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. 2

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. CS 340 3

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. CS 340 4

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:  Software is not just coding… It is design, performance, memory consumption It is an art, a riddle to be solved with every project CS 340 5

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 webpagewebpage  Reading and examples will be posted online.  Check the webpage for news frequently. CS 340 6

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… CS 340 7

Grading  Homework and Programming projects will be posted online CS 340 8

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 CS 340 9

Principles of Pair Programming CS

12 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. CS 340

13 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. CS 340

Policies  Read the collaboration policy carefully.  Late policy:  1 st day late: 10% off  10% is reduced by every day the homework is late CS

Java… a bit of history CS

16 Java timeline  CS 340

17 Java Design Goals  Simple, object oriented, and familiar  Robust and secure  Architecture neutral and portable  High performance  Interpreted, threaded, and dynamic CS 340

17 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. CS 340

OOP or… Object Oriented Programming 18 CS 340

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 CS

20 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?” CS 340

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() CS

A Superclass and Subclass Example  Robot  A robot has a  manufacturer  processor  disk  parts  processor speed CS Write the robot class

A Superclass and Subclass Example (cont.)  Robot  A robot has a  manufacturer  processor  disk  parts  processor speed Robot String manufacturer String processor int diskSize int numberOfParts double processorSpeed CS

A Superclass and Subclass Example (cont.) Robot String manufacturer String processor int diskSize int numberOfParts double processorSpeed int getDiskSize() double getProcessorSpeed() int getParts() String toString() CS

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) CS What is a Cylon class?

A Superclass and Subclass Example (cont.) Cylon double pixels double battleSpeed Robot String manufacturer String processor int diskSize int numberOfParts double processorSpeed int getDiskSize() double getProcessorSpeed() int getParts() String toString() CS

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) CS

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; } 28 Write the methods’ code

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; } CS

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; } CS

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 CS

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 CS

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 CS