The Java Story

The Java Story

• 1.
  Chapter 1 The JavaStory Foundational Java Key Elements and Practical Programming
• 2.
  Foundational Java • Thesematerials come from Chapter 1 of ‘Foundational Java’ by David Parsons – Springer, London, 2012 – ISBN (Print) : 978-1-4471-2478-8 – ISBN (Online) : 978-1-4471-2479-5
• 3.
  Java • Major globalprogramming language – desk top, web and enterprise systems – embedded in mobile phones, Blu-ray players etc. • ‘virtual machine’ supports a family of related languages – Scala, Groovy, versions of Ruby and Python • Came to wide attention via the web in 1995 – Popularity riding on the explosion of interest in the Internet and World Wide Web in the mid 1990s
• 4.
  A Brief Historyof Java • Started as Sun Microsystems prject to build the ‘Star7’ Personal Digital Assistant (PDA) – Intended to control all the electronic devices in the home – Needed to work on various pieces of hardware, from televisions to toasters • The Star7 language was called ‘Oak’ – Later changed to Java for trademark reasons • Moved onto the web with the ‘HotJava’ browser – able to run small Java programs (known as ‘applets’) within its window • Java has since matured into one of the key technologies of global software development
• 5.
  Characteristics of Java •simple • object-oriented • distributed • robust • secure • architecture neutral • portable • high performance • multithreaded • dynamic
• 6.
  Simple • ‘C++ withoutthe knives, guns and clubs’. • One major simplification in Java is the way that memory is managed, using largely automatic processes rather than requiring the programmer to do this
• 7.
  Object-oriented • Object-oriented languageshave become common since the 1990s • Data and processes are ‘encapsulated’ together to provide objects that have both state (data) and behaviour (processes) • Easier to model the behaviour of the real- world things that we are trying to reflect in software
• 8.
  Distributed • Trend towardsmaking the machine on the desk less important then the network it is connected to • Java is designed for network programming: – Common Internet protocols • HTTP (Hyper Text Transfer Protocol) • FTP (File Transfer Protocol) – Socket communication – Remote method invocation (RMI) – Web services
• 9.
  Robust • Does notbehave unpredictably or fail due to programmer error • Removes the risks of memory pointers from code: – Manipulating memory that has not been correctly allocated can crash a program – Failing to free up memory that has been finished with leads to ‘memory leaks’ where a program can eventually run out of memory • Java has only ‘references’ to objects, not pointers • Garbage collector automatically recovers memory from objects that are no longer needed
• 10.
  Secure • Security systemsbuilt into Java ensure that the code, once written, is not easy to tamper with • Restrictions placed on what Java applets can do when they are running inside browser
• 11.
  Architecture Neutral • ‘writeonce, run anywhere’ • Combines a compiler and an interpreter • The Java compiler does not convert the source code into an executable for a specific environment – it compiles into ‘byte code’ • Byte code can be run on a Java Virtual Machine (JVM), software that interprets the byte code to run on a specific computer • The same byte code can run on different systems • Each platform needs to have its own virtual machine
• 12.
  The Java VirtualMachine • The Java virtual machine (JVM) allows the same byte code to be run on different platforms and operating systems. Java source code Java compiler Java byte code Java virtual machine Java virtual machine Java virtual machine
• 13.
  Portable • Architecture neutrality •Portable definitions of data types – e.g. all ‘int’ data types are thirty-two bits long • Java types are also always signed – can contain both positive and negative numbers – no ‘unsigned’ types
• 14.
  High performance • Just-in-time(JIT) compilers speed up the interpretation process • Native compilers • Java chips – embedded in electronic devices • HotSpot compiler optimises code while it is running
• 15.
  Multithreaded • Java makesit easier for programmers to write multithreaded programs that are more efficient than single threaded programs (where only one thing can be happening at any one time) • Even where the operating system itself is not multithreaded, Java code can be written that uses multiple threads of control
• 16.
  Dynamic • Java candynamically change the resources it is using at run time • Useful in a distributed environment – programs can be flexible in terms of size and behaviour • Easy to locate objects at run time, even when they are in different places
• 17.
  The JDK andthe JRE • Java installations come in two forms • Java Software Development Kit (JDK) – for writing Java programs – includes the Java compiler (javac) • Java Runtime Environment (JRE) – includes the Java Virtual Machine and supporting libraries for running Java code – no compiler or other development tools • A Java Integrated Development Environment (IDE) may include the necessary tools
• 18.
  Java Versions Version YearHighlights 1.0 1995 First public version 1.1 1996 Event handling mechanism for user interfaces 1.2 (Java 2 platform) 1998 Collections Framework, Swing GUI libraries. Java split into three editions 1.3 2000 Updates to existing features, including better sound support 1.4 2002 Performance and security improvements, XML processing, new input/output libraries 5.0 (change in version style) 2004 Generics, annotations, autoboxing, features similar to C# 6 2007 Web services, Java to XML Binding. Update 10 made major changes to JRE footprint. 7 2011 Improvements to several areas including security, and better support for RIAs and dynamic languages
• 19.
  Major Milestones • Javabecame open source in 2006 • Sun Microsystems was acquired by Oracle Corporation in 2010
• 20.
  Java APIs • CoreJava syntax (keywords and fundamental libraries) + Java application programming interfaces (APIs). • Some of the more specialised libraries (often known as the Java extensions) are not provided with the standard edition of the JDK • Java Standard Edition, (Java SE) – Desktop applications, all the core libraries • Java Enterprise Edition (Java EE) – client server programming • Java Micro Edition (Java ME) – small or embedded devices
• 21.
  Learning Java • Toprogram in Java successfully we need to understand object-oriented concepts • Java has a rich syntax and wide ranging APIs • It can be used for all kinds of programming, from writing a command line utility to building a distributed client server system or a complex multithreaded real-time system • Continues to evolve and provides programmers with the tools for coding a host of applications in all kinds of contexts
• 22.
  Some Questions… • What'sthe difference between the JDK and the JRE? • What is byte code? • If Java is cross platform, why do I have to download different versions of it for Windows, Mac, Linux etc? • Why is Java popular as a programming language?
• 23.
  For More Information… •See the Foundational Java page on the Springer web site – http://link.springer.com/book/10.1007/978-1- 4471-2479-5/page/1 • Download code and other support materials from ‘introjava.com’ – http://www.introjava.com/