Advanced Programming in Java

1. Advanced Programming in Java Peyman Dodangeh Sharif University of Technology Fall 2013 Lecture 1: Introduction to OOP Slides adapted from Steven Roehrig

2. Expected Background • “A one-semester college course in programming.” • I assume you can write a program in some language, understand variables, control structures, functions/subroutines. • If in doubt, let’s talk.

3. Course Outline • Week 1: Background, basics of O-O, first Java program, programming environments • Week 2: Raw materials: types, variables, operators, program control • Week 3: Classes: declarations, constructors, cleanup & garbage collection • Week 4: Packages, access specifiers, finals, class loading

4. Course Outline (cont.) • Week 5: Polymorphism, abstract classes, design patterns • Week 6: Interfaces & extends, inner classes, callbacks via inner classes • Week 7: Applets, Applications, Swing • Week 8: Graphics and Multimedia • Week 9: Arrays, container classes, iterators

5. Course Outline (cont.) • Week 10: Exception handling, threads • Week 11: Java I/O, networking • Week 12: JDBC and object persistency

6. Administrative Details (cont.) • Midterm and final exams • Homework + Quiz + Projects: 50% • Midterm exam: 20% • Final exam: 30% • I will give one A+.

7. Administrative Details (cont.) • Everything is attached to the syllabus. Don’t look for assignments, etc. on Blackboard. Look at the syllabus! • Homework usually weekly. • Submission instructions with each assignment, usually printed listings and a zip file. • Printing slides? Three to a page, at least. Save a tree! Remove the PowerPoint background before printing. Save toner!

8. Administrative Details (cont.) • Attendance is not required, but… • …you are responsible for everything said in class. • I encourage you to ask questions in class. Don’t guess, ask a question!

9. My Policy on Cheating • Cheating means “submitting, without proper attribution, any computer code that is directly traceable to the computer code written by another person.” • I give students a failing course grade for any cheating. • This doesn’t help your job prospects.

10. My Policy on Cheating • You may discuss homework problems with classmates, after you have made a serious effort in trying the homework on your own. • You can use ideas from the literature (with proper citation). • You can use anything from the textbook/notes. • The code you submit must be written completely by you.

11. Course Etiquette • Etiquette is “conduct in polite society” • No cell phones • No random comings and goings • If you are sleepy, go home • If you want to read email or surf the Web, please do it elsewhere

13. Object Oriented Programming • Problem Space • the place where the problem exists • such as a business • Solution Space • the place where you’re implementing that solution • such as a computer • The effort required to perform this mapping. • E.g. think about a library, or a phonebook program

14. Object Oriented Approach • OOP lets the programmer represent problem space elements • The elements in the problem space and their representations in the solution space are referred to as “objects”

15. OOP • The program is allowed to adapt itself to the lingo of the problem • by adding new types of objects • when you read the code, you’re reading words that also express the problem.

16. OOP (2) • OOP allows you to describe the problem in terms of the problem • Rather than in terms of the computer • Objects in your code are similar to real objects • Recall the sample programs: phonebook and library

17. O-O Languages (Alan Kay) • Everything is an object. • A program is a bunch of objects telling each other what to do, by sending messages. • Each object has its own memory, and is made up of other objects. • Every object has a type (class). • All objects of the same type can receive the same messages.

18. Objects • An object has an interface, determined by its class. • A class is an abstract data type, or user-defined type. • Designing a class means defining its interface.

19. Built-In Types • Think of an int… • What is its interface? • How do you “send it messages”? • How do you make one? • Where does it go when you’re done with it? • In solving a computational problem, the goal is to • Dream up useful classes, and • Endow them with appropriate characteristics.

20. Example • Suppose I’ve defined this class in Java: • To make one, I type Light lt = new Light(); • If I want switch on My Lamp, I say lt.on();

21. But Why Not Just… Light lt; • This is legal, but just makes a “reference variable” named lt • This variable can refer to anyLight object, but currently refers to nothing • The operator new actually causes an object to be created, so we tell it what kind we want

22. Designers Design, Users Use • The interface is the critical part, but the details (implementation) are important too. • Users use the interface (the “public part”); the implementation is hidden by “access control”.

23. Object Oriented Languages • Smalltalk • The first successful object-oriented language • One of the languages upon which Java is based • Java • C++ • C##

24. Why So Many Languages? • Bring the language “closer” to the problem. • But 4GLs are typically focused on specialized domains (e.g., relational databases). • We want a language that is general purpose, yet can easily be “tailored” to any domain.

25. Java History • Java was created in 1991 • by James Gosling in Sun Microsystems • Initially called Oak • in honor of the tree outside Gosling's window • Its name was changed to Java • because there was already a language called Oak. • Sun Microsystems released the first public implementation as Java 1.0 in 1995 • Java syntax is similar to C and C++.

26. Java Motivation • The need for platform independent language • To be embedded in various consumer electronic products • like toasters and refrigerators • Platform independent?! • Hardware • Operating System

27. Java Motivation (2) • At the same time, the World Wide Web and the Internet were gaining popularity. • Java could be used for internet programming. • Why? • Platform independence • Creation of Applets

28. The Java technology is: • A programming language • Java can create all kinds of applications • A development environment • A compiler (javac) • An interpreter (java) • A documentation generator (javadoc) • … • Compare it to C++

29. High-Level Languages

30. Java Virtual Machine

31. Compile and Execution Stages • Compare to C++ and Assembly • .NET Framework Sharif University of Technology

32. Java is Popular • Some reports on programming languages popularity • According to • Job advertisements • Book sales • Finding code on the web • …

33. Characteristics of Java • Java is simple • Java is object-oriented • Java is architecture-neutral • Java is portable • Java is interpreted • Java is multithreaded • Java is secure • Java is robust

34. First Example • Create a file named First.java • Java class files have .java extension • Note to naming convention • Copy this lines to the file • Note: File name and class name should be the same.

35. The Major Issues • Editing • Use any text editor you like (not a word processor!); save as HelloDate.java • Compiling • From a DOS or UNIX command line, type > javac HelloDate.java • This should produce the file HelloDate.class • Running • Again from the command prompt, type > java HelloDate

36. Assignment # 0 • Download and install JDK • http://www.oracle.com/technetwork/java/javase/downloads/index.html • JDK 7 • Write a program that prints your name on the console • Compile and run the program

37. Further Reading • Read Java page on Wikipedia http://en.wikipedia.org/wiki/Java_(programming_language) • Google this terms and phrases: • Java • Java Mobile • JVM • Byte code • Java Sun • Java and C++ • Java and C#

38. The End.