COMP201 Java Programming

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COMP201 Java Programming
Topic 1 Introduction Readings Chapter 1
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Outline

• C, C, and Java
• How Java is related to C and C
• Advantages of Java
• Writing good codes in Java is easier than in C or
  C
• Java libraries (packages)
• Where the power of Java come from
• Java and the internet
• What Java is good for
• Course content

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C, C, and Java

• C designed in 1970s for operating system
  programming, i.e. UNIX
• High-level language compared with assembly
  language
• Low-level compared with C or java
• Low level Easy manipulation of hardware
• High level Relying on lower level software to
  implement task with minimum amount of code.
• Strengths
• Not restrictive, especially in relation to type
  conversion.
• More efficient than C and Java.
• Weaknesses
• Not object-oriented does not support abstraction
  and encapsulation
• Difficult to manage in large projects.
• Little built-in functionalities. Programmer need
  to start from scratch.
• Easy to make mistakes. (pointers, ab vs ab)

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C, C, and Java

• C designed in 1980s, complete superset of C
• Changes
• Support for Object-Oriented programming
• Strengths
• Improved data abstraction and encapsulation
• Makes it easier to manage large projects
• More extensive built-ins (standard libraries)
• Weakness
• Considered by many to be over-complicated
• Contains all of Cs problems

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C, C, and Java

• C designed in 1980s, complete superset of C
• Changes
• Support for Object-Oriented programming
• Strengths
• Improved data abstraction and encapsulation
• Makes it easier to manage large projects
• More extensive built-ins (standard libraries)
• Weakness
• Considered by many to be over-complicated
• Contains all of Cs problems

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A Short History of Java

• 1991, Green Project, A group of engineers from
  Sun, led by Patrick Naughton, Sun Fellow, James,
  Gosling wanted to design a small consumer devices
  computer language, which has to be small, tight,
  platform-neutral, secure. So burn Java.
• 1992, 7 intelligent remote control (no
  buyer).
• 1993-1994 Green project tried to sell the
  technology, but no buyer.
• Mean while WWW was growing. In 1994 most people
  were using Mosaic create by Marc Andreessen.
• In 1994, created HotJava with Java.
• 1995, demo HotJava at Sun World inspired the Java
  crazy
• 1996 Sun released Java 1.0, but it is not for
  serious application.
• 1998, released Java1.2 Standard SDK with a solid
  graphic toolkits.
• Version 1.3, 1.4 are incremental improvements
  over the initial release.
• 2004, released version 5.0 that updated the Java
  language in significant way.

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C, C and Java

• Java a language of 1990s
• The design of Java starts with C syntax and
  semantics
• Adds a few features from C Objects, exceptions
• Leaves out parts unneeded, unsafe, complex (not
  backward compatible)
• Gosling Java omits many rarely used, poorly
  understood, confusing features of C that in our
  experience bring more grief than benefits.
• Adds a few facilities not present in C or C
• Garbage collection, concurrency, runtime error
  checking, object serialization, interface, inner
  classes, threads
• Strengthens portability and security

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C, C and Java
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Outline

• C, C, and Java
• How Java is related to C and C
• Advantages of Java
• Writing good codes in Java is easier than in C or
  C
• Java libraries (packages)
• Where the power of Java come from
• Java and the internet
• What Java is good for
• Course content

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Advantages of Java

• According to Suns Java White paper
• Java is a simple, objected-oriented,
  distributed, interpreted, robust, secure,
  architecture-neutral, portable, high-performance,
  multi-threaded, and dynamic language.
• Most of the claims are justified, while others
  are controversial.

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Advantages of Java/Simple

• Streamlined C language
• No typedef, union, goto, comma operator
• No header files
• C list.h, list.c
• Java List.java
• No makefile
• Java compiler can figure out dependencies among
  classes

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Advantages of Java/Simple

• Fixed problematic areas
• No pointers, no function pointers
• Add garbage collection. Memory leaks no more
• No code like this
• if ( Head NULL )
• Head(NODESET ) memAllocate(sizeof(NODESET))
  
• (Head5) tmpNode
• (Head)-gtnext(Head)-gtprevNULL
• memDeallocate( Head )
• Eliminated the possibility of confusing an
  assignment with a test for equality in a
  conditional statement.
• if (ab) does not compile

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Advantages of Java/Simple

• Everything is a class except several primitive
  types
• Array is a class. Cannot go over bound.
• No this
• int a5 a50
• However, Java libraries are quite complicated

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Advantages of Java/Object-Oriented

• More so than C.
• Combine data and behavior into one unit, the
  object
• Programs are collections of interacting,
  cooperating objects
• Advantages of OOP
• Provide strong data abstraction and encapsulation
• Gives framework for design
• Allows independent development and testing
• Facilitates system extensions and maintenance
• More opportunity for code re-use

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Advantages of Java/Platform-Independent

• C and C programs are compiled into object code,
  
• Object code is directly processed by hardware
  processor.
• Require a separate compiler for each computer
  platform, i.e. for each computer operating system
  and the hardware set of instructions that it is
  built on.
• Java programs are compiled into bytecode
• Bytecode is processed by a program called java
  virtual machine (JVM), rather than by the "real"
  computer machine, the hardware processor.
• Platform differences dealt with by JVM
• Consequently, Java programs can run on any
  platform. Write once, run anywhere.

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Java Virtual Machine
Runtime environment (Java Platform)
Compile time environment
Class loader bytecode to verifier
Java Libraries
Java Source
Java Virtual Machine
Bytecodes move locally or through net
HotSpot Compiler
Java Compiler
Runtime System
Operating System
Java bytecode (class)
Hardware
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Advantages of Java/Distributed and Multithreaded

• Networking capabilities of Java is both strong
  and easy to use.
• It is easy to do multithreading in Java. Threads
  in Java can even take the advantage of
  multiprocessor system.

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Advantages of Java/Robust and Secure

• Fewer language loopholes
• No pointers, typecasts limited. (Easier to
  produce error free source code)
• Compilers are strict
• Require initialization of variables, enforces
  type consistency, requires
• prototypes (Less chance of error in compiled
  code)
• Runtime error checking
• Array bounds, null reference access (Less chance
  of runtime error)
• Security manager
• System to control permissions for high-level
  actions
• Runtime verifier checks untrusted bytecode
• Avoids havoc from hand-constructed bytecode

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Advantages of Java

• In Summary, writing good/bug-free codes in Java
  is easier than in C or C
• javadoc generates documentation automatically
• Very useful
• Example HLCM

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Outline

• C, C, and Java
• How Java is related to C and C
• Advantages of Java
• Writing good codes in Java is easier than in C or
  C
• Java libraries (packages)
• Where the power of Java come from
• Java and the internet
• What Java is good for
• Course content

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Java Libraries

• Java has far expanded traditional scope of a
  languages libraries
• Java 2 SDK 5.0
• 3,270 classes and interfaces
• 32,138 methods
• Much less effort required to accomplish common
  tasks
• Platform-specific details are handled
• All programs improved when common core updated

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Java Libraries

• Collection of classes grouped into packages
• Java equivalent of C libraries
• java.lang
• String, Math, Exception, Thread, Runtime, etc
• java.util
• Vector, Stack, hashtable, Date, Tokenizer
• java.io
• Varieties of input/output processing
• java.net
• Networking, client/server sockets, URLs
• java.awt, javax.swing
• Windows, buttons, drawing, images, events

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Java Libraries

• java.security
• Encryption, digital signature, message digest
• java.text
• Formatting and parsing
• java.sql
• Database connectivity
• java.rmi
• Remote method invocation, distributed objects
• The list goes on
• And it is continuing to expand. Java is still
  young

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Outline

• C, C, and Java
• How Java is related to C and C
• Advantages of Java
• Writing good codes in Java is easier than in C or
  C
• Java libraries (packages)
• Where the power of Java come from
• Java and the internet
• What Java is good for
• Course content

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Java and the Internet

• Java is intended to be used in networked/distribut
  ed environments.
• Increasingly used for middleware to communicate
  between clients and servers, acting as a
  universal glue that connect user with information
  from various sources. Example JMOL
• Made possible by portability and multithreading
  and networking capabilities.

JDBC
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Course Contents

• Language Basics
• Classes, objects, inheritance, interface, inner
  classes, exception, I/O stream
• Components in the following diagram
• Other issues
• Multithreading, network, Applet, security

Applet
Client Browser
Server
Java Networking
Applet Swing (GUI)
Servlet
Remote Method Invocation
JDBC
DB
User