Lesson Objectives

• How did we get here?
• What exactly is Java?
• What is Java used for?
• What makes Java better?

Class Notes

How Did We Get Here?

• In the Beginning: Assembly, FORTRAN, COBOL
• Structured: C, Pascal, COBOL
• Object-Oriented: C++, Smalltalk, Ada?
• Database-Aware: PowerBuilder, Gupta
• Component-Based: Visual Basic, Delphi
• Network-Oriented: Java

What Exactly is Java?

• Programming Language Invented by Sun Microsystems
• Syntax is based on C++
  • "C++ without the pitfalls"
• Runs on all platforms
  • "Write once, run anywhere"
• Wide industry acceptance
  • IBM, Sun, Netscape, Oracle, Novell, Microsoft

What is Java used for?

• Applets
  • Embedded programs in web pages
• Applications
  • Stand-alone applications (no browser required)
• Servlets
  • Dynamic web page creation
• Distributed Applications
  • RMI: Remote Method Invocation, CORBA

What makes Java Better?

• Simple
• Object-Oriented
• Distributed
• Robust
• Architecture Neutral
• Multi-Threaded
• Vendor Neutral

Simple

• Features:
  • Automatic Memory Mgmt.
  • No pointers
  • No header files or pre-processor
  • No operator overloading
  • No multiple inheritance
• Benefits:
  • Easier to program
  • Easier to debug
  • Easier to maintain
  • Fewer latent bugs

Object-Oriented

• Features:
  • Inheritance
  • Encapsulation
  • Polymorphism
  • Component-Based (JavaBeans)
• Benefits:
  • Programs are more extensible
  • Programs are more maintainable
  • Components allow a division of labor between component makers and component users

Distributed

• Feature:
  • Network-oriented design
  • Remote Method Invocation (RMI)
• Benefit:
  • Easily move objects in an n-tier architecture

Robust

• Feature:
  • Strongly-typed
  • No poiner arithmetic
  • Bounds-checking on arrays
  • Exception handling (try/catch/finally)
  • Build-in security model ("sandbox")
• Benefit:
  • Programs are more reliable
  • Programs are easier to debug
  • Program bugs are less likely to bring the entire system down.

Architecture Neutral

• Feature:
  • Runs on PC, Mac, UNIX, Mainframe
  • Data types are machine-independent
• Benefit:
  • Use one language for all tiers on the application:
    • User Interface
    • Database
    • Business Logic
  • Easily move applications to the most cost-effective platform(s)

Multithreaded

• Feature:
  • Multi-threading support is built-in to the language
    • The "synchronized" keyword
• Benefit:
  • Easier to understand than third-party multi-threading tools or non-object-oriented API calls

Vendor Neutral

• Feature:
  • Not proprietary to a single company
• Benefit:
  • Not dependent on a single company for tools and support
  • Allows one to pick best-of-breed tools

Review Questions

1. What makes Java platform independent?
2. What features of Java make it a robust language?