Input and Java A Quick Intro

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Input and Java A Quick Intro

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param vintner The vintner (maker) of the wine. ... double proof, String vintner, String varietal, int vintage) ... System.out.println('Vintner : ' bottle1.getVintner ... – PowerPoint PPT presentation

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Title: Input and Java A Quick Intro

1
Input and Java A Quick Intro

In Java, we can do Input as well. Rather than go
into details right now Ill introduce a class
that does some input.

2
DemoInput.java

/
Created on Jan 20, 2004
_at_author Jerry Heuring
This class is used to demonstrate some
different input
methods for different types. It isn't the
best in all cases
but should get you started in this class. It
will depend
heavily on some of the class equivalents of
basic types.
/
import java.io.

3
Constructors

public class DemoInput
private BufferedReader inputSource
/
The constructor -- it would prefer to get a
BufferedReader
as it will support what we want to do in the
easiest way.
we can convert from other types to a
BufferedReader as well.
_at_param source The source for input for this
object.
/
public DemoInput(BufferedReader source)
inputSource source

/
Another constructor -- it gets an
InputStreamReader instead of
the BufferedReader.
_at_param inStrRdr An InputStreamReader to use
to do input
with this object.
/
public DemoInput(InputStreamReader inStrRdr)
inputSource new BufferedReader(inStrRdr)

/
A Constructor taking an Input Stream -- it
turns out that
System.in is an InputStream so that this will
be useful.
_at_param inStr The input stream to be used for
input by
this object.
/
public DemoInput(InputStream inStr)
inputSource new BufferedReader(new
InputStreamReader(inStr))

6
readLine Read a line

/
Reads a line from the input stream. It will
return an
empty string if an error (exception) occurs
during the
read.
_at_return The next line of the file or an empty
string
(on error).
/
public String readLine()
try
return inputSource.readLine()
catch (Exception e)
return ""

7
readInt reads an Integer

/
This routine will get a line and use the
parseInt routine
to convert it to an integer. It does handle
the empty string
by returning a zero.
_at_return The integer on the next line of the
file or zero
if an error occurs.
/
public int readInt()
String chunk
chunk readLine()
if (chunk "")
return 0
else
return Integer.parseInt(chunk)

8
readFloat read a float

/
Trying to do the same thing with a float. In
this case
I've decided to lose the String local and do
the conversion
directly. What happens if the read fails or
the conversion
fails?
_at_return The float on the next line of the
file or ??
/
public float readFloat()
return Float.parseFloat(readLine())

9
Main used for testing

/
The main program is going to try to test the
input routines
in the object. I'm not a big fan of this
class but it does
get us past some details and removes some
initial guesswork.
_at_param args The command line arguments. Not
used in this version.
/
public static void main(String args)
DemoInput testObject new DemoInput(System.in)
String line
int value
float floatValue

10
Main (continued)

System.out.println("Input a line to read ")
line testObject.readLine()
System.out.println("The line input was
"line)
System.out.println("Input an integer ")
value testObject.readInt()
System.out.println("The value returned was
"value)
System.out.println("Input a floating point value
")
floatValue testObject.readFloat()
System.out.println("The value returned was
"floatValue)
System.exit(0)

11
Program Design

UML version

12
Identify the Objects

DotCom
Company
Size
Hits
GameGrid
List of companies
Where the companies are placed
Oriented horizontal/vertical
Player
Turns/Guesses
Rating
Name

13
Decide on the Methods/Procedures

DotCom
Set/Get Name, Size, Hits
GameGrid
Initialize
Add Dot Com
Check For Hit
Dot Coms Left
Player
Take Turn
Play Game
Print Results

14
UML For the Problem -- Player
15
UML -- GameGrid
16
UML -- DotCom
17
Polymorphism Inheritance

Much of the power in object oriented programming
comes from polymorphism, inheritance, and
interfaces
Polymorphism is at the heart of all object
oriented programming languages. It is the
ability to treat different items in the same way.

18
An Example of Polymorphism

Assume you have a sound object, a movie object,
and a game object.
Because they are all objects they can be stored
in a vector or any other collection of objects.
Assuming they all have a play method (obviously
doing different things) we could put them in a
list, step through the list, and play each one.
(I just told a lie it isnt quite this simple
in Java but it is close)

19
Templates are not Polymorphism

Being able to handle different types of objects
in a consistent manner is part of polymorphism.
Polymorphism is NOT the same as a C template.
We are not creating a separate class for each
type of object.

20
Inheritance

In Java, C, and most (if not all) object
oriented languages you can inherit from another
class.
Consider it as extending or enhancing an
existing object. The existing object is still
there but more features have been added to it.

21
Inheritance Examples

You buy a computer system and add on some
specialized gaming equipment and I/O devices to
extend its capabilities.
The base computer system is still there it
could probably be used without all the new bells
and whistles youve added but the new object is
of more use.

22
More Inheritance

Another common use of inheritance is to allow
multiple objects share a common subset of methods
and attributes.

23
If You Look at Java There is All Kinds of
Inheritance Used

The Stack class extends the Vector Class
The Vector class extends the AbstractList class
The AbstractList class exteds the
AbstractCollection class
The AbstractCollection class extends the Object
class (All objects are descendents of the Java
Object class)

24
Opportunities for Inheritance

Two or more subclasses that might need common
behavior or that share some common underlying
data.

25
Is-a or Has-a?

The book sites the Is-a test as a method to
determine if something should be extended.
A vector is a list
A stack is a list (and in Javas case is a Vector
as well)
Has-a would mean that the object has an instance
variable of a given type.

26
Keep in Mind

A subclass extends its superclass
All public instance variables and methods are
inherited from the superclass. Private variables
and methods are not.
Inherited methods can be overridden. Instance
variables can be redefined but not overridden.

27
Interfaces

An interface is a group of calls/methods.
Anybody that implements the interface must
provide all the methods in the interface.
Objects implementing an interface dont need to
be a subclass of the same superclass but will
have a common set of methods.

28
Abstract Classes

Abstract classes can be used in a hierarchy and
as a type but cant be instantiated (created via
new).
Methods may also be abstract they have no body
and look like a function prototype in C.
Any class with an abstract method must also be
declared as abstract.

29
Where are Abstract Classes Used

Used heavily in the collections inside of Java to
enforce a common set of methods and of behavior.

30
An Example of Inheritance

/
_at_author Jerry Heuring
Created Jan 28, 2004
_at_version 0.0
Bugs
Revisions
This is a base class that will be used to help
keep
inventory at a "beverage" store. The base
class will
implement some of the functionality and the
subclasses
will add to it.
/
public class Beverage
private String name
private int size
private int numberInStock

/
_at_return returns the name of this beverage.
/
public String getName()
return name
/
_at_return the size in ounces of this beverage.
/
public int getSize()
return size
/
_at_return the quantity on hand of this beverage.
/
public int getNumberInStock()
return numberInStock

/
This routine allows you to change the amount
in stock.
A positive valued argument adds to stock on
hand and a
negative value removes stock (sale?). The
class clamps
stock to 0 -- can't have a negative amount of
stock.
_at_param delta The number of this item to
add/remove from stock.
_at_return the new stock level.
/
public int changeStock(int delta)
numberInStock numberInStock delta
if (numberInStock lt 0)
numberInStock 0
return numberInStock

33
Constructors

/
A complete constructor for the beverage class.
It
takes all the parameters and assigns them to
the
appropriate fields. Again, it clamps stock to
non-negative values.
_at_param name the name of this beverage
_at_param size the size of this beverage in
ounces
_at_param numberInStock the number of this
beverage in stock.
/
public Beverage(String name, int size, int
numberInStock)
this.name name
this.size size
this.numberInStock numberInStock
if (this.numberInStock lt 0)
this.numberInStock 0

/
The default constructor for the Beverage
class. The
default sets the name to an empty string, the
size
to zero ounces, and the quantity on hand to 0.
/
public Beverage()
this("", 0, 0)

35
toString() and main()

/
_at_return a printable representation of the
object as a string.
/
public String toString()
return name " " size " oz "
numberInStock " in stock"
/
The main program will run some testing code
exercising
the various functions of the class.
_at_param args The command line arguments. Not
used in
this version.
/

public static void main(String args)
Beverage bottle1 new Beverage()
Beverage bottle2 new Beverage("Coke", 12, 12)
Beverage bottle3 new Beverage("Coke", 12, 12)
/ check what the constructors did and examine
the
individual bottles using the toString
routine.
/
System.out.println(bottle1)
System.out.println(bottle2)
System.out.println(bottle3)
/ See if the two bottles are the same -- why?
/
if (bottle2 bottle3)
System.out.println("Bottles two and three are
the same")
else
System.out.println("Bottles two and three are
different?")

/ Check if changing stock works.
/
bottle2.changeStock(12)
bottle3.changeStock(-25)
/
Output the second bottle using the access
functions.
/
System.out.println("Name "bottle2.getName())
System.out.println("Size "bottle2.getSize())
System.out.println("Stock bottle2.getNumberIn
Stock())
/ Make sure the third bottle clamped stock at
0.
/
System.out.println(bottle3)
System.exit(0)

38
Next Level an AlcoholicBeverage

Adds in the alcohol content and the proof of the
beverage.

39
AlcoholicBeverage

/
_at_author Jerry Heuring
Created Jan 28, 2004
_at_version 0.0
Bugs
Revisions
A class for alcoholic beverages. It adds the
alcohol
content but might also override a sales
function (if
there is one) to check age/ID before selling
the alcohol.
/
public class AlcoholicBeverage extends Beverage
private double percentAlcohol
private double proof

40
Access Functions

/
_at_return the percentage of alcohol in this
beverage
/
public double getAlcohol()
return percentAlcohol
/
_at_return the "proof" level of the beverage
(double the alcohol)
/
public double getProof()
return proof

41
Constructors

/
This is a complete constructor -- it includes
the portions that
are contained in the super class as well as
those specific to
this class.
_at_param name the name of this beverage
_at_param size the size, in ounces, of this
beverage
_at_param numberOnHand the quantity on hand of
this beverage
_at_param percentAlcohol The percentage of
alcohol by volume in this beverage
_at_param proof the "proof" of this beverage
/
AlcoholicBeverage (String name, int size, int
numberOnHand, double percentAlcohol, double
proof)
super(name, size, numberOnHand)
this.percentAlcohol percentAlcohol
this.proof proof

/
A constructor with just the fields for this
class --
the superclass will be initialized with the
default
constructor in Beverage.
_at_param percentAlcohol the percentage of
alcohol by volume in this beverage
_at_param proof the "proof" level of this
beverage
/
AlcoholicBeverage (double percentAlcohol, double
proof)
this.percentAlcohol percentAlcohol
this.proof proof
/
The default constructor -- an alcohol free
beverage.
/
AlcoholicBeverage ()
this (0.0, 0.0)

43
Main()

/
The main program will run simple tests of the
class.
_at_param args the command line arguments -- not
used
/
public static void main(String args)
AlcoholicBeverage test1 new AlcoholicBeverage()
AlcoholicBeverage test2 new AlcoholicBeverage(1
2.0, 24.0)
AlcoholicBeverage test3 new AlcoholicBeverage("
Blatz", 12, 10, 4.5, 9.0)
System.out.println("Test 1 -- Fields")
System.out.println("Name "test1.getName())
System.out.println("Size "test1.getSize())
System.out.println("Stock " test1.getNumberI
nStock())
System.out.println("Alcohol "test1.getAlcohol()
)
System.out.println("Proof "test1.getProof())

System.out.println("Test 2 -- Fields")
System.out.println("Name "
test2.getName())
System.out.println("Size "
test2.getSize())
System.out.println("Stock "
test2.getNumberInStock())
System.out.println("Alcohol "
test2.getAlcohol())
System.out.println("Proof "
test2.getProof())
System.out.println("Test 3 -- Fields")
System.out.println("Name "
test3.getName())
System.out.println("Size "
test3.getSize())
System.out.println("Stock "
test3.getNumberInStock())
System.out.println("Alcohol "
test3.getAlcohol())
System.out.println("Proof "
test3.getProof())

System.out.println("Output of entire objects")
System.out.println("Test3 " test3)
System.out.println("Test2 " test2)
System.out.println("Test1 " test1)
System.exit(0)

46
Wine Class

/
_at_author Jerry Heuring
Created Jan 28, 2004
_at_version 0.0
Bugs
Revisions
This class inherits everything from the parent
class
(AlcoholicBeverage) and adds its own specific
fields
and methods. It isn't very complete but does
give a
start to the hierarchy.
/
public class Wine extends AlcoholicBeverage
private String varietal
private String vintner
private int vintage

47
Constructors

/
A Constructor with all parameters (including
those
needed for the superclasses AlcoholicBeverage
and
Beverage). This will call the super class
(must be
done first in a constructor) and the local
class to
do the initialization.
_at_param name the name of the beverage
_at_param size the size, in ounces, of the
beverage
_at_param numberOnHand The quantity on hand (in
units)
_at_param alcohol The percentage of alcohol in
the beverage
_at_param proof The proof level of the alcohol
_at_param vintner The vintner (maker) of the
wine.
_at_param varietal The types of grapes that are
in the wine
_at_param vintage The year the wine was made
/

public Wine (String name, int size, int
numberOnHand, double alcohol, double proof,
String vintner, String varietal, int vintage)
super(name, size, numberOnHand, alcohol, proof)
this.vintner vintner
this.varietal varietal
this.vintage vintage

/
A constructor with only the fields for this
particular class. The super classes will end
up
using their default constructors when the
instantiation takes place.
_at_param vintner The producer of the wine
_at_param varietal The variety or varieties of
grapes
used in the wine
_at_param vintage The year the wine was produced
/
public Wine(String vintner, String varietal,
int vintage)
this.vintner vintner
this.varietal varietal
this.vintage vintage

/
The default constructor. Sets some initial
values.
/
public Wine()
this("", "", 0)

51
The Access Functions

/
_at_return The maker of this wine.
/
public String getVintner()
return vintner
/
_at_return This wines variety
/
public String getVarietal()
return varietal
/
_at_return The year this wine was made.
/
public int getVintage()
return vintage

/
Convert the object to some output friendly
version.
_at_return a printable version of the object.
/
public String toString()
return vintner ", " varietal ", "
vintage " ( " getNumberInStock() " ) "

53
Main()

/
The main program is being used to test the
methods
in the class. It will exercise all 3
constructors
as well as the access methods.
_at_param argsThe list of command line arguments
(not used)
/
public static void main(String args)
Wine bottle1 new Wine()
Wine bottle2 new Wine("Old Fart",
"Merlot Cabernet", 1991)
Wine bottle3 new Wine("Gallo", 32, 144, 12.0,
24.0, "Gallo", "Pinot Grigio", 1992)
System.out.println("Bottle 1 " bottle1)
System.out.println("Bottle 2 " bottle2)
System.out.println("Bottle 3 " bottle3)