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Huazhong University of Science and Technology
JAVA Programming Language
Lecture 1:Introduction
Jing XU
School of Electronic Information and Communications
Huazhong University of Science and Technology
Huazhong University of Science and Technology
Instructor

How to contact me?
Email: xujing@hust.edu.cn
Web: http://itec.hust.edu.cn/~xujing
Jing XU
 Course
Computer Network
 C Programming Language
 Java Programming Language

 Research
(@ITEC)
Wireless Networks, such as CRNs, WMNs, …
 Human Behavior on Internet

 Programming

C, C++, Java, Linux/Unix Programming, …
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Lecture 1

Introduction of this course
 Why?
 Goals
 Textbook
 Course

Schedule
Chapter 1
 Java
History
 What is Java?
 Java Nowadays
 Quick view to Java Applications
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Why we need Java Language?
Java has dominated over 20% quotient of the
computer language market.
 http://spectrum.ieee.org/computing/software/top-10-programming-languages
 http://redmonk.com/sogrady/2015/01/14/language-rankings-1-15/
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What is programming

What is programming?
 The
process of designing, writing, testing, debugging /
troubleshooting, and maintaining the source code of
computer programs.

What is programming language?
 This
source code is written in a programming language
 The purpose of programming is to create a program that
exhibits a certain desired behavior
 Java and C/C++ are the most two widely supported
programming language
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Goals of this course

Understanding the fundamental programming
concepts on Java Programming,
 Data

types, Controls, methods (i.e. functions), …
Understand the idea of object-oriented
software design, can do simple design
 Class,

Object, Inheritance, …
Understand the advanced application of JAVA
 Thread,
I/O, socket programming, …
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Reference textbooks
[1] H.M.Deitel, P.J.Deitel, Java How to
Program, 8th , Pearson 2012.
[2] Y.Daniel Liang, Prentice Hall, Introduction to
Java Programming(brief version), Pearson 2011.
[3] Cay S. Horstmann, Prentice Hall, Core Java 2
(Vol.1) & (Vol. 2), Prentice Hall,2004.
[4] Bruce Eckel, MindView Inc, Thinking in Java,
3rd, President, MindView, Inc，2003.
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Course Schedule
An introduction to Java
 Variable and data type
 Operators and control statement
 Basic Object-Oriented programming concept
 Inheritance
 Polymorphism
 Java Exception handling
 Java database access

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Evaluation and requirements

Evaluation Criterion
 Attendance
check (20%)
 Programming assignments (40%)
 Final Examination (40%)

Requirements
 Lecturing:
English
 Programming ability
 Final Paper Test
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Tips and suggestions
More work should be done after lecture hours.
1.
First of all, practice in programming
2.
Read textbook before/after lecture
3.
Read other English reference textbooks
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CONCEPTS IN JAVA
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Concepts in Java

Java


JDK: Java Development Kit



Java development core part, including JRE, Java tool set and Java class
library
J2EE, J2SE, J2ME (from Java 1.5, currently 1.8)
JRE: Java Runtime Environment



A simple, object-oriented, distributed, interpreted, robust, secure,
architecture-neutral, portable, high-performance, multi-threaded, and
dynamic language (from Java whitepaper)
All the programs must be executed in JRE
JVM, Java core class library, and supported files
JVM: Java Virtual Machine



A part of JRE
An virtual computer generated by Java platform, it has its own
hardware arch, such as the processor, stacks, registers etc, even the
instruction systems
Translate the bytecode to the CPU instructions or system functions
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What is Java?
Fully support O-O Programming
 Small, simple and portable

 Java
was designed to be small, simple, and portable
across platforms and operating systems

Java is not only a kind of programming
language, but also a software programming
running environment or platform
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J2EE, J2SE and J2ME
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Java, J2SE, JDK & JRE
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Who develops Java?


The Java language was developed at Sun
Microsystems in 1991 as part of a research
project to develop software for consumer
electronics devices.
Java is a programming language and
environment whose original name was Oak and
developed as a part of the Green project at Sun
started by James Gosling.
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Java’s initial goal
Java’s goals at that time were to be small, fast,
efficient, and easily portable to a wide range of
hardware devices.
 It is those same goals that made Java an ideal
language for distributing executable programs
via the World Wide Web.
 “Write once, run anywhere!”

 http://www.oracle.com/technetwork/java/javase/overview/javahistory-index-198355.html
 http://oracle.com.edgesuite.net/timeline/java/
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Java history

1991


1992


Java is open sourced
2007


Technology that change our daily lives
2006


The world takes Notice
2000


An Innovation before its time
1995


Exploring green fields in consumer electronics
Making rich internet application easier to build (JavaFX)
2014

A new version of JDK with great changes
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Java’s application nowadays
Enterprise information system
 Mobile application
 Distributed computing
 Web services
 Grid

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The Types of Java Programs

Java Application
 Run
on local computer
 Based on J2SE

Java Applet
 Run

Java Servlet
 Run

on web browser
on application server
JavaBeans
 Cannot

run independently
Enterprise JavaBeans
 Run
on application server
 Based on J2EE
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Java’s Features
Simple
 Object-Oriented language
 Distributed
 Robust
 Secure
 Architecture-Neutral
 Multithread
 Dynamic

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QUICK VIEW TO JAVA
APPLICATION
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Quick View to Java Application
1 // Sample 01: Welcome1.java
2 // Text-printing program.
3
4 public class Welcome1 {
5
6 // main method begins execution of Java application
7 public static void main( String[] args )
8 {
9
System.out.println( "Welcome to Java Programming!" );
10
11
} // end method main
12
13} // end class Welcome01
Output:
Welcome to Java Programming!
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Quick View to Java Application
Output:
Welcome to Java Programming!
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Quick View to Java Application
1 // Sample 01: Welcome1.java

Comments start with: //
 Comments
ignored during program execution
 Document and describe code
 Provides code readability

Traditional comments: /* ... */
/* This is a traditional comment. It can be split over many lines */
2 // Text-printing program.

Another line of comments

Note: line numbers not part of program, added for reference
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Quick View to Java Application
3

Blank line
 Makes program more readable
 Blank lines, spaces, and tabs are
 Ignored by compiler
4

white-space characters
public class Welcome01 {
Begins class declaration for class Welcome01
 Every Java program has at least one user-defined
 Keyword: words reserved for use by Java
 class keyword followed by class name
 Naming classes: capitalize every word
 SampleClassName, UndergraduateStudent, …
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class
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Quick View to Java Application
4

public class Welcome01 {
Name of class called identifier
 Series
of characters consisting of letters, digits,
underscores ( _ ) and dollar signs ( $ )
 Does not begin with a digit, has no spaces
 Examples: Welcome1, $value, _value, button7

7button is invalid
 Java

is case sensitive (capitalization matters)
a1 and A1 are different
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Quick View to Java Application
4 public class Welcome01 {

Left brace {
 Begins
body of every class
 Right brace ends declarations (line 13)
7 public static void main( String args[] )

Part of every Java application
 Applications
begin executing at main
Parenthesis indicate main is a method
 Java applications contain one or more methods

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Quick View to Java Application
7 public static void main( String args[] )
 Exactly

one method must be called main
Methods can perform tasks and return
information
 void means
main returns no information
8 {

Left brace begins body of method declaration
 Ended
by right brace } (line 11)
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Quick View to Java Application
9 System.out.println( "Welcome to Java Programming!" );

Instructs computer to perform an action
 Prints string of characters
 String - series characters inside double quotes
 White-spaces in strings are not ignored by

System.out
compiler
 Standard
output object
 Print to command window (i.e., MS-DOS prompt)

Method System.out.println
 Displays line of text
 Argument inside parenthesis

This line known as a statement
 Statements
must end with semicolon ;
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Quick View to Java Application
11
} // end method main
 Ends
method declaration
13 } // end class Welcome01
 Ends
class declaration
 Can
add comments to keep track of ending braces
 Comments can start on same line after code
 Remember, compiler ignores comments
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Quick View to Java Application

Saving files
name must be class name with .java extension
 Welcome1.java
 File

Compiling a program
 Open
a command prompt window, go to directory
where program is stored
 Type javac Welcome1.java
 If no errors, Welcome1.class created
Has bytecodes that represent application
 Bytecodes passed to Java interpreter

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Quick View to Java Application

Executing a program on CMD model
 Type
java Welcome01
Interpreter loads .class file for class Welcome1
 .class extension omitted from command

 Interpreter
calls method main
Executing Welcome1 in a Microsoft Windows Command Prompt.
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A modified Welcome01 sample
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Thanks!
Jing XU
ITEC, EIC, HUST
Email: xujing@hust.edu.cn
Website: http://itec.hust.edu.cn/~xujing
Huazhong University of Science and Technology
Platform-independent
Other Language
Java Platform
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