Lecture Summary 1

Introduction to Java

• A brief history
• January 1996: first official release JDK 1.0
• Web: applets, security, URL, networking
• GUI: Abstract Windows Toolkit (AWT)
• February 1997: JDK 1.1
• Authentication: digital signatures, certificates
• Distributed computing: RMI, object serialization,  Java IDL/CORBA
• Database connectivity: JDBC
• Component architecture: JavaBean
• December 1998: Java 2 Platform (JDK 1.2):
• Standard (J2SE), Enterprise (J2EE), and Micro (J2ME) Editions
• JFC: Swing, Java2D, Java3D
• Java Cryptography Extension (JCE)
• Enterprise computing: enterprise JavaBean (EJB),  servlets, Java server page (JSP), Jini, XML
• Java Multimedia Framework  (JMF)
• Embedded systems: KVM, JavaCard
• Performance enhancement: JIT, HotSpot VM
• May 2000: J2SDK v1.3
• Enhancements in features, performance, and security.
• May 2001: J2SDK v1.4 beta
• XML, XSLT, JCE, etc. all included in J2SE
• Numerous enahnacements: I/O, assertions, regular expression, logging, etc.
• 2002(?): J2SDK v1.5
• Generic types
• Main characteristics of Java
• Simple
• Object-oriented
• Statically typed
• Compiled
• Architecture neutral
• Garbage collected
• Multi-threaded
• Robust
• Secure
• Extensible

Installing JDK 1.3 or higher (required)

• Obtain the installation file of the platform of your choice.
• For Windows 9x/NT/2000, JDK 1.3 is on the CD.
• For other platforms or a newer version, download from Sun Microsystems http://java.sun.com/
• Follow the installation instruction.
• On Windows 9x/NT/2000, run the executable installation file, e.g., j2sdk1_3_0-win.exe.
• Download and install the JDK API documemtation from Sun Microsystems
• Use Java API documentations.

Installing BlueJ (optional)

Download from http://www.bluej.org/

Make sure JDK is installed

Follow the installation instruction

Download the BlueJ Tutorial

Your first Java program

Source code: HelloWorld.java

Compile: javac HelloWorld.java

Run: java HelloWorld

Using BlueJ

Java basics

• Program structure, naming convention,
• Packages
• Java provides mechanisms to organize large-scale programs in a logical and maintainable fashion.
• Class --- highly cohesive functionalities
• File --- one class or more closely related classes
• Package --- a collection of related classes or packages
• The Java class library is organized into a number of packages:
• java.lang --- general
• java.awt --- GUI
• java.io --- I/O
• java.util --- utilities
• java.applet --- applet
• java.net --- networking
• Import
• Example Time.java
• Use import
• Example Time1.java
• Use fully qualified class name
• Identifiers
• Reserved words
• Data types
• Primitive types:

Datatype	Meaning	Size in Bytes	Min Value	Max Value	Sig. Digits
byte	Integer	1	-128	127
short	Integer	2	-32,768	32,767
int	Integer	4	-2 billion	2 billion
long	Integer	8	-9.2x1018	9.2x1018
float	Floating Point	4	-3.2x1038	3.2x1038	7
double	Floating Point	8	-1.8x10308	1.8x10308	15
char	Character	2	Any Unicode character
boolean	boolean	1	false	true

• Boolean type: boolean
• Boolean constants:

true
false
• Integer types: int byte short long
• Examples of integer constants:

354
-37
0
246543
• Floating point type: double float
• Examples of floating point constants:

4.642
-0.034
5.98e24
9.11e-31
• Character type: char
• 16-bit Unicode character.
• ASCII is a subset of Unicode --- ISO-8859 (Latin-1)
• Examples of character constants:

'A'
'y'
'8'
'*'
' ' (space)
'\n' (new line).
• Escape sequences:

 

\b	backspace
\f	form feed
\n	new line (line feed)
\r	carriage return
\t	tab
\"	double quote
\'	single quote
\\	backslash

\uhhhh: hex-decimal code, e.g. \u000A
\ddd: octal code, e.g. \040

• Class types:
• String
• Examples of string literals:

"watermelon"
"fig"
"$%&*^%!!"
"354"
" " (space)
"" (empty string)
• constructor
• operator + and +=
• methods:
• charAt(int i)
• length()
• Primitive type conversion:
• widening
• narrowing
• Arithmetic operators and expressions
• +   addition
• -  subtraction
• *  multiplication
• /  division
• %  remainder
• precedence and association
• Example: Time2.java
• Use Calendar class. Mixed-type string concatenation.
• Variable declaration and initialization
byte maxAge;
short timeInSeconds;
int x, y, z;
long count;
char a, b;
boolean flag;
float massInKilos;
double maxVal;

short timeInSeconds = 245;
char a = 'K', b = '$';
boolean flag = true;
double maxVal = 35.875;

• Assignments
total = quantity * unitPrice;
count = count + 1;
count += 1;
count++;