CS 340 DATA STRUCTURES

Instructor: Xenia Mountrouidou

Course Objectives

At the end of this class you will be able to: Make design decisions on which data

structure is best to use regarding performance, memory, and implementation efficiency.

Devise or use the most efficient algorithm in your projects.

Understand algorithmic complexity. Think analytically and identify complexity of

a program.

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Course Objectives (cont.)

At the end of this class you will be able to: Apply object oriented programming

principles when you develop software. Use and understand third party code. Detect inefficiency of data structures and

algorithms of third party code. Develop projects using agile test driven

approach (Junit). Employ the Java API.

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Why do you need CS 340?

Scenario: You are a senior developer for e-bay. You are working on their e-commerce

application server! You drop code, you are a java guru, OO

programming is second nature to you… but you do not understand data structures and algorithms.

BIG DEAL! Everything runs perfectly. Until one day…

You need to use a sorting algorithm to sort all potential sellers of a product based in price or ranking.

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Why do you need CS 340?

Scenario (cont.): On every click for a product search, your

sorting algorithm will be used. You choose bubble sort. After all, it has a

cool name! Let’s see what happens: http

://www.cs.bu.edu/teaching/alg/sort/demoSoftware is not just coding… It is design, performance, memory consumptionIt is an art, a riddle to be solved with every project

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Lectures

We meet at 15:00-16:45, every Tues/Thurs, at Merritt Penticoff Science Bld, Room 130

Attendance will have a part in your grade. Attendance means: active participation!

Check the schedule in our webpage Reading and examples will be posted

online. Check the webpage for news frequently.

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How to get help

Join my office hours! Join the conversation on Piazza. Check our website frequently. Use the textbook:

“Data Structures: Abstraction and Design Using Java”, Second Edition by Elliot B. Koffman, Paul A. T. Wolfgang

Experiment with code. It’s fun…

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Grading

Midterm exam 20%Final exam 20%Homeworks 25%Programming projects 25%Class participation 10%Total 100%

Homework and Programming projects will be posted online

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Programming Projects

They involve Design Coding Testing Debugging

Some of these can be done in pairs Both team members will need to answer

detailed questions about the implementation

Each team member will evaluate his/her team mate

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Principles of Pair Programming

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Principles of Pair Programming All I Really Need to Know about pair

programming I Learned in Kindergarten Share everything. Play fair. Don’t hit people. Put things back where you found them. Clean up your own mess. Don’t take things that aren’t yours. Say you’re sorry when you hurt somebody.

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Principles of Pair Programming

Wash your hands before you eat. Flush. Warm cookies and cold milk are good for

you. Live a balanced life – learn some and think

some and draw and paint and sing and Dance and play and work every day some. Take a nap every afternoon. When you go out into the world, watch out

for traffic, hold hands and stick together. Be aware of wonder.

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Policies

Read the collaboration policy carefully. Late policy:

1st day late: 10% off 10% is reduced by every day the homework

is late

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Java… a bit of history

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Java timeline

http://www.youtube.com/watch?v=WAy9mgEYb6o

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Java Design Goals

Simple, object oriented, and familiar Robust and secure Architecture neutral and portable High performance Interpreted, threaded, and dynamic

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Java abbreviations

JDK: Java Development Kit JSDK: Java Servlet Development Kit JVM: Java Virtual Machine J2EE: Java Platform, Enterprise Edition. A

widely used platform for server programming.

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OOP or… Object Oriented Programming18

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Object-Oriented Programming Object-oriented programming (OOP) is

popular because: enables reuse of previous code saves time

If a new class is similar to an existing class, the existing class can be extended

This is called inheritance

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Java is object oriented

Old programming languages: code was executed line by line and

accessed variables or records Java

objects that come with their own methods When coding in Java one is always

thinking about “which object is running this code?”

Inheritance

Meat is a Food Meat has all the data

fields and methods defined by Food

Food is the superclass of Meat

Meat is a subclass of Food

Meat may define other variables and methods that are not contained in Food

Food

expirationDate()

Meat

percentageOfProtein()

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A Superclass and Subclass Example

Robot A robot has a

manufacturer processor disk parts processor speed

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Write the robot class

A Superclass and Subclass Example (cont.)

Robot A robot has a

manufacturer processor disk parts processor speed

Robot

String manufacturerString processorint diskSizeint numberOfPartsdouble processorSpeed

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A Superclass and Subclass Example (cont.)

Robot

String manufacturerString processorint diskSizeint numberOfPartsdouble processorSpeed

int getDiskSize()double getProcessorSpeed()int getParts()String toString()

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A Superclass and Subclass Example (cont.)

Cylon A Cylon has all the

properties of Robot, manufacturer processor disk parts processor speed

plus, vision (pixels) hands (battle speed)

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What is a Cylon class?

A Superclass and Subclass Example (cont.)

Cylon

double pixelsdouble battleSpeed

Robot

String manufacturerString processorint diskSizeint numberOfPartsdouble processorSpeed

int getDiskSize()double getProcessorSpeed()int getParts()String toString()

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A Superclass and Subclass Example (cont.)

The constructor of a subclass begins by initializing the data fields inherited from the superclass(es)

super(man, proc, parts, disk, procSpeed);

which invokes the superclass constructor with the signature

Robot(String man, String processor, int parts, int disk, double procSpeed)

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A Superclass and Subclass Example (cont.)

/** Class that represents a robot */

public class Robot {

private String manufacturer;

private String processor;

private int numParts;

private int diskSize;

private double processorSpeed;

public Robot(String man, String processor, int numParts, int disk, double procSpeed) { //constructor

manufactuer = man;

this.processor = processor;

this.numParts = numParts;

diskSize = disk;

processorSpeed = procSpeed;

}

}

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Write the methods’

code

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A Superclass and Subclass Example (cont.)

public double getProcessorSpeed() { return processorSpeed; }

public int getDiskSize() { return diskSize; }

public int getParts() { return numParts; }

public String toString() {

String result = "Manufacturer: " + manufacturer + "\nCPU: " + processor + "\nBody parts: " + numParts + "\nDisk: " + diskSize + " gigabytes" + "\nProcessor speed: " + processorSpeed + " gigahertz";

return result;

}

}

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A Superclass and Subclass Example (cont.)

public class Cylon extends Robot

{

private double pixels;

private double battleSpeed;

public Cylon(String man, String processor, int parts, int disk, double procSpeed, double pix, double bSpeed) {

super(man, proc, parts, disk, procSpeed);

pixels = pix;

battleSpeed = bSpeed;

}

}

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Protected Visibility for Superclass Data Fields

Variables with private visibility (defined by the keyword private) cannot be accessed by a subclass

Variables with protected visibility (defined by the keyword protected) are accessible by any subclass or any class in the same package

By default variables are public, i.e., they can be accessed by any package

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Is-a versus Has-a Relationships In an is-a or inheritance relationship, one

class is a subclass of the other class In a has-a or aggregation relationship,

one class has the other class as an attribute

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Is-a versus Has-a Relationships (cont.)

public class Robot { private Memory mem; ...}

public class Memory { private int size; private int speed; private String kind; ...}

A Robot has only one Memory

But a Robot is not a Memory (i.e. not an is-a

relationship)

If a Cylon extends Robot,then the Cylon

is-a Robot

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