CSCI 224 Introduction to Java Programming

Course Objectives  Learn the Java programming language: Syntax, Idioms Patterns, Styles  Become comfortable with OOP Learning to think in objects  Learn the essentials of the Java class library And how to learn about other parts when you need them

Writing Code  It is not enough to write code that works.  It is important to write code that is also Legible, Maintainable, Reusable, Fast and Efficient

Java  Sun defines Java as a: “…simple, object-oriented, network savvy, interpreted, robust, secure, architecture-neutral, portable, high- performance, multi-threaded, dynamic language.”

What is Java?  History of Java First started in 1990 as Sun’s Green project  Digitally controlled consumer devices identified as trend Trend did not grow as expected 1994 – WWW popularity Netscape packaged Java within browser  - MS Explorer followed suit Success ultimately depended on e-commerce

What is Java  Java is a high level,third generation programming language  Compared to other languages it is most similar to C and shares much of the syntax Unlike C++ Java is not a superset of C and substantial amounts of C code would need to be reworked to become a Java program

Java is :  A Platform  Simple  Object-Oriented  Platform independent  Safe  High Performance  Multi-Threaded  Garbage Collected

Platform  Three elements to Java The programing language The compiler The Java interpreter  The Java compiler creates byte code and not code native to particular platform. The result is that the JVM the runtime machine interprets this code on the fly and translates it to the machine.

Simple  Java is designed to be easy to write. Not a lot of special tricks to confuse beginners Memory allocation and deallocation are handled automatically. Syntax is straight forward in most situations.

Object Oriented  The core concept of Java Everything is an object. Huge libraries of objects are available.  Learning to use the API is essential

Platform independent  The Java byte code is never really executed on the host machine.  Each JRE / JVM does all the work of interfacing with the OS and machine.  Also eliminates having to deal with variations in platform architecture Integer is always four bytes.

Safe  Java was designed from the ground up to allow for execution across a network.  Applets – executed with set limitations on what they can do to within your system. Essentially they run in a sandbox.

High Performance  The Java byte code compiles on the fly with speeds that rival the C++ compiler.

Multi-Threaded  Java is inherently multi-threaded allowing a single program to execute different processes independently and continuously.  The is a cost to this for the programmer. Just as in C pointer arithmetic can be hard to debug, debugging threads is a challenge.

Garbage Collection  There is no need to explicitely allocate or de-allocate memory in Java.  No need to write destructor methods.  The JRE handles the trash.

Practical  What do you need to run Java. JDK – Java developer's Kit. JRE – Java Runtime Enviroment SDK – Java Software Development Kit  IDEs Several development tools exist.  The most basic thing you need is Notepad or any text editor to write the java source files. Jbuilder, Sun's One Studio, JCreator, Forte and Eclipse are just a few.

Development Tools  1995 – First JDK released by Sun (1.0) Very limited  JDK 1.1 released Limited GUI creation  1.2 released Major change – Swing components Java 2 SDK release 1.2 Better known as Java 2  Most current version: 1.5

Development Tools  Java 2 Editions Java 2 Platform, Standard Edition Java 2 Platform, Enterprise Edition Java 2 Platform, Micro Edition

Java Programs  Applets Java program running within client Web browser  Servlet Java program running on a server Can ‘cooperate’ with applet or application  Application Standalone program