Object-Oriented Programming (Java)
2014.2.26
Course Information
• Lecturer: 熊运余
Assist ：张乾初 QQ1053240123
• Contact:
– 3149102@qq.com, 18980704280
• Course website:
QQ交流群：
296340622
– http://cc.scu.edu.cn/2226.html
– 兴趣题目JAVA地图、移动互联网开发
2
CTE Curriculum
1: Introduction to
Information Systems
2: Introduction to
Computer Systems
4 : User Centered
Design and Testing
3: Object Oriented
Programming and
Design
7: Database
Systems
5: Data Structures
and Algorithms
6: System Level
Programming
9: Software
Specification, Test
and Maintenance
10: Software
Project Organization
and Management
8: Networks and
Distributed
Computing
3
Schedule
• 学时：64学时
• 课堂教学：32学时 ，实验：32学时
• 学分：4学分
4
Contents
•
•
•
•
•
•
Java Application Basic (2 weeks)
Class design and implementing (4 weeks)
Advanced class design (2 weeks)
File I/O and GUI（2week)
Design Pattern（3 weeks）
Java Advanced Tech (2 week)
5
Emphases
• Object Oriented concepts including inheritance,
polymorphism, abstract classes, and interfaces
• Object Oriented Designs using UML
• Advanced Java Class
• Design Pattern
• Practice
6
Assessment
• 50% Final Examination;
• 50% On-class laboratory practice and homework.
7
Attendance, Late Work, Repeat Work
• Attendance:
– Absences need not be excused.
• Late Work:
– It is generally not accepted and receives a zero.
– In the case of unplanned emergencies, speak to the
instructor for a revised due date.
• Repeat Work (Retakes):
– The course will not give makeup.
– Multiple-choice assessments can be retaken for a
higher grade.
8
Your Role – Learning With Doing
• Attend all lectures
• Attend all laboratory classes
• Work out the exercise on your own or after a
discussion with your group, don’t make copy
• Come to see me during lecture, consultation hour
and laboratory session
9
You end up learning more in less
time when you are actually doing
stuff instead of just reading.
Reference Book & Course Material
• Beginning Java Objects_From Concepts to
Code_Second Edition
• Deitel & Deitel, Java How To Program, Six
Edition.
• Thinking in Java, Bruce Eckel
• http://java.sun.com (Oracle)
• http://java.sun.com/docs/books/tutorial/
11
Topics Covered Today
• Unit 1.1 Java Applications
– 1.1.1 Applications in Java
12
1. Java Basic
• JAVA source code is first written in plain text files
ending with the .java extension.
• Those source files are then compiled into .class
files by the Java compiler (javac).
– A .class file does not contain code that is native to your
processor;
– it instead contains bytecodes(字节码) -- the machine
language of the Java Virtual Machine.
• The Java launcher tool (java) then runs your
application with an instance of the Java Virtual
Machine.
13
JAVA Technology
14
Platform-Independent
15
The Java Platform
• The Java platform is a software-only platform
that runs on top of other hardware-based
platforms.
• The Java platform has two components:
– The Java Virtual Machine
– The Java Application Programming Interface (API)
16
Java Virtual Machine
• A Java Virtual Machine (JVM) enables a set of
computer software programs and data structures to use
a virtual machine model for the execution of other
computer programs and scripts. The model used by a
JVM accepts a form of computer intermediate
language commonly referred to as Java bytecode.
17
Java Platform
Platforms
J2SDK
J2EE
J2ME
Core/Desktop
Enterprise/Server
Mobile/Wireless
Application,Applet,
Swing, Awt
JSP/Servlet, EJB
Midlet (Cell Phone/PDA)
Borland JBuilder,
JCreator, or Text
Editor
IBM WebSphere, WSAD
BEA WebLogic, Workshop
Sun One Studio
Oracle JDeveloper
18
Nokia, Motorola,
Siemens SDK
JBuilder,Sun One
Studio
Difference between Java and C
• Java is derived from C
• Many of its syntactic characteristics are similar to C
• However, there are some huge differences
19
Expressions
• Arithmetic operators are the same:–
+, –, *, /, %, ++, ––
• Numerical type conversion is mostly the same
– Java spells out divide by zero, NaN (not a number, etc.)
– C & C++ are machine dependent
20
Relational Operators
• Relational operators work the same way but return
different results:–
>, >=, <, <=, ==, !=
• In Java, they return values FALSE and TRUE
• In C/C++, they return values 0 and 1
• In C/C++,
– a value of zero means false
– any value that is not zero means true
– E.g., 1, 5, -1000000, 3.14159, 6.626068 × 10-34
21
Conditional and Bitwise Operators
• Conditional execution operators are same in Java and
C/C++:–
||, &&, !
• Bitwise operators are same in Java and C/C++:–
|, &, ^ for bit-by-bit operations with a word
• Shift operators differ a little bit
<< (left shift) is the same
>> (right shift) is machine dependent in C/C++
• I.e., whether to fill from left with zeros or sign bits
22
Assignment and Unary Operators
• Assignment operators work the same:–
=, +=, -=, *=, /=, &=, |=, ^=
• The following unary operators are available C/C++ but
not in Java
~
invert the bits of a word
*
pointer creation
&
pointer dereference
sizeof
# of bytes in operand or data type
->
pointer dereference with field selection
There is no pointer in Java.
23
Formatted Input & Output
• Very different between C and Java
• Very different between C and C++
• Handled by library functions in C
• printf()
• scanf()
• getc()
• putc()
• Many others!
24
printf() – Print formatted data
printf("string containing '%' specifiers",
expr1, expr2, expr3, …);
• Copy the string, character-by-character, to
the output.
• When the ith '%' is encountered, treat it as a
conversion specifier for converting the value
of expri
• Copy the converted value to the output per
instructions encoded in the conversion specifier
• Return number of characters printed
25
printf() conversion specifiers
• %d or %i
• Treat expression as a decimal number (with sign)
• %u
• Treat expression as unsigned decimal number
• %f
• Treat expression as double precision floating point number; print without
exponent
• %e or %E
• Treat expression as double precision floating point number; print with
exponent (base 10) — scientific notation
• %c
• Treat value of expression as the code for a single character
• %s
• Treat expression as a pointer to a string
• …
Later in this
course
26
printf() conversion specifiers (continued)
• Conversion specifiers may optionally contain
• Right or left alignment in the field
• Minimum field width (padded on right or left)
• Precision – i.e.,
– Maximum length of string
– Number of decimal places of floating point value
• Examples
%6d – print signed decimal number in 6-char field
%8.4f – print floating point number with four places after
decimal point, field width of 8 characters
27
scanf() – Scan formatted data
scanf("string containing '%' specifiers",
&var1, &var2, &var3, …);
• Scan the input, matching the string character by
character.
• When the ith '%' is encountered, treat as a
conversion specifier for converting next sequence
of characters and storing result in vari
• Copy the converted value to the output per instructions encoded
in the conversion specifier
• Stop if input does not match string or conversion
not successful
• Return number of successful conversions.
28
scanf() – Typical Usage
int j;
double x;
scanf("%d%f", &j, &x);
• Scan the input, skipping blanks and tabs
• Try to match a signed integer; if successful, store
result in j
• Continue scanning, skipping blanks and tabs
• Try to match a floating point number. If successful,
store in x
• Return number of items stored.
29
Primitive types
• In C, the primitive types are referred to using a combination of the
keywords char, int, float, double, signed, unsigned, long, short and
void. The allowable combinations are listed below, but their
meanings depend on the compiler and platform in use, unlike Java.
unsigned int
unsigned char
• Java primitive types
long (8bytes) int (4bytes) double (8bytes) float (4bytes)
boolean (true, false) char (2bytes)
30
Classes instead of structures
• C structure is like a Java class, and all parts are
visible to any code that knows the declaration.
• For example in C:
struct point
{
int x, y;
};
31
Type aliasing
• New names or aliases for existing types may be
created using typedef. For example:
typedef int int32_t;
There is no equivalent of type aliasing in Java.
32
Preprocessing
• There is no equivalent of preprocessing in Java
– Macro
#define PI 3.1415926
– Header file
#include "mydecls.h"
– Conditional compilation
#if
#else
33
Enumerations and Unions
• In C
enum light { RED, REDAMBER, GREEN, AMBER };
union number
{
char c;
int i;
float f;
double d;
};
• Java 1.5 has introduced a new enum family of
classes with greater type-safety, and a few other
nice facilities. Java does not have unions.
34
Global Variables
• In C
extern int giNumOfPoints;
• In Java
class Contour {
public static int iNumOfPoints;
}
usage of the variable: Contour.iNumOfPoints
There is no attribute definition outside class in Java. Java is a pure
object-oriented programming language. (attribute/method)
35
2. Applications in JAVA
• Java programs can be called from Web pages or
run stand alone.
– When launched from a Web page, the program is
called a Java “applet.” (JavaScript)
– When a non Web-based Java program is run on a user's
machine, it is a stand-alone Java "application."
– When running in a Web server, it is a Java "servlet."
(JSP/Servlet, JSF, Portlet, J2EE/EJB,Web Services,
JNLP)
36
Applications
• An application is a stand-alone program that runs
locally.
• Applications can use console I/O, or can have a
GUI developed using the Java class library.
• Applications have no system resource restrictions.
37
Running a Java Application
You write
Java code
using an
editor
Text Editor
Java code:
MyProg.java
You run the
Java
compiler
'javac'
You execute the
bytecode with the
command 'java'
javac MyProg.java
You save the
file with a
.java
extension
Bytecode:
MyProg.class
This creates a
file of
bytecode with
a .class
extension
java MyProg
Output
38
Creating an Application
 Open "Notepad" (Start  Programs  Other  Notepad)
 Type this in:
 Save As
“MyApplication.java"
 Open a DOS Window
(Start  MS-DOS
Prompt)
public class MyApplication {
public static void main(String args[]) {
System.out.println(
"This is my first application!");
}
}
 Type javac myApplication.java
 If you type dir MyApplication.* you should see MyApplication.java and
MyApplication.class
If it gives an error check you typed it in exactly right.
39
Running the Program
In the DOS window type java MyApplication
D:\> java MyApplication
You should see
something like this:
This is my first application!
D:\>
40
What does it mean?
This line announces that the program
(class) can be run by anyone (public), is
called MyApplication.
This line declares a main method.
It has one input argument. The
operating system begins
execution by calling main.
public class MyApplication {
public static void main(String args[]) {
System.out.println(
“This is my first application!”);
}
}
This line tells the computer to
display some text ( a string) on
the screen.
This is what is displayed.
41
Java Applets
• An applet is a little Java program that can run
inside a Web browser.
• It typically shows up inside a rectangular area
(which may be transparent) on the browser screen.
42
Applet Restrictions
• Security issues are important, since the provider of an
applet may not be trustworthy.
• Applets can’t touch your system resources (file system,
OS, etc.), although some browsers give extra privileges to
“trusted applets”. For instance an Applet cannot:
–
–
–
–
–
Access local files
Delete local files
Run another program
Find out your name
Connect to another host
• Applets can be slow, since the whole thing must be
downloaded each time it’s run.
43
Running a Java Applet
You write Java
code using an
editor
Java code:
MyApp.java
Text Editor
You run the Java
compiler 'javac'
javac MyApp.java
You save the file
with a .html
extension
You write a
web page in
html using an
editor
Text Editor
You can view the applet with the
command 'appletviewer'
You save the file
with a .java
extension
This creates a file of
bytecode with a .class
extension
Bytecode:
MyApp.class
Web page:
MyApp.html
appletviewer MyApp.html
44
You can view the web
page from a web
browser
Web Browser
Window
Creating an Applet
 Open "Notepad" (Start  Programs  Other  Notepad)
 Type this in:
 Save As
“MyApplet.java"
 Open a DOS
Window (Start 
MS-DOS Prompt)
import java.applet.*;
import java.awt.*;
public class MyApplet extends Applet {
public void paint(Graphics g) {
 Type javac
MyApplet.java
g.drawString("This is an applet!\n", 10, 10);
}
}
 If you type dir MyApplet.* you should see MyApplet.java and
MyApplet.class
45
Creating the Web Page
In order to run an applet you have to embed it in a web page
using a special <applet> tag e.g:
<applet code="name.class" width=www height=hhh></applet>
Using Notepad type in the following
and save it as "Greetings.html":
Size of the applet
in pixels
<html>
<head>
<title>Greetings Applet</title>
</head>
<body>
<applet code=“MyApplet.class" width=300 height=200 ></applet>
</body>
</html>
46
Running the Program
In the DOS window type appletviewer Greetings.html
G:\> appletviewer Greetings.html
You should see
something like
this:
47
Running in a Web Browser
Open Greetings.html in browser such as Netscape, IE or
Firefox, you should see something like:
Title
Your
greeting
Message
48
What does it mean?
These 2 lines tell the computer to
include (import) two standard
libraries awt (Abstract Window
Toolkit) and applet.
This line announces that the
program (class) can be run
by anyone (public), is called
MyApplet and is an Applet.
This line declares
what follows in the {
} as a method called
paint.
import java.awt.*;
import java.applet.Applet;
public class MyApplet extends Applet {
public void paint(Graphics g) {
g.drawString("Hello World!", 50, 50);
}
}
This line tells the
computer to display
some text ( a string)
on the screen.
This is what is
displayed
49
This is where it is
displayed in pixels
across and down from
the top left hand corner
Things to remember
• Everything in Java is case sensitive - Paint is not the
same as paint.
• The file containing the source code must have the same
name as the class it contains and use the .java extension.
For instance: MyApplet should match the name of the
file MyApplet.java (not myApplication.java).
• Curly brackets { and } are used to group parts of the
program called blocks together. Blocks can be nested
inside other blocks but each { must be matched with a }.
• Most statements require a semi-colon ; at the end. A
statement can continue on the next line if necessary.
• Spaces are not important - it is recommended to indent
blocks for clarity.
50
Java Demos*
• http://worldwind.arc.nasa.gov/java/demos/
51
3. Java Coding Environment
• Getting and Installing Java SE
–
–
–
–
Java 2 Platform, Standard Edition 5.0 (Java SE 5.0 “Tiger”).
J2SE(TM) Development Kit Documentation 5.0
http://java.sun.com/javase/downloads/index.jsp
Java SE 6 “Mustang”
• Follow the SSD3 Appendix B to setup your coding
environment.
• Bookmark the Java SE API so you can always get to it
easily. Or, just bookmark the index page on Sun’s Java
Web site.
52
Discussion – Java Performance
• Programs written in Java have a reputation for being
slower and requiring more memory than those written in
some other languages. However, Java programs'
execution speed improved significantly with the
introduction of Just-in-time compilation in
1997/1998 for Java 1.1, the addition of language features
supporting better code analysis (such as inner classes,
StringBuffer class, optional assertions, etc.), and
optimizations in the Java Virtual Machine itself, such
as HotSpot becoming the default for Sun's JVM in 2000.
53
Java简介
 History
– Java语言之父 James Gosling
– 1992年，Sun公司的FirstPerson小组，开发手机、
PDA应用软件，最初使用的是C++语言。
– 小组转移到交互式电视机机顶盒的开发，oak语言，即Java的前身。
– 1994年，Internet开始受到关注，需要一个小巧、健壮、平台无关的语言，oa
k改头换面成为Java。
– 1996年，Java编译器的第一版发布。
– 1997年，Sun公司推出Java1.1（JDK1.0）。
– 1998年，Sun公司推出Java2（JDK1.2）。
– 2004年，J2SE1.5发布，是Java语言发展史上的又一里程碑事件。为了表示这
个版本的重要性，J2SE1.5更名为J2SE5.0。
– 2005年，J2SE6.0发布; J2EE:Java EE;J2SE:Java SE;J2ME:Java ME.
– 2009年4月，Sun被甲骨文收购,其中包含Java技术.
54
Java简介
 Java的特点
◇
分布式
– 数据分布和操作分布
– Java支持B/S计算模式
– Java提供了一整套网络类库
◇
安全性、可靠性
– 强类型语言
– 摒弃了指针类型
– GC 自动垃圾回收、异常处理机制、运行时检查
◇ 多线程
55
Java简介
 Java开发环境
– 设置系统环境变量
JAVA_HOME= C:\Sun\AppServer\jdk （JDK的安装目录）
classpath += .;%JAVA_HOME%\lib\dt.jar;
%JAVA_HOME%\lib\tools.jar;
path += ;%JAVA_HOME%\bin
56
Java简介
 JDK的实用工具
◇ Java
调试器
○
是一个基于命令行的调试工具，可以逐行执行
程序，
设置断点和检查变量的值等。
Jdb [options] class
◇ Applet
浏览器
○
是一种用于执行HTML文件上的java小程序的java
浏器。
Appletviewer [-debug] html文件名
57
Java简介
 测试开发环境
58
Java简介
 测试开发环境
源文件：HelloJC.java
编译
59
Java简介
 测试开发环境
运行
60
Java简介
 Java的注释
– 两种注释风格
/*
//：
○
*/：
/* This is a comment that
continue across lines */
//This is a one-line comment
养成良好的编码风格，对代码多加注释
61
 Java语言基础
 Java的标识符
– 标识符
字符数字序列。在Java语言里，标志符以字
符或_ , $开头，后面可以包含数字，标志符是大小
写有区别的，没有长度限制。
示例
合法标志符：nVariable , $Variable ,
_Variable
非法标志符：2007Variable , new，Interger
62
Java语言基础
 Java的分隔符
– 分隔符用来使编译器确认代码在何处分隔
– ( ) [ ] { } ; ,
. 都是Java语言的分隔符
– 例：i = p-k; //;表示一行语句的结束
63
Java语言基础
 Java的变量与常量
– 常量
在程序运行期间不能改变的量。
利用final关键字来定义常量。
○
定义格式：final type name = value;
例：final double PAI = 3.14；
64
Java语言基础
 Java的基本数据类型
– 字符类型
用单引号括( ‘ ’ )起来的一个字符常量，
用双引号括( “ ” )起来的表示一个字符串。
含义
示例：字符
‘ a ’, ‘ B ’
\’
单引号字符
\\
反斜杠
\r
回车
\n
换行
\f
走纸换页
\t
横向跳格
\b
退格
注意：字符串不属于简单数据类型，它被当作Java所提
供的String类的一个对象来处理。
65
Java语言基础
 Java的运算符
– 二元算术运算符
运算符
使用方法
功能说明
+
op1+op2
操作数1加操作数2
-
op1-op2
操作数1减操作数2
*
op1*op2
操作数1乘操作数2
/
op1/op2
操作数1除操作数2
%
op1%op2
操作数1和操作数2的模
66
Java语言基础
 Java的运算符
– 位运算符
操作符
使用方法
功能说明
&
|
op1&op2
op1|op2
按位与
按位或
^
~
<<
>>
op1^op2
~op1
op1<<op2
op1>>op2
按位异或
按位取反
op1左移op2位
op1右移op2位
>>>
op1>>>op2
op1无符号右移op2位
67
Java简介
 Java程序开发的生命周期
68