Chapter 1 Overview

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Chapter 1 Overview

• James Chen
• 2005/9/19

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Outlines

• What are Data Structures and Algorithms Good for?
• Overview of Data Structures
• Overview of Algorithms
• Some Definitions
• Object-Oriented Programming
• Software Engineering
• Java for C Programmers
• Java Library Data Structures - Collections

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This chapter will answer

• What are data structures and algorithms?
• What good will it do me to know about them?
• Why can't I just use arrays and for loops to
  handle my data?
• When does it make sense to apply what I learn
  here?

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What are data structures and algorithms?

• Data Structures are arrangement of data in a
  computers memory (or sometimes on a disk).
• Include arrays, linked lists, binary trees, and
  hash tables.
• Algorithms manipulate the data in these
  structures in various ways
• Searching for particular data item sorting the
  data, .

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What are Data Structures and Algorithms Good for?

• You can apply them to solve
• Real-World data storage ( for User)
• Personal record
• Index cards
• Data base
• Programmers Tools (for Program)
• Stacks, Queues, priority queues,
• Real-World Modeling
• Graph for airline routes between cities

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Cardfile
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Overview of Data Structures
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Overview of Algorithms

• Many of the algorithms we'll discuss apply
  directly to specific data structures.
• Insert a new data item.
• Search for a specified item.
• Delete a specified item.
• May also need to know how to iterate through all
  the items in a data structure
• visiting each one in turn so as to display it or
  perform some other action on it.
• Most Important Algorithm Sorting (Ch37)
• Recursion is also important for designing some
  algorithm. (Ch6)

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Some Definitions

• Database to refer to all the data that will be
  dealt with in a particular situation.
• Record the units into which a database is
  divided.
• Field A Record is usually divided into several
  fields.
• Key To search for a record within a database you
  need to designate one of the record's fields as a
  key (search key).

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Key, Search key
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Object Oriented Programming

• Basic introduction to OOP
• See Appendix B for future reading
• OOP was invented because procedural languages,
  such as C, Pascal, and BASIC, were found to be
  inadequate for large and complex programs.
• Lack of correspondence between the program and
  the real world.(??????????!)
• Internal organization of the program.(?????,
  ??,??,????????????)

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Problems with Procedural Languages

• Poor Modeling of the Real World
• Difficult to model the real-word using procedural
  language.
• Functions carry out a task, while data
  (variables) stores information, but most
  real-world objects do both these things.
• Large programs may be difficult to implement.
• Crude Organizational Units
• Procedural programs are organized by dividing the
  code into functions (methods).
• Focus on functions.
• Variables Local variables (within methods) and
  Global variables (whole program) without other
  choose !?
• Local v.s. global variable ?
• Solution ?? ? OOP

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Objects in a Nutshell

• An object contains both functions and variables.
  ( Encapsulation )
• Functions are called methods and variables are
  called fields.
• OOP solves several problems simultaneously.
• A programming object correspond more accurately
  to objects in the real world.
• Solve issue of global data in the procedural
  model.

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Objects in a Nutshell

• A class is a specification - a blueprint - for
  one or more objects.

class Thermostat private float
currentTemp private float desiredTemp
public void furnace_on() // method body
goes here public void furnace_off()
// method body goes here // end
class Thermostat
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Objects in a Nutshell

• Creating Object new XXX()
• Allocate memory for store information.

Thermostat therm1, therm2 // create two
references therm1 new Thermostat() // create
two objects and therm2 new Thermostat() //
store references to them
therm2
therm1
0x1020
0x1000
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Objects in a Nutshell

• Accessing Objects Methods

therm2.furnace_on()
System.out.println(therm2.currentTemp)
therm2
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A Runnable Object-Oriented Program

• Reference page 11 12

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Some notes for BankApp

• Constructors
• A constructor is a special method that's called
  automatically whenever a new object is created.
• A constructor allows a new object to be
  initialized in a convenient way.
• A constructor always has exactly the same name as
  the class
• You can have many constructors with different
  signatures. ( overloading )
• Access modifiers
• determine what methods can access a method or
  field.
• Keywords public, private, protected, ltdefaultgt

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Some notes for OOP

• Encapsulation ? Nature, Robustness, Reusing !
• Class access control
• Inheritance (subclassing) ? Reusing !
• Inheritance is the creation of one class, called
  the extended or derived class (subclass), from
  another class called the base class(Super class).
• The extended class has all the features of the
  base class, plus some additional features.
• Polymorphism ? Extensibility Flexibility !
• Polymorphism involves treating objects of
  different classes in the same way.
• these different classes must be derived from the
  same base class.
• Polymorphism simplifies and clarifies program
  design and coding.

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Software Engineering

• Reference to BCC

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????(??)
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Java for C Programmers

• Study it carefully by yourself if you are
  interested to this topic.
• Key issues
• Reference and Pointers (no pointer).
• new operator and Garbage collection for memory
  (object) management.
• Difference between and equals()
• Primitive data-type and reference data-type
• How to handle Input and Output?

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Java Library Data Structures

• Java Collection, some pre-defined classes
• java.util.
• Vector, Dictionary, Stack, Hashtable,
• In this book we'll largely ignore these built-in
  classes.
• We're interested in teaching fundamentals, not in
  the details of a particular data-structure
  implementation.
• Reference to the collection book, Java
  Collections An Introduction to Abstract Data
  Types, Data Structures and Algorithms

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End of Chapter 1