Transcript javaProgLec06

Exceptions:
Checked versus Unchecked
Exceptions
Probable Source
Within Probable
your
Source
control
Error
NO
RuntimeExce YES
ption
All other
NO
exceptions
Checked
System
NO
Programmer NO
User
YES
Example of Error: System-out-of-memory Error
Examples of RuntimeException: ClassCastException, NumberFormatException.
Example of checked Exceptions: EOFExcception,
Situations which cause Exceptions
(or Errors) to be thrown
• An internal Error occurs in the VM
(OutOfMemoryError)
• An unchecked Exception is generated and
thrown (ArrayIndexOutOfBounds)
• A checked Exception is thrown (EOFException)
• You purposefully throw an Exception.
Exception sequence
• Once an exception is generated, the execution
sequence immediately terminates until the
exception is caught (or propagates up the call
stack to the VM). In practice that means that
any code following your statement which
threatens to throw an exception will NOT be
executed if an exception occurs. No return
value!
• An exception is thrown up the call stack
Some Java naming wierdness in the
Exception Handling API
• Despite having the 'able' suffix, Throwable is a
class, not an interface.
• Errors are considered part of the "Exception
Handling" API
• All Exceptions and Errors occur at Runtime, so
RuntimeException is a useless name.
Some things to remember about
Exceptions
• Anything that inherets from RuntimeException
is unchecked.
Event Model in Java
Intro to Data Structures in Java
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•
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Single Lined List
Stack
Binary Tree
others...
"If I can't picture it, I
can't understand it."
Source Code Online
• Please avail yourselves of the many excellent
sources for source code, both full applications
and snippets.
• http://stackoverflow.com/ (best for snippets)
• http://www.planet-source-code.com/ (best
for full apps)
• http://www.freewarejava.com/
• http://www.javagalaxy.com/
• http://www.java2s.com
• http://www.javadb.com/
Guidelines for using found source code
• If you know the URL where you got it, cite like
so:
– //http://stackoverflow.com/questions/26305/how
-can-i-play-sound-in-java
– At minimum, cite the domain:
– //method found on stackoverflow.com
• Don't copy an entire application; that is
plagiarism.
• Use found source code within reason.
Cross-Cutting Concerns
BlackJack
• Exceptions
• Assertions
• Logging
Shoe
Dealer
Inner and Anonymous Classes
• Though you are captive in the OO paradigm,
you can use inner classes and anonymous
classes to get around this constraint and write
procedural-like code.
• Often times, no one but the enclosing class
cares about an object. In this case, you may
consider using inner or anonymous classes.
Intro to Data Structures in Java
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•
•
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Single Lined List
Stack
Binary Tree
others...
WindowsBuilderPro by Google
• b,y,c,n,s,l,d,f,str; get rid of these in Window ||
Preferences || Java || Code Style || Fields.
Otherwise, they will hose you in WB.
Constructors
• Constructors are optional. If your class is just a static
driver; i.e. it just has a static main method, then no
need to instantiate it; and no need for constructor.
• If your class is a "java bean" -- a class that models a
real world object (noun) in your system, then it
should have a constructor. House, Car, Person, etc.
• If you don't provide a constructor, a no-args
constructor is provided automatically.
• You can, and often want, more than one constructor
with different signatures.
• You call a constrcutor with the 'new' keyword.
Model a system
• Object-oriented programming is about
modeling a system.
• Write the problem out as requirements -- this
will essentially be a math world problem (your
favorite kind to solve!)
• Your computer objects map directly to realworld objects (nouns).
• Your methods map directly to real-world
actions (verbs).
Write a very simple application for a contact manager. The the sake of
simplicity, each contact will have a name and a phone number only. The
user should be able to create new contacts and diplay all contacts.
Build a GUI using WindowBuilder and Swing.
Write a very simple application for computer dictionary. The the sake of
simplicity, each entry has a word and a definition. Store the pair in an
ArrayList<DictEntry>. Each DictEntry has two strings.
Build a GUI using WindowBuilder and Swing.
Describe the system:
The game of BlackJack; a single player plays against the house for money.
His bet is consistently $100.00 and he starts with 1,000.00. There is a shoe
of six 52-card decks which is reshuffled when the shoe is half used. If the
player wins the hand, his gets his bet back plus the amount of the bet. If he
loses, he loses the money, and if he gets blackjack, he get's his bet * 1.5.
The player plays against a dealer who must follow the following strict rules;
aces are worth 11points only, and the dealer must hit on 16 or below. The
player however, is allowed to hit or hold on any hand-value. Furthermore,
aces are worth either 1 or 11, whichever is more advantageous.
An initial two hands are dealt on seperate sides of a table consisting of two
cards apiece. The dealer's hand displays only one card up. The player has
the option to hit, hold, split, double-down, buy insurance, etc. For this
initial version of the game, we'll consider only hit, hold, and deal.
blue are nouns (objects or fields)
red are verbs (methods)
Interfaces
• A class implements an interface rather than
extends it. Any class that implements the
interface must override all the interface
methods with it's own methods.
• Interface names often end with "able" to
imply that they add to the capabilty of the
class.
• An interface is a contract; it defines the
methods
CORRECT