128 to 127
From -27 to 27-1

C/C has unsigned versions Java does not

29
Primitive integer types
30
Increment and decrement operators

Increments a number variable by 1
--
Decrements a numeric variable by 1
Consider
int i 4 // define
i
System.out.println(i)
System.out.print(i)
System.out.println(i)
System.out.println(i)

Increments a number variable by 1
--
Decrements a numeric variable by 1
Consider
int i 4
i // increment
System.out.println(i)
System.out.print(i)
System.out.println(i)
System.out.println(i)

Increments a number variable by 1
--
Decrements a numeric variable by 1
Consider
int i 4
i
System.out.println(i) // display
System.out.print(i)
System.out.println(i)
System.out.println(i)

Increments a number variable by 1
--
Decrements a numeric variable by 1
Consider
int i 4
i
System.out.println(i)
System.out.print(i) // update then display
System.out.println(i)
System.out.println(i)

Increments a number variable by 1
--
Decrements a numeric variable by 1
Consider
int i 4
i
System.out.println(i)
System.out.print(i)
System.out.println(i) // display then update
System.out.println(i)

Increments a number variable by 1
--
Decrements a numeric variable by 1
Consider
int i 4
i
System.out.println(i)
System.out.print(i)
System.out.println(i)
System.out.println(i) // display

Increments a number variable by 1
--
Decrements a numeric variable by 1
Consider
int i 4
i
System.out.println(i)
System.out.print(i)
System.out.println(i)
System.out.println(i)

31
Why C was named C

The increment operator adds one to the integer
value
Or makes it one better
So when Bjarne Stroustrup was making the
successor to C, he was making a one better
language

32
Primitive character type

All characters have a integer equivalent
0 48
1 49
A 65
a 97
Thus, you can refer to B as A1

33
Primitive boolean type

The boolean type has only two values
true
false
There are boolean-specific operators
is and
is or
! is not
etc.
Well see those operators in a few slides

34
Carved egg shells (done via laser)
35
Variables must be declared before use

The following code will not work
x 5
System.out.println (x)
Java requires you to declare x before you use it

36
Variable initialization

Consider the following code
int x
System.out.println(x)
What happens?
Error message
variable x might not have been initialized
Java also requires you to give x a value before
you use it

37
Constants

Consider the following
final int x 5
The value of x can NEVER be changed!
The value assigned to it is final
This is how Java defines constants
Constants have a specific naming scheme
MILES_PER_KILOMETER
All caps, with underscores for spaces

38
Expressions

What is the value used to initialize expression
int expression 4 2 5
What value is displayed
System.out.println(5 / 2.0)
Java rules in a nutshell
Each operator has a precedence level and an
associativity
Operators with higher precedence are done first
and / have higher precedence than and -
Associativity indicates how to handle ties
When floating-point is used the result is
floating point

39
Question on expressions

Does the following statement compute the average
of double variables a, b, and c? Why or why not?
double average a b c / 3.0

40
Java operators

The following are the common operators for ints
- /
Division is integer division
6 / 2 yields 3
7 / 2 yields 3, not 3.5
Because everything is an int, the answer is an
int
Modulus is
Returns the remainder
7 2 yields 1
6 2 yields 0
Floats and doubles use the same first four
operators
- /
7.0 / 2.0 yields 3.5
7.0 / 2 yields 3.5
7 / 2.0 yields 3.5
7 / 2 yields 3

41
Java operators

Booleans have their own operators
is AND
Only true when both operands are true
true true yields true
false true yields false
is OR
True when either of the operands (or both) are
true
true false yields true
false false yields false
! is NOT
Changes the value
!true yields false
!false yields true

42
New York Drivers
43
System.out.println

Can print multiple things by using the operator
Let int i 7
Example System.out.println (i i)
Prints i 7
Can also have the statement on multiple lines
System.out.println (
hello world!
)
But cant have the String on multiple lines
System.out.println (
hello
world!
)

44
System.out.println

System.out.println (result 3/5)
What does it print?
result 0
System.out.println (result 5 3)
What does it print?
result 2
System.out.println (result 3/5.0)
What does it print?
result 0.6
System.out.println (result 34.0)
What does it print?
result 34.0
System.out.println (result (34.0))
What does it print?
result 7.0

45
End of lecture on 24 January 2007
46
Methods
47
Functions

In Java, functions are called methods
Think of mathematical functions
sin()
cos()
tan()
They take input (the angle)
And produce output (the result)
In Java, they are called Math.sin(), Math.cos(),
etc.
Meaning, from the Math library, call the sin()
method

import java.util.
public class MathFun
public static void main(String args)
// set up the Scanner object
Scanner stdin new Scanner(System.in)
// have the user input the values for x and y
System.out.print("Enter a decimal number ")
double x stdin.nextDouble()
System.out.print("Enter another decimal number
")
double y stdin.nextDouble()
double squareRootX Math.sqrt(x)
System.out.println ("Square root of " x "
is "
squareRootX)

From this weeks lab
49
Scanner usage
50
Interactive programs

Programs that interact with their users through
statements performing input and output
Temperature conversion (coming up shortly)
Not interactive Celsius temperature is fixed
BMI.java (coming up somewhat less shortly)
Not interactive weight and height are fixed

51
Reading in a value from the keyboard

We will see this in more detail later in this
slide set
For now (and for lab 2), this is what you need to
know
To read in values from the keyboard, you first
have to create a Scanner object
Dont worry about what an object is, what a
Scanner is, or about creation of these things
Well get to them later
To do this, use the following code
Scanner stdin new Scanner (System.in)
NOT the following code
Scanner stdin Scanner.create (System.in)

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Reading in more values from the keyboard

You should have this only once in your program.
From then on, when you want to read in a value
into a variable, use the following
int x stdin.nextInt()
double d stdin.nextDouble()
Or
x stdin.nextInt()
d stdin.nextDouble()

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Scanner usage example

import java.util.
public class ScannerUsage
public static void main (String args)
Scanner stdin new Scanner (System.in)
System.out.println ("Enter first value")
int x stdin.nextInt()
int y
System.out.println ("Enter second value")
y stdin.nextInt()
int z x y
System.out.println ("The sum of " x " and "
y " is " z)

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Program demo

ScannerUsage.java
Note that all this code is available on the
website!

55
How to make Java work with the Scanner class

In Java 1.5, do aimport java.util.
To create a new ScannerScanner stdin new
Scanner (System.in)

56
Todays demotivators
57
Program Examples
58
Example program temperature conversion
// Purpose Convert a Celsius temperature to
Fahrenheit public class CelsiusToFahrenheit
// main() application entry point public
static void main(String args) // set
Celsius temperature of interest int celsius
28 // convert to Fahrenheit
equivalent int fahrenheit 32 ((9
celsius) / 5) // display result
System.out.println("Celsius temperature")
System.out.println(" " celsius)
System.out.println("equals Fahrenheit
temperature") System.out.println(" "
fahrenheit)
59
Program demo

CelsiusToFahrenheit.java

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Computation

Programmers frequently write small programs for
computing useful things
Example body mass index (BMI)
Measure of fitness
Ratio of persons weight to the square of the
persons height
Weight in is kilograms, height is in meters
Person of interest is 4.5 feet and weighs 75.5
pounds
Metric conversions
Kilograms per pound 0.454
Meters per foot 0.3046

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Program outline for BMI.java

// Purpose Compute BMI for given weight and
height
public class BMI
// main() application entry point
public static void main(String args)
// define constants
// set up person's characteristics
// convert to metric equivalents
// perform bmi calculation
// display result

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BMI.java define constants
// define constants final double
KILOGRAMS_PER_POUND 0.454 final double
METERS_PER_FOOT 0.3046
// define constants final double
KILOGRAMS_PER_POUND 0.454 final double
METERS_PER_FOOT 0.3046
// define constants final double
KILOGRAMS_PER_POUND 0.454 final double
METERS_PER_FOOT 0.3046
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BMI.java personal characteristics

// set up person's characteristics
double weightInPounds 75.5 // our persons
weight
double heightInFeet 4.5 // our persons
height

// set up person's characteristics
double weightInPounds 75.5 // our persons
weight
double heightInFeet 4.5 // our persons
height

// set up person's characteristics
double weightInPounds 75.5 // our persons
weight
double heightInFeet 4.5 // our persons
height

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BMI.java convert to metric equivalents
// convert to metric equivalents
double metricWeight weightInPounds
KILOGRAMS_PER_POUND double metricHeight
heightInFeet METERS_PER_FOOT
// convert to metric equivalents
double metricWeight weightInPounds
KILOGRAMS_PER_POUND double metricHeight
heightInFeet METERS_PER_FOOT
// convert to metric equivalents
double metricWeight weightInPounds
KILOGRAMS_PER_POUND double metricHeight
heightInFeet METERS_PER_FOOT
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BMI.java perform BMI calculation

// perform bmi calculation
double bmi metricWeight / (metricHeight
metricHeight)

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BMI.java display result
// display result System.out.println(
"A person with") System.out.println("
weight " weightInPounds " lbs")
System.out.println(" height " heightInFeet "
feet") System.out.println("has a BMI of "
Math.round(bmi))