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Given by Nancy J. McCracken,Geoffrey C. Fox at Peking Tutorial, Web Certificate on Spring-Summer 1997. Foils prepared 18 May 97
Outside Index
Summary of Material
| Overview including History and alpha versus production issues |
| Comparison of Java and Javascript |
| Overall Java Philosophy and Features including security etc. |
And in Remaining Parts of Tutorial!!
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Denote Foils where Image Critical
Denote Foils where HTML is sufficient
Java Tutorial - May 1997
Abstract of Java Tutorial
Overview and History of Java Development
What are Java and HotJava in a NutShell?
HotJava Story 1994-1996
HotJava Alpha Capabilities
HotJava's Future 1996- ?
Overview -- Java and the World Wide Web
Overview -- What are Java applets in detail?
Running a Java Applet
History of Java Language and Team
History of Java Language and Team (contd)
JDK 1.0 -- The Real Java Development Kit!
Java Beta --> 1.0 Books -- I
Java Beta --> 1.0 Books -- II
Java Beta --> 1.0 Books -- III
Java vs. JavaScript
Comparison of Java and JavaScript -- I
Comparison of Java and JavaScript -- II
Overall Java Philosophy and Features
Some Key Java Features
Java Features -- It's Simple and Familiar!
Java Features -- It's Object-oriented
Java Features -- It's Architecture-Neutral
Java Features -- It's Portable
Java Features -- It's Somewhat Interpreted
Java Features -- It's Distributed
Java Features -- It's Robust
Java Features -- It's (Hopefully) Secure
Java Features -- High Performance
Java Features -- It's Multithreaded
Java Features -- It's Dynamic
Java 1.1 Features
Outside Index
Summary of Material
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| Instructors: Geoffrey Fox |
| Nancy McCracken |
| Syracuse University |
| 111 College Place |
| Syracuse |
| New York 13244-4100 |
HTML version of Basic Foils prepared 18 May 97
Full HTML Index
| Overview including History and alpha versus production issues |
| Comparison of Java and Javascript |
| Overall Java Philosophy and Features including security etc. |
| Java Programming Language |
| Object Oriented and Class Structure |
| Exceptions |
| Applet Programming and Threads |
| Abstract Windowing Toolkit |
| Networking and I/O |
| Futures and HPCC Implications |
HTML version of Basic Foils prepared 18 May 97
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HTML version of Basic Foils prepared 18 May 97
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What is Java?
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What is HotJava?
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HotJava alpha3 (1994-5)
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HotJava 1.0 (1996)
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Alpha release of Java/Hotjava included:
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| In Short, Alpha Java/HotJava was a complete software release of all system components, free for research and subject to ($125K) licence for business use. |
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HotJava toolkit (1996-): class libraries for building web-aware applications i.e. The "Browser" class
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| Natural Use of HotJava is for applications where it is critical to customize User Interface to a greater degree than Netscape allows |
| Netscape hopes you will use JavaScript to customize a core browser supplied by Netscape |
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| Browsers (HotJava, Netscape 2.0/3.0 ..) supporting Java allow arbitrarily sophisticated dynamic multimedia applications inserts called Applets, written in Java, to be embedded in the regular HTML pages and activated on each exposure of a given page. |
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Applet constructs are implemented in terms of a
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Steps to running a Java Applet:
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Using a Browser
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Using appletviewer
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| Starts in 1991 by Project Green --- a group in Sun that detaches from the main campus as a semi-autonomous task force focused on operating software for consumer electronic devices such as smart set-top boxes |
| Gosling (creator of Sun NeWS which had major conceptual impact both on current Java and Telescript models) realizes that C++ is not adequate and initiates development of a new language Oak, later renamed as Java. |
| A PDA (Personal Digital Assistant -- codename *7) based on Oak/Java ready in 1993. Green Team incorporates as FirstPerson, Inc. |
| *7 proposal to Time-Warner rejected in 1993. 3DO deal falls through in 1994. FirstPerson, Inc. dissolves. |
| Small group (~30 people, now Java Team) continues development and decides to adapt Oak as a Web technology. |
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| An experimental web browser written in Java, called WebRunner and later renamed as HotJava, ready in 1994. |
| Java/HotJava published in April '95. |
| Netscape licences Java in May '95 and builds Java into Netscape 2.0 -- This confuses ownership and open-ness of Java |
| Beta JDK (Java Development Kit) published in summer/fall '95. It is better software but lower functionality than Alpha. |
| First alpha Java books appear in fall '95 such as a popular overview by SAMS and technical book "Java!" by Tim Ritchey, edited by New Riders. |
| Dec 4 1995 Business Week cover story on "Software Revolution --- The Web Changes Everything" exposes Java as a breakthrough force in the expanding Web/Internet. Also points out that "Java as a business" is yet to be defined. |
| In next week, SGI IBM Adobe Macromedia and finally Microsoft adopt/license Java. It appears that Java will be open and should be adopted by open Web community |
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| Version 1.0 of JDK released January 96 by JavaSoft |
1.0 JDK should be the Internet standard and so compatible with ongoing Java implementations by all licensees, most notably Netscape. Beta/1.0 JDK includes:
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| Java 1.1 in Spring 97 has yet more improvements |
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| Hooked on Java, by Java developers Arthur van Hoff, Sami Shaio, Orca Starbuck, Addison-Wesley, is the (first) serious (but still rather high-level) book on beta Java. It contains example applets, but not much on programming. |
| Teach Yourself Java in 21 Days, by Laura Lemay and Charles L. Perkins, Sams.net Publishing, is a "how-to" book at the intermediate programming level. It concentrates on applets and windowing more than the object-oriented part of the language. |
| Java in a Nutshell, by David Flanagan, is the language reference book in the familiar O'Reilly series. |
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The Java Programming Language, by Ken Arnold and James Gosling, Addison-Wesley, May 1996, has lots of details on the language basics for intermediate and advanced programmers. It covers threads and i/o packages, but not applets or windowing packages.
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| Java Primer Plus, supercharging Web applications with the Java programming language, by Paul M. Tyma, Gabriel Torok, and Troy Downing, Sams.net, doesn't assume a lot of programming background, has chatty explanations and still covers lots of programming detail. |
| Java, How to Program, by Deitel and Deitel, Prentice-Hall, starts with beginning programming concepts and progresses rapidly through Java language. It has the most programming exercises. |
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There are five books in the Java Series from SunSoft Press, Prentice-Hall.
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| * this title is great, but what happened to "express Java", "Percolating through Java", and "Java for Drips"? |
HTML version of Basic Foils prepared 18 May 97
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HTML version of Basic Foils prepared 18 May 97
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| Netscape renames Livescript as Javascript and this is an interesting variant of Java which is fully interpreted (code can be included directly in HTML file)-- use for overall customization of client |
| Use Java for detailed programming and JavaScript for overall integration of client interface and system |
| JavaScript: Interpreted by client and NOT compiled |
Java: Compiled on Server before execution on client
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| JavaScript: Object based -- no classes or inheritance -- built in extensible objects |
| Java: Object-oriented. Programs consist of object classes with inheritance |
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| JavaScript: Integrated with HTML as embedded ascii but of course HTML looks rather irrelevant at times! |
| Java: Applets distinct from HTML but invoked from HTML Pages |
| JavaScript: do not declare variables' datatypes -- Loose typing |
| Java: MUST declare variables' datatypes -- Strong typing |
| JavaScript -- Dynamic Binding -- object references computed at runtime |
| Java -- Static Binding -- object references must exist at compile time |
| Java and JavaScript are secure and cannot write to disk |
| JavaScript has most user interface features of Java (such as buttons and frames), except not mouse interactions like "drag and drop". |
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| Document The Java: A White Paper by Sun Microsystems -- October 1995 draft by James Gosling and Henry McGilton -- enumerates the following main features of Java: |
| Simple and Familiar |
| Object-oriented |
| Architecture-neutral |
| Portable |
| Somewhat Interpreted |
| Distributed |
| Robust |
| Secure |
| High performance |
| Multi Threaded |
| Dynamic |
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| Java omits several rarely used, poorly understood and confusing features of C++ including operator overloading, multiple inheritance, pointers and automatic type coercions. |
It adds automatic garbage collection which makes dynamic programming easier in Java than in C or C++.
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| It also adds 'Interface' construct, similar to Objective C concept, which often compensates for the lack of multiple inheritance by allowing method calling syntax to be "inherited". |
| The resulting language is familiar as it looks like C++ but is simpler and hence easier to program in. |
| It also results in a much smaller kernel which is suitable for planned Java ports to consumer electronic devices. Base (alpha) interpreter is ~40Kb, libraries and threads add additional 175Kb. |
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| Java model can be viewed as a C++ subset, with some dynamic elements inherited from Objective-C (method overloading, garbage collection). |
| Structures, Unions and Functions are absorbed into data and methods of Java classes -- Java is Simple! |
| The strength of Java object-oriented model is not is sophistication but in simplicity and the extensive class library associated with the system (some 250 public classes were released in both alpha and beta). |
| Java class plays also a role of a communication atom in the Web embedding model. Applet classes identify themselves by names in the HTML applet tag. Applet downloads other classes, present in the applet source. Hence, the Java class names play the role of addressing mode for the distributed Java code database. |
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| C/C++ programming in a heterogeneous network environment requires use and compatibility across several vendor platforms and the corresponding compilers. This problem is solved in Java by designing platform-independent binary representation called Java bytecode (or opcode). |
| Java compiler (written in Java and platform-independent) reads Java source and generates Java bytecode. These bytecodes are shipped to client machines upon browser requests. |
| Each client machine must run Java interpreter which performs runtime execution of Java bytecodes. Java interpreter is written in POSIX compliant ANSI C and needs to be ported to and conventionally compiled (once) on each individual platform. |
| Once the interpreter is ported, application developers don't need to worry at all about platform specificity and differences between native compilers. |
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| Java language offers a uniform abstract (virtual) machine model which is identical for all platforms. |
| SUN owns the Java Virtual Machine (see online report) -- it is universal while classes can be added by any user |
Unlike in C/C++ where various integers match the architecture of a physical machine at hand, Java byte, char short, int and long are always of the same size, equal to 8, 16, 16(unicode), 32 and 64 bits, respectively.
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| Differences between vendor specific windowing environments (X Windows, MS Windows, Macintosh) are removed in terms of the Abstract Windowing Toolkit (AWT) metaphor. |
| AWT is given by ~60 Java classes (alpha) which offer a universal GUI programming model, portable between UNIX, PC and Mac, and translated automatically to native windowing systems on individual platforms by Java interpreters. |
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| Java represents a compromise between fully compiled (like C/C++) and fully interpreted (like Smalltalk or Perl) models. |
| Java "compiler" produces a binary bytecode output which is portable and much smaller than the real binary for a specific machine (Typical bytecode size is of order of the original source code, within a factor of 2). |
| Java "interpreter" executes this bytecode and is therefore less dynamic than e.g. Perl interpreter (which performs an equivalent bytecode construction internally and on-the-fly when reading the program source). |
| In general, the compilation process is: a) time consuming and b) platform specific. Hence, interpreters are built and used to facilitate a) rapid prototyping and/or b) portability. Java model is focused on platform independence but the development throughput is also reasonable since the Java compiler is fast and generates compact bytecode output. |
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| Popular TCP/IP based protocols such as FTP or HTTP are supported in terms of network protocol classes. This facilitates various forms of distributed processing. New protocols (e.g. PVM etc.) can added and dynamically installed. |
| Distributed computing model of Java is mainly client-server, with Java compiler preparing the opcodes at the server side, and Java interpreter executing it at the client side. |
| One can expect more dynamic uses of Java with Java threads on both Server and Client side communicating with each other. This is illustrated by Java based Collaboratory developed by Vishal Mehra as NPAC/Ece Master's Thesis |
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| Java enforces compiler-time type checking and eliminates this way some error prone constructs of C/C++. |
| Pointer arithmetic is fully eliminated which allows e.g. for runtime checking of array subscripts and enforces security of the Java model. |
| Explicit declarations are always required, i.e. C-style implicit declarations are abandoned. This allows the Java complier to perform early error detection. |
| Rapid prototyping in Java is less natural than in JavaScript,Lisp, Tcl, Smalltalk or Perl, but the software quality assurance of Java is higher than in these more dynamic and 'forgiving' languages. |
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Java bytecodes are shipped across the network and executed on client machines. Security is therefore a critical issue and strongly enforced in Java.
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| Modifications of the C++ model such as eliminating pointer arithmetic and coercion were dictated mainly by the security requirements. |
| Most viruses are based on acquiring access to private/protected sectors of computer memory which is impossible in Java. |
| Java opcodes are executed at the client side by Java interpreter which operates exclusively on the virtual memory. Hence, unless there are security bugs in the Java interpreter itself, the model is safe and users cannot create security holes by incorrectly or maliciously written applets. |
| The bytecodes sent across network are verified at the client which prevents evil/corrupted classes from causing problems |
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| Java interpreter performs on-the-fly runtime execution of the Java bytecodes which can result in a satisfactory performance. |
| There are 3 ways of executing Java |
| Interpreter through a Browser -- Java approximately 50 times slower than C |
"Just-in-time" (JIT) Interpreter on a browser -- Java approximately 4 times slower than C
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Compiler for generating native machine code out of Java or Java bytecodes, viewed as intermediate compiler form
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| Java model offers preemptive multithreading, implemented in terms of the Thread class. Thread methods offer a set of synchronization primitives based on monitor and conditional variable paradigm by C.A.R. Hoare. Java threads inherit some features from the pioneering Cedar/Mesa System by Xerox Park that gave birth to Macintosh and object-oriented programming. |
| A typical use of Java multithreading in applet programming is to have several independent but related simulations (e.g. various sorting algorithms), running concurrently in an applet window. Multithreading is also used internally by the browser to handle multiple document dynamics. |
| Another interesting application domain are multi-HotJava environments to come such as collaboratory or gaming. |
| Java threads don't have built-in point-to-point communication primitives. Various thread communication environments can be provided by coupling the thread and network protocol objects. |
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| Java model is more dynamic than C++ and closer to Smalltalk or Perl. |
| Subclasses don't need to to be recompiled after superclass implementation is updated. |
| C++ has "fragile superclass" problem where must recompile children if change anything (method/instance variable) in a superclass or referenced class -- Java resolves references at runtime and avoids this. |
| Classes have runtime representation (implemented in terms of the Class class) which allows one to look up type of a given object instance at runtime (in C cannot know if pointer is to integer or browser!) |
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| Several new capabilities in the area of abstract windowing toolkit improvement and new model for event handling |
| Has the "Java Database Connectivity" (JDBC) built in allowing access to general databases |
| Improved Security |
| RMI or remote method invocation supports standard client server interactions |
| Allows objects to be transmitted in a standard way (object serialization) |