Background - Introduction to Programming in Java - Lecture Slides, Slides of Java Programming

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• Objectives
  • give a non-technical overview of Java

1. Background

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Contents

1. Java, etc.
2. Java's Advantages
3. Java's Disadvantages
4. Some History
5. Types of Java Code
6. Java Safety
7. Core Libraries
8. Notes on Java Installation

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Other Javas (e.g. OpenJDK)

• I'll be using the Java developed by Oracle

(initially by Sun).

• There are other implementations of Java, the

most important being OpenJDK

• popular on Linux
• It's easier for non-Oracle people to add

features to OpenJDK.

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2. Java’s Advantages

• Productivity
  • object orientation
  • many standard libraries (packages)
• Simpler/safer than C, C++
  • no pointer arithmetic, has automatic garbage collection, has array bounds checking, etc.

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• Network support
  • communication with other machines/apps
  • variety and standards:
    • sockets, RMI, IPv
  • security, resource protection
• Multithreading / concurrency
  • can run several ‘threads’ at once
  • extensive concurrency libraries

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• Portablility / Platform Independence
  • “write once; run anywhere”
  • only one set of libraries to learn
• Supports native code
  • can integrate legacy (old) C/C++ code
• JDK is free

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Some Java Statistics (May 2012)

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3. Java’s Disadvantages

• Java/JDK is still being developed
  • many changes between versions
• Sun has not guaranteed backward

compatibility of future versions of Java.

• at the moment, when old-style code is compiled, the compiler gives a “deprecation” warning , but will still accept it

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• Cross-platform testing and debugging has

been a problem (due to inconsistencies)

• most major problems have been fixed
• “Write once; run anywhere” means that

some local OS features weren't supported:

• e.g. right button actions under Windows
• no joysticks, special keypads
• this is fixed in the latest versions of Java

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• Java’s security restrictions makes some

code hard to write:

• cannot “see” much of a local machine
• newer JDK versions make this easier
• The existing code base (in C, VB, etc.)

means that people do not want to rewrite

applications in Java.

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• Slow Internet connections
  • makes it difficult (and irritating) to download medium/large size applets
  • e.g. flash files have replaced Java animations
• Lots to learn
  • Java language (small) and Java libraries (very, very large)

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• There seem to be few ‘serious’ Java

applications. But ...

• the Java compiler (javac) is written in Java
• most custom Java applications are internal to a company - they don’t have the high profile of major vendor software

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• August 1993: the project was cancelled

after two commercial deals fell through.

• The Web became popular during 1993.
• July 1994: Sun restarted work on Java as a

Web programming language

• Java contains networking features, platform portability, and a small runtime system

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• Java released May 1995
  • Netscape supported Java in Navigator 2.0, which gave it an enormous boost
• May 1996: JDK 1.0 released
  • hurried library development; mistakes made
• February 1997: JDK 1.1 released
  • major changes in the event model used by the GUI; inner classes introduced continued Docsity.com