Introduction to Java

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Introduction toJava
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Java Characteristics

• Simple (relatively)
• Object-Oriented
• Distributed
• Interpreted
• Robust and Reliable
• Secure and safe (relatively)
• Platform-Independent (Architecture-Neutral)
• Distributed and Portable
• Fast (but not the fastest)
• Multithreaded

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Object Oriented Programming

• Encapsulation keeping data and its related
  functionality together (non-OOP left them
  independent)
• Data hiding providing an interface to the user,
  and hiding the implementational details of this
  interface. This leads to simpler programming
  tasks.
• Inheritance ability for one class to inherit
  properties (data and functionality) from other
  classes. This leads to reusable code. (Classes
  are arranged in a hierarchy of classes
  (categories) and subclasses (sbucategories)
• Polymorphism ability for the same message to be
  interpreted by objects of different types in
  different ways.

Instances
Classes
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The Java Programming Process
Write Source Code in Java
java.exe is the VIRTUAL MACHINE
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Anatomy of a Java Program

• Comments documentation. Compiler ignored these.
• Reserved Words keywords of the language.
• Modifiers keywords that describe properties of
  methods, classes, or variables.
• Statements action instructions telling the CPU
  what to do.
• Blocks groups of statements enclosed in and
  
• Classes object-oriented constructs involving
  methods and variables arranged in inheritance
  hierarchies.
• Methods functions, members of classes.
• The main method the starting point of a Java
  application.
• Package group of related classes.

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A Simple Application

• Example 1.1
• //Welcome.java This application program prints
• // Welcome to Java!
• package chapter1
• public class Welcome
• public static void main (String args)
• System.out.println("Welcome to Java!")

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A Simple Application

• Example 1.1
• //Welcome.java This application program prints
• // Welcome to Java!
• package chapter1
• public class Welcome
• public static void main (String args)
• System.out.println("Welcome to Java!")

Commentsuse // for single line or / / for
multiple lines
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A Simple Application

• Example 1.1
• //Welcome.java This application program prints
• // Welcome to Java!
• package chapter1
• public class Welcome
• public static void main (String args)
• System.out.println("Welcome to Java!")

Package indicates a grouping of classes.
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A Simple Application

• Example 1.1
• //Welcome.java This application program prints
• // Welcome to Java!
• package chapter1
• public class Welcome
• public static void main (String args)
• System.out.println("Welcome to Java!")

Reserved words keywords of the language with
specific meaning to the compiler.
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A Simple Application

• Example 1.1
• //Welcome.java This application program prints
• // Welcome to Java!
• package chapter1
• public class Welcome
• public static void main (String args)
• System.out.println("Welcome to Java!")

Modifiers reserved words that specify
characteristics or properties of data, methods,
and classes.
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A Simple Application

• Example 1.1
• //Welcome.java This application program prints
• // Welcome to Java!
• package chapter1
• public class Welcome
• public static void main (String args)
• System.out.println("Welcome to Java!")

Statements action instructions. Always end with
semicolon ()
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A Simple Application

• Example 1.1
• //Welcome.java This application program prints
• // Welcome to Java!
• package chapter1
• public class Welcome
• public static void main (String args)
• System.out.println("Welcome to Java!")

Blocks groups of statements (sometimes called
compound statements). Enclose classes, method
statements, or statements inside controls
structures. Can be nested.
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A Simple Application

• Example 1.1
• //Welcome.java This application program prints
• // Welcome to Java!
• package chapter1
• public class Welcome
• public static void main (String args)
• System.out.println("Welcome to Java!")

Classes complex data structures encapsulating
data and actions. Classes are composed of methods
(functions) and variables (attributes)
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A Simple Application

• Example 1.1
• //Welcome.java This application program prints
• // Welcome to Java!
• package chapter1
• public class Welcome
• public static void main (String args)
• System.out.println("Welcome to Java!")

Methods named blocks of statements that can be
called, take arguments (parameters), return
values. Note all Java applications must have a
main method as an entry point to the program.
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Options for Building and Running Java Applications

• Command Line (in DOS mode)
• Get into command window
• Call JDK programs for operations
• Text-mode debugging
• Using an Integrated Development Environment (e.g.
  NetBeans)
• GUI interface
• Menus/toolbars for operations
• Graphical debugging

Well discuss this later
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Suns Java Development Kit (JDK)

• Includes the following tools
• found in bin subdirectory of the java directory
• Java Compiler (javac.exe)
• Java Virtual Machine (java.exe)
• Java AppletViewer (AppletViewer.exe)
• Java Debugger (jdb.exe)
• Where to get the JDK
• from http//java.sun.com/javase/downloads/netbeans
  .html
• also includes Netbeans IDE

Its Free and Open Source!!!
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Using Command-Line Technique for Writing,
Compiling and Running Java Applications

• Use any text editor to create your .java source
  code file (for example, Notepad).
• Copy the compile.bat and run.bat files (available
  for download from my web site) to the same folder
  as your .java source code file.
• Make sure the path in the batch files are correct
  (see next slide).
• Use the Command Prompt (DOS window) to access the
  folder and run the batch files.

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File Paths

• If you installed the Java SDK and NetBeans from
  Suns Java Site, the path to your file will be
• c\Program Files\Java\jdk1.5.0_12
• If you are using java in the lab (installed on
  the D drive), the path to the JDK is
• D\Program Files\Java\jdk1.5.0_12

In both cases, the javac.exe and java.exe
programs are in the bin subfolder
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What is NetBeans?

• Integrated Development Environment (IDE)
• Analogous to Microsoft Visual Studio
• Tools include
• Project workspace
• Color-coded, smart editing
• GUI building tools (e.g. form builders)
• Compiler
• Execution
• Debugging tool

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What is NetBeans? (continued)

• Can build entire projects consisting of multiple
  source files and classes
• Includes GUI building tools for easy placement of
  components (controls)
• Like form builders in VB
• Menu/toolbar interfaces for compile/execute/debug

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NetBeans Interface (for edit, compile, execute,
and debug)
Projects window
Editor window
Output window
Debug windows
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Using the Examples from Liangs Textbook

• All Textbook examples are located downloadable
  from my web site.
• Create a Liang7eSamples project using NetBeans.
• In the Liang7eSamples folder, there is a src
  subfolder. In that subfolder, you can copy the
  folders I provide in my exampleseach subfolder
  of src is a package, and contains the java
  programs of the chapter
• NOTE Liang has a web site with more resources
  http//prenhall.com/liang.