oop

• Object-Oriented Programming (OOP)


  Programming paradigm that focuses on modeling data
• Programming language families

  • Machine languages
  • Assembly languages
  • High-Level languages
• Machine languages


  • Comprised of 1s and 0s
  • The "native" language of a computer
  • Difficult to program - one misplaced 1 or 0 will cause the program to fail
• Machine language code


  • 1110100010101
  • 111010101110
  • 10111010110100
  • 10100011110111
• Assembly languages


  • A step towards easier programming
  • Comprised of a set of elemental commands which are tiled to a specific processor
  • Assembly language code needs to be translated to machine language before the computer processes it
• Assembly language code


  • ADD 1001010,1011010
  • MOV AX,BX
• High-Level languages


  • Represent a giant leap towards easier programming
  • The syntax of HL languages is similar to English
• High-Level language groups

  • Function-Oriented languages
  • Object-Oriented languages (OOP)
• Function-Oriented (Procedural) languages


  • Early high-level languages
  • Characterized by sequential sets of linear commands
  • The focus is on structure
• Object-Oriented languages


  • Most are high-level languages
  • The focus is on modeling data
  • Programmers code using "blueprints" of data models called classes
• Object-Oriented languages

  • C++
  • Visual Basic.NET
  • Java
• Java


  Programming language originally developed by Sun Microsystems, initiated by James Gosling and released in 1995
• Java

  • Object Oriented
  • Platform Independent
  • Simple
  • Secure
  • Architecture-neutral
  • Portable
  • Robust
  • Multithreaded
  • Interpreted
  • High Performance
  • Distributed
  • Dynamic
• James Gosling initiated Java language project


  June 1991
• Sun released the first public implementation as Java 1.0


  1995
• Sun released much of Java as free and open source software

  13 November, 2006
• Sun finished the process, making all of Java's core code free and opensource

  8 May, 2007
• Five Phases of JAVA Programs

  1. Edit

  2. Compile javac (java compiler)

  3. Load

  4. Verify

  5. Execute
• Tools You Will Need for Java Programming
• Popular Java Editors

  • Notepad
  • Textpad
  • Wordpad
  • Netbeans
  • Eclipse
  • JCreator
• Object


  Unique programming entity that has methods, has attributes and can react to events
• Method


  Things which an object can do; the "verbs" of objects
• Attribute


  Things which describe an object; the "adjectives" of objects
• Events


  Forces external to an object to which that object can react
• Class


  Provides a way to create new objects based on a "meta-definition" of an object
• Constructors


  Special methods used to create new instances of a class
• Class Names


  For all class names the first letter should be in Upper Case. If several words are used to form a name of the class, each inner word's first letter should be in Upper Case.
• Method Names


  All method names should start with a Lower Case letter. If several words are used to form the name of the method, then each inner word's first letter should be in Upper Case.
• Program File Name


  Name of the program file should exactly match the class name. When saving the file, you should save it using the class name and append '.java' to the end of the name.
• public static void main(String args[])


  Java program processing starts from the main() method which is a mandatory part of every Java program.
• Java Identifiers


  All identifiers should begin with a letter (A to Z or a to z), currency character ($) or an underscore (_). After the first character, identifiers can have any combination of characters. A key word cannot be used as an identifier. Identifiers are case sensitive.
• Examples of legal identifiers


  • age
  • $salary
  • _value
  • __1_value
• Examples of illegal identifiers


  • 123abc
  • -salary
• Robust: Java makes an effort to eliminate error prone

  situations by emphasizing mainly on compile time error

  checking and runtime checking.
• Multithreaded: With Java's multithreaded feature it is

  possible to write programs that can perform many tasks

  simultaneously. This design feature allows the

  developers to construct interactive applications that can

  run smoothly.
• Interpreted: Java byte code is translated on the fly to

  native machine instructions and is not stored anywhere.

  The development process is more rapid and analytical

  since the linking is an incremental and light-weight

  process.
• High Performance: With the use of Just-In-Time

  compilers, Java enables high performance.
• Distributed: Java is designed for the distributed

  environment of the internet.
• Dynamic: Java is considered to be more dynamic than C

  or C++ since it is designed to adapt to an evolving

  environment. Java programs can carry extensive amount

  of run-time information that can be used to verify and

  resolve accesses to objects on run-time.
• Edit

  The programmer writes the program (preferably on a

  notepad) and saves it as a ‘.java’ file, which is then

  further used for compilation, by the compiler.