A BRIEF HISTORY OF OOP AND JAVA PROGRAMMING LANGUAGE

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A BRIEF HISTORY OF OOP AND JAVA PROGRAMMING
LANGUAGE

• Ziya Karakaya
• Atilim University
• Tel [phone] / 5345 Faks (312) 460 20
  37
• E-posta ziya_at_atilim.edu.tr

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History of Object-Oriented Programming Languages

• Almost all major concepts of OOP, such as
  objects, classes, and inheritance hierarchies,
  were developed in the 1960s
• Simula language, by Norwegian Computing Center
• In the 1970s, Alan Kay developed Smalltalk
  language at Xerox PARC (the Palo Alto Research
  Center)
• targeted to be understandable to people with no
  prior training in computer use
• demonstrated by experiments conducted using
  children as programmers

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History (contd)

• Bjarne Stroustrup at Bell Labs who had learned
  Simula during his Ph.D. studies developed C as
  an extension of C
• Later many other OOP languages were developed
  Eiffel, Objective-C, Actor, Object Pascal, etc.
• Since 1986 (first OOPSLA conference) OOP is a
  mainstream player in the PL domain the rather
  than a revolutionary one.

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Why Java ?

• We will explore the OOP in the context of Java
  programming language.
• OOP has been a hot topic for over a decade
• Java has recently become the commonly perceived
  embodiment of object-oriented ideas

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Java Programming Language

• Java is a general purpose programming language
  that can be used to create almost any type of
  computer program.
• Especially, it can be used to create programs
  intended for execution across the Internet.

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The History of Java

• It was named Oak in 1991 at Sun Microsystems.
• A computer scientist, James Gosling, developed
  Oak for use in embedded consumer electronic
  applications, such as VCRs.
• This development purpose has determined many of
  the characteristics of the language.
• Size and reliability are key features.
• The processors that run in embedded systems are
  very small and has very little memory. A program
  must be able to be translated into a very concise
  encoding.
• Embedded systems should almost never fail.

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• Java has these features.
• Pointers and goto statement were eliminated.
• Exception-handling is enforced to handle the
  unexpected in a graceful fashion
• Unfortunately, Java (or Oak) as a language for
  embedded consumer electronics did not materialize
  at that time!

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Evolution of World Wide Web

• World Wide Web was developed in the early 1990s
  by a small group of scientists at a research lab
  in Switzerland.
• As a mean of quickly communicating research
  results to a physically far-flung set of
  colleagues.
• To understand how Java fits into the WWW, one
  must understand about the concepts of clients and
  servers and the difference between server-side
  computing and client-side computing.

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Client-Side Computing

• The Internet is a classic example of a
  client/server system.
• A person using the Internet works at his or her
  own computer, which runs an Internet-aware
  application, such as a Web browser. This is
  called the client system.
• The client application communicates over the
  Internet with another computer. For example, a
  Web browser might request the information on a
  Web page stored on a distant computer.
• This computer is the server computer.
• The client computer then determines how to
  display this information to the user.

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Client-Side Computing

• In the past these programs are executed on the
  server computer. The client transmitted a
  request, and the server responded by executing a
  program and transmitting the result.
• Several performance problems occur
• There exists a delay between the moment when the
  client asks that a program be executed and the
  time the results are returned.
• Server programs often deal with many clients at
  once, reducing performance.

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Client-Side Computing

• In client-side computing, rather than executing
  the program on the server side and transmitting
  the result, the server will transmit the program
  to the client.
• The client will execute the program locally.
• Advantages
• Program run on a less heavily loaded system
• Only delay is the time to transmit the program
  user interactions take place locally.

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Bytecode Interpreter and Just In Time Compilers

• Client many not know what type of machine the
  server is using.
• The traditional concept of computer programs
  being translated into machine code for a specific
  machine will not work.
• Java is translated into a device-independent
  bytecode.
• This Bytecode is like a machine language for an
  imaginary machine, a Java-specific machine, or
  Java Virtual Machine (JVM)
• Each computer that runs Java programs then
  processes these bytecodes into a form that works
  correctly on the current system.

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Interpreters vs. JIT Compilers

• The easiest scheme is to have an interpreter that
  reads and executes bytecodes one by one.
• A better performance can be obtained by using a
  just-in-time (JIT) compiler.
• This system takes the Java bytecodes and
  translates them into the machine code native to
  the client system.
• These programs then run as fast as any compiled
  program created specifically for the client
  computer.

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Security Issues

• A program running on the client side could have
  full access to the client computer resources.
• There is potential for such a program to do
  significant damage, such as erasing files from a
  hard drive.
• Java programs use a security manager provided by
  the client.
• It limits the actions that can be performed by
  the Java program provided by the server.
• For example, no access to the file system or
  access to other machines across the Internet.

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Specialization of Interfaces

• The sequences of commands needed to perform
  graphical operations varies greatly from one
  machine to another.
• The solution to this problem requires a careful
  coordination between the client and server
  computers.
• Portions of a Java program originating on one
  machine, and other parts coming from the second.
• The server program is structured in terms of
  generic classes, such as Window and Button.

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• Generic classes are the same regardless of the
  type of system on which the Java program is run.
• When executed, these components create a peer
  component.
• The peer component originates on the client
  system and is not part of the server program.
• Thus, a button running on a PC will create a
  PC-Button peer, while the same program running on
  a Macintoch will create a Mac-Button peer.

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The White Paper Description

• Java is a simple, object-oriented, network-savvy,
  interpreted, robust, secure, architecture
  neutral, portable, high-performance,
  multithreaded, dynamic language.
• A buzzyword heavy description

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Java is Simple

• Simpler than C
• No preprocessor.
• Far fewer special cases.
• No confusing features such as overloaded
  operators, independent functions, global
  variables, goto statement, structures, or
  pointers.
• Augmented with a larger library of high-level
  development tools.

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A Remark on Pointers

• In many languages, there is a distinction between
  a value vs. a pointer to a value
• Values are static, fixed-size entities
• Pointers are dynamic quantities filled at
  run-time.
• There are important reasons why object-oriented
  language should make heavy use of pointers.
• Java does so, but implicitly. Everything is
  internally a pointer.
• Elimination of this construct removes common
  errors, making it easier to construct reliable
  and correct programs.

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Java is Object-Oriented

• Java has no functions and no variables that can
  exist outside of class boundaries.
• Thus, all Java programs must be built out of
  objects.
• C and Object Pascal (Delphi) combine OO
  features on top of an existing,
  non-object-oriented language.
• Programmers can continue working in old,
  non-object-oriented fashion.
• By forcing all programs into an object-oriented
  structure, benefits of OO are realized.
  (encapsulation, reusability)

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Java is Network Savvy

• The language provides a rich set of tools for
  programming across a network.
• The Java standard library provides classes for
  describing universal resource locators (URLs) and
  for execution in controlled environments such as
  a World Wide Web browser.

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Java is Interpreted

• Java was designed for a multicomputer execution
  environment.
• Any type of computer could be used as a Java
  virtual machine.
• Java programs were compiled into bytecodes ,
  could be stored on any type of machine. An
  interpreter would read the bytecodes and execute
  them.
• Interpreters are much slower in execution.
• A just-in-time (JIT) compiler is a system that
  read machine-independent bytecode and translates
  them into actual machine instructions.

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Java is Robust

• The Java language and associated libraries are
  designed to be graceful in the presence of
  hardware and software errors.
• The use of exception handling.
• Programmers are forced into thinking about
  potential source of errors.
• Java has an automatic memory management, garbage
  collection.
• It detects and recovers memory that is no longer
  being used by the current running program.

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Java is Secure

• Multi-level Security System
• First Level
• Eliminating pointers remove the most common
  errors.
• The Java language insists that array index values
  are cheked before the are referenced.
• All variables must be assigned values before
  being used.
• Second Level
• Bytecodes are checked for common errors.
• Such as they do not access classes incorrectly,
  overflow or underflow the operand stack, or use
  illegal data conversions
• Java programs are restricted in the type of
  operations they can perform.
• When they execute a program brought over the
  network, their local computers are safe from
  tampering.

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Java is Architecture Neutral

• Java bytecodes work with all machines.
• A Java program is the same whether it runs on a
  PC. a Macintosh, or a Unix system.
• C libraries differ from one platform to
  another.
• Thus, it is difficult to move programs designed
  for the PC onto a Macintosh.
• Java hides these application-specific details
  under a layer of abstraction in the standard Java
  library.

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Java is Portable

• Java programs are portable because the Java
  library hides architecture-specific concepts and
  bytecodes are the same for all machines.
• The exact same program can be compiled on one
  system, then executed on many different types of
  systems.

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Java is High-performance

• Just-in-time compilers allow platform-dependent
  Java programs to be executed with nearly the same
  run-time performance as conventional compiled
  languages.

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Java is Multithreaded

• Java is one of the first languages to be designed
  for multiple threads of execution running in one
  program.
• It is easy to set up multitasking.
• The coordination of these parallel processes is
  also relatively simple.

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Java is Dynamic

• Because Java programs move across the Internet
  and execute on the users local computer, they
  permit a degree of dynamic behaviors impossible
  in older style systems.