1 / 19
Télécharger la présentation

Java Programming Essentials: Insights and Fundamentals

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Java Environment (CSS444) • Introduction • Object Oriented Programming Concepts • Basics for Java Applications • Basics for Java Applets • Control Structures • Methods • Arrays • Object Oriented Programming • Inheritance, Superclasses, Subclasses, Polymorphism, Abstract and concrete classes • Strings and Characters • Exception Handling • Files and Streams • Java Database Connectivity

  2. Chapter 1 - Introduction to Computers, the Internet, and the World Wide Web Outline 1.1 Introduction 1.3 Computer Organization 1.4 Evolution of Operating Systems 1.5 Distributed and Client/Server Computing 1.6 Machine Languages, Assembly Languages and High-Level Languages 1.8 History of Java 1.9 Java Class Libraries 1.10 Other High-Level Languages 1.11 Structured Programming 1.13 Basics of a Typical Java Environment 1.14 General Notes about Java and This Book

  3. 1.1 Introduction • Java • Powerful, object-oriented language • Fun to use for beginners, appropriate for experienced programmers • Language of choice for Internet and network communications • Free implementation at http://java.sun.com

  4. 1.3 Computer Organization • Six logical units in every computer • Input unit • Gets information from input devices (keyboard, mouse) • Output unit • Gets information (to screen, to printer, to control other devices) • Memory unit • Rapid access, low capacity, stores input information • Arithmetic and logic unit (ALU) • Performs arithmetic calculations and logic decisions • Central processing unit (CPU) • Supervises and coordinates the other sections of the computer • Secondary storage unit • Cheap, long-term, high-capacity storage, stores inactive programs and data

  5. 1.4 Evolution of Operating Systems • Batch processing • Doonly one job or task at a time • Operating systems • Manage transitions between jobs • Increased throughput - amount of work computers process • Multiprogramming • Many jobs or tasks sharing the computer resources • Timesharing • Runs a small portion of one user’s job then moves on to service the next user • Programs appear to be running simultaneously

  6. 1.5 Distributed and Client/Server Computing • Distributed computing • Organization has a Local Area Network (LAN) • Computers linked to it • Computing distributed over the LAN, rather than at one central location

  7. 1.5 Distributed and Client/Server Computing • Client/Server computing • File servers offer common store of programs that client computers access • C and C++ popular for writing operating systems, networking, and distributed client/server applications • Java used for Internet-based applications

  8. 1.6 Machine Languages, Assembly Languages and High-Level Languages • Types of programming languages • Machine languages • Strings of numbers giving machine specific instructions • Example: +1300042774+1400593419+1200274027 • Assembly languages • English-like abbreviations representing elementary computer operations (translated via assemblers) • Example: LOAD BASEPAY ADD OVERPAY STORE GROSSPAY

  9. 1.6 Machine Languages, Assembly Languages and High-Level Languages • Types of programming languages 3. High-level languages • Similar to everyday English and use mathematical notations (translated via compilers) • Example: grossPay = basePay + overTimePay

  10. 1.8 History of Java • Java • Based on C and C++ • Originally developed in early 1991 for intelligent consumer electronic devices • Market did not develop, project in danger of being cancelled • Internet exploded in 1993, saved project • Used Java to create web pages with dynamic content • Java formally announced in 1995 • Now used to create web pages with interactive content, enhance web servers, applications for consumer devices (pagers, cell phones)...

  11. 1.9 Java Class Libraries • Java programs • Consist of pieces called classes • Classes contain methods, which perform tasks • Class libraries • Also known as Java API (Applications Programming Interface) • Rich collection of predefined classes, which you can use • Two parts to learning Java • Learning the language itself, so you can create your own classes • Learning how to use the existing classes in the libraries

  12. 1.10 Other High-Level Languages • A few other high-level languages have achieved broad acceptance • FORTRAN (FORmula TRANslator) • Scientific and engineering applications • COBOL (COmmon Business Oriented Language) • Used to manipulate large amounts of data • Pascal • Intended for academic use • BASIC • Developed in 1965 as a simple language to help novices

  13. 1.11 Structured Programming • Structured programming • Disciplined approach to writing programs • Clear, easy to test and debug, and easy to modify • Pascal designed to teach structured programming in universities • Not used in industrial or commercial applications • Multitasking • Specifying that many activities run in parallel • C and C++ only allow one activity to be performed at a time • Java allows multithreading, where activities can occur in parallel

  14. 1.13 Basics of a Typical Java Environment • Java Systems • Consist of environment, language, Java Applications Programming Interface (API), Class libraries • Java programs have five phases • Edit • Use an editor to type Java program • vi or emacs, notepad, Jbuilder, Visual J++ • .java extension • Compile • Translates program into bytecodes, understood by Java interpreter • javac command: javac myProgram.java • Creates .class file, containing bytecodes (myProgram.class)

  15. 1.13 Basics of a Typical Java Environment • Java programs have five phases (continued) • Loading • Class loader transfers .class file into memory • Applications - run on user's machine • Applets - loaded into Web browser, temporary • Classes loaded and executed by interpreter with java command java Welcome • HTML documents can refer to Java Applets, which are loaded into web browsers. To load, appletviewer Welcome.html • appletviewer is a minimal browser, can only interpret applets

  16. 1.13 Basics of a Typical Java Environment • Java programs have five phases (continued) • Verify • Bytecode verifier makes sure bytecodes are valid and do not violate security • Java must be secure - Java programs transferred over networks, possible to damage files (viruses) • Execute • Computer interprets program one bytecode at a time • Performs actions specified in program • Program may not work on first try • Make changes in edit phase and repeat

  17. Disk Disk Interpreter Compiler Editor Bytecode Verifier Class Loader . . . . . . . . . . . . . . . . . . Program is created in the editor and stored on disk. Phase 1 Compiler creates bytecodes and stores them on disk. Phase 2 Primary Memory Phase 3 Class loader puts bytecodes in memory. Disk Primary Memory Phase 4 Bytecode verifier confirms that all bytecodes are valid and do not violate Java’s security restrictions. Primary Memory Interpreter reads bytecodes and translates them into a language that the computer can understand, possibly storing data values as the program executes. Phase 5

  18. 1.14 General Notes about Java and This Book • Java • Powerful language • Programming notes • Clarity - Keep it Simple • Portability - Java very portable, but it is an elusive goal • Performance • Interpreted programs run slower than compiled ones • Compiling has delayed execution, interpreting executes immediately • Can compile Java programs into machine code • Runs faster, comparable to C / C++

  19. 1.14 General Notes about Java and This Book • Just-in-time compiler • Midway between compiling and interpreting • As interpreter runs, compiles code and executes the program in the machine language rather than reinterpreting. • Not as efficient as full compilers • A full compiler is being developed for Java • Integrated Development Environment (IDE) • Tools to support software development • Several Java IDE's are as powerful as C / C++ IDE's NEXT: * Object-Oriented Programming Concepts

More Related