Transcript Advanced Java Programming CSE 7345 / NTU 538N

Welcome Back!!!
Advanced Java Programming
CSE 7345/5345/ NTU 538N
Session 2
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Office Hours:
by appt
3:30pm-4:30pm
SIC 353
Chantale
Laurent-Rice
Welcome Back!!!
[email protected]
[email protected]
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Introduction
• Chapter 1
– Course Objectives
– Organization of the Book
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Objectives
• Upon completing this chapter, you will
understand
– Create, compile, and run Java
programs
– Primitive data types
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Book Chapters
• Part I: Fundamentals of Programming
– Chapter 1 Introduction to Java
– Chapter 2 Primitive Data Types and
Operations
– Chapter 3 Control Statements
– Chapter 4 Methods
– Chapter 5 Arrays
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Book Chapters, cont.
• Part II: Object-Oriented Programming
– Chapter 6 Objects and Classes
– Chapter 7 Strings
– Chapter 8 Class Inheritance and
Interfaces
– Chapter 9 Object-Oriented Software
Development
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Book Chapters, cont.
• Part III: GUI Programming
– Chapter 10 Getting Started with GUI
Programming
– Chapter 11 Creating User Interfaces
– Chapter 12 Applets and Advanced GUI
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Book Chapters, cont.
• Part IV: Developing Comprehensive
Projects
– Chapter 13 Exception Handling
– Chapter 14 Internationalization
– Chapter 15 Multithreading
– Chapter 16 Multimedia
– Chapter 17 Input and Output
– Chapter 18 Networking
– Chapter 19 Java Data Structures
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•
•
•
•
•
Chapter 1
Objectives:
Get an overall perspective of what
capabilities and features are
encompassed by Java and its
development kit.
Take a first look at Java syntax.
Getting Input from Input Dialog
Boxes
Style and Documentation Guidelines
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What Is Java?
• History
• Characteristics of Java
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What is Java?
• An Object-Oriented Programming Language
developed at Sun Microsystems
• A Virtual Machine (run-time environment) that
can be embedded in web browsers (e.g.
Netscape Navigator, Microsoft Internet
Explorer and IBM WebExplorer) and operating
systems.
• A set of standardized Class libraries
(packages), that support:
– Creating graphical user interfaces
– Communicating over networks
– Controlling multimedia data
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History
• James Gosling and Sun Microsystems
• Oak
• Java, May 20, 1995, Sun World
• HotJava
– The first Java-enabled Web browser
• JDK Evolutions
• J2SE, J2ME, and J2EE (not mentioned
in the book)
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Characteristics of Java
•
•
•
•
•
Java is simple
Object-Oriented
Distributed
Interpreted
Robust
• Secure
• Architectureneutral
• Portable
• High-performance
• Multithreaded
• dynamic
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Java is Simple
• Java is not just a language for use
with the Internet.
• It is a full featured Object-Oriented
Programming Language (OOPL).
• Java is a bit easier than the popular
OOP language C++.
• Java uses automatic memory
allocation and garbage collection.
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What is Object-Oriented
Programming?
• Think of OOP as a set of
implementation techniques that
– Can be done in any programming language
– Are very difficult to do in most
programming languages
– OOP provides great flexibility,
modularity, and reusability.
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Java is Distributed
• Distributed computing involves
several computers working together
on a network.
• Java’s concurrency features make is
unique for developing many
interactive and networked
applications.
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Java is Interpreted
• Java Virtual Machine:
– Java is compiled to byte-codes whose
target architecture is the Java Virtual
machine (JVM).
– The virtual machine is embeddable within
other environments, e.g. web browser
and operating systems.
– Utilize a byte-code verifier when
reading in byte-codes. The class loader
is employed for “classes” loaded over the
network (enhances security)
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Java Virtual Machine
• JVM
Environment
Java Source code javac Java byte-code
.java
.class
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java
Java VM
Java is Robust
• Robust means reliable.
• No programming language can ensure complete
reliability.
• Java puts a lot of emphasis on early checking
for possible errors, because Java compilers can
detect many problems that would first show up
at execution time in other languages.
• Java has a runtime exception-handling feature
to provide programming support for
robustness.
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Java Is Architecture-Neutral
• Java is interpreted.
• JIT compiler
– Just-in-time compilers
– This provides
• Improved performance
• Better match to specific hardware
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JIT Compiler
• JIT- takes byte-codes and change it
to machine code.
JVM
Running
Applet or Application
.class file
machine code
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J.I.T.
Compiler
JIT Compiler
• Because of the need for architecture
independence, performance tuning must be
performed on the client-side.
• This client-side compilation is known as
Just-In-Time (JIT) compilation.
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Portable, Dynamic, Multithreaded,
and Extensible
• Java runtime based on architecturally-neutral byte-codes
(per class).
• Multithreading is a program’s capability to perform several
tasks simultaneously.
Java
Runtime
interpreted
call
Native
.dll
Native
.dll
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loaded
classes
(byte-codes)
.class
files
Advantages
• Byte-code is a compact machine
language form. In Java the target
machine is the Java Virtual Machine
(VM).
• These byte-codes are thus portable
across architecture boundaries.
• Applets and Applications have “class”
files loaded on their behalf in order to
execute.
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JDK Versions
•
•
•
•
•
JDK 1.02 (1995)
JDK 1.1 (1996)
Java 2 SDK v 1.2 (a.k.a JDK 1.2, 1998)
Java 2 SDK v 1.3 (a.k.a JDK 1.3, 2000)
Java 2 SDK v 1.4 (a.k.a JDK 1.4, 2002)
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JDK Editions
• Java Standard Edition (J2SE)
– J2SE can be used to develop client-side standalone
applications or applets.
• Java Enterprise Edition (J2EE)
– J2EE can be used to develop server-side applications
such as Java servlets and Java ServerPages.
• Java Micro Edition (J2ME).
– J2ME can be used to develop applications for mobile
devices such as cell phones.
This book uses J2SE to introduce Java
programming.
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Java IDE Tools
• Forte by Sun MicroSystems
• Borland JBuilder
• Microsoft Visual J++
• WebGain Café
• IBM Visual Age for Java
• IBM Eclipse
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Getting Started with Java
Programming
• A Simple Java Application
• Compiling Programs
• Executing Applications
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Example 1.1
Command Line
//This application program prints Welcome
//to Java!
package chapter1;
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!");
}
}
Source
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Run
Creating and Compiling Programs
Create/Modify Source Code
Source Code
• On command line
– javac file.java
Compile Source Code
i.e. javac Welcome.java
If compilation errors
Bytecode
Run Byteode
i.e. java Welcome
Result
If runtime errors or incorrect result
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Executing Applications
• On command line
– java classname
Bytecode
Java
Interpreter
on Windows
Java
Interpreter
on Linux
...
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Java
Interpreter
on Sun Solaris
Command line Example
javac Welcome.java
java Welcome
output:...
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Compiling and Running a Program
Welcome.java
c:\example
chapter1
Welcome.class
Welcome.java~
.
.
.
Where are the files
stored in the
directory?
chapter2
Java source files and class files for Chapter 2
chapter19
Java source files and class files for Chapter 19
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There are three forms of comments in Java.
1-int i = 10; // i is used as a counter
2The multiline comment
/* This is a comment */
This form of comment may also extend
over several lines as shown here:
/*
This is a longer comment
that extends over
five lines.
*/
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There are three forms of comments in Java.
3- This is the documentation comment.
/**
This is a Java
documentation
comment
*/
The advantage of documentation comments is
that tools can extract them from source files
and automatically generate documentation for
your programs. The JDK has a tool named
javadoc that performs this function.
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Package
•The second line in the program (package
chapter1;) specifies a package name, chapter1, for
the class Welcome.
•Forte compiles the source code in Welcome.java,
generates Welcome.class, and stores
Welcome.class in the chapter1 folder.
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Blocks
A pair of braces in a program
forms a block that groups
components of a program.
public class Test {
public static void main(String[] args) {
System.out.println("Welcome to Java!");
}
}
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Class block
Method block
Block Styles
Use end-of-line style for braces.
Next-line
style
public class Test
{
public static void main(String[] args)
{
System.out.println("Block Styles");
}
}
public class Test {
public static void main(String[] args) {
System.out.println("Block Styles");
}
}
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End-of-line
style
main Method
The main method provides the control
of program flow. The Java
interpreter executes the application
by invoking the main method.
The main method looks like this:
public static void main(String[]
args) {
// Statements;
}
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Displaying Text in a Message Dialog Box
• you can use the showMessageDialog
method in the JOptionPane class.
• JOptionPane is one of the many
predefined classes in the Java
system, which can be reused.
Source
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Run
The showMessageDialog Method
JOptionPane.showMessageDialog(null, "Welcome
to Java!",
"Example 1.2",
JOptionPane.INFORMATION_MESSAGE));
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import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
import java.awt.Graphics;
/*
*/
A simple Java
Applet
<applet code="FirstApplet" width=200 height=200>
</applet>
public class FirstApplet extends Applet
{
public void paint(Graphics g)
{
g.drawString("This is my first applet!", 20, 100);
}
}
See word doc for output.
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Integral Literals
• Integral literals may be expressed in
decimal, octal, or hexadecimal.
• The default is decimal.
• To indicate octal, prefix the literal with 0
(zero)
• To indicate hexadecimal, prefix the literal
with 0x or 0X;
• the hex digits may be upper-or lowercase.
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Integral Literals
For example:
The value twenty-eight may be expressed
the following ways:
28
034
0x1c
0x1C
0X1c
0X1C
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Integral Literals
• By default, an integral literal is a 32-bit
value.
• To indicate a long (64-bit) literal, append
the suffix L to the literal expression.
• The suffix can be lowercase, but then it
looks so much like a one that makes it
confusing.
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Literals
• Literals are explicit data values that appear in
your program.
• A literal is a value specified in the program
source, as opposed to one determined at
runtime. Literals can represent primitive or
string variables, and may appear on the right
side of assignments or in method calls. You
cannot assign a value into a literal, so they
cannot appear on the left of an assignment.
For example:
int x = 25;
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Boolean Literals
• The only literals of boolean type are
true and false.
For example:
1. boolean isBig = true;
2.
boolean isLittle = false;
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char Literals
A char literal can be expressed by
enclosing the desired character
in single quotes,
For example:
char c = ' w ';
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Chapter 1 Topic Summary
• Java is many things
– A concurrent object-oriented
programming language
– A virtual machine and Web-aware runtime
– A powerful and stable set of class
libraries.
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Chapter 2
Liang, Nutshell
Objectives:
• Introduce Programming with an Example
• Identifiers, Variables, and Constants
• Primitive Data Types
– byte, short, int, long, float, double, char,
boolean
• Expressions
• Operators, Precedence, Associativity, Operand
Evaluation Order: ++, --, *, /, %, +=, -=, *=,
/=, %=, ^, &, |, +, -,
• Syntax Errors, Runtime Errors, and Logic
ErrorsLiang, Oreilly, Herbert Schildt, Joseph O’Neil
Java Reserved Words
or Keywords
•
•
•
•
•
•
•
•
•
•
abstract
boolean
break
byte
case
catch
char
class
const
continue
default
do
double
else
extends
final
finally
float
for
goto
if
implements
import
instanceof
int
interface
long
native
new
package
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private
protected
public
return
short
static
strictfp
super
switch
synchronized
this
throw
throws
transient
try
void
volatile
while
Keyword and identifiers
• An identifier is a word used by a
programmer to name a variable, method,
class, or label.
• Keywords and reserved words may not be
used as identifiers.
• An identifier must begin with a letter, a
dollar sign (4), or an underscore (_);
subsequent characters may be letter,
dollar signs, underscores, or digits.
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• foobar
Examples
// legal
• BIGinterface
// legal
• $incomeAfterExpenses
// legal
• 3_nodes5
// illegal
• !theCase
// illegal
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Using Keyword
• Using a keyword as an
identifier is a syntax error
• Keywords that are reserved,
but not used, by Java
– const
– goto
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Reserved Words
•Reserved words or keywords are words that have a
specific meaning to the compiler and cannot be
used for other purposes in the program.
•For example, when the compiler sees the word
class, it understands that the word after class is
the name for the class.
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Java support eight different basic data type
• Type
•
•
•
•
•
•
•
•
character
boolean
byte
short
integer
long
float
double
Description
16-bit Unicode character data
true/false values
8-bit signed integer numbers
16-bit signed integer numbers
32-bit signed integer numbers
64-bit signed integer numbers
32-bit signed floating-point numbers
64-bit signed floating-point numbers
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Keyword
char
boolean
byte
short
int
long
float
double
Primitive Data Type
• Java's Primitive
data type
boolean
char
byte
short
int
long
float
double
C++ Simple data type
integral
floating
char
float
short
long
int
long double
long
enum
unsigned char
unsigned short
unsigned int
unsigned long
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Primitive Data Types and
Operations
• Type
Precision
byte
short
int*
long
char
float
double
boolean
‘obj-ref’
8 bits
16 bits
32 bits
64 bits
16 bits
32 bits
64 bits
-
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Default Value
0
0
0
0
\u0000
+0.0f
+0.0d
false
null
The four signed data types are:
v
v
v
v
byte
short
int
long
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Valid Control Character
• Valid control character are:
– \b
backspace
– \t
horizontal tab
– \n
linefeed
– \f
formfeed
– \r
carriage return
– \”
double quote
– \’
single quote
– \\
backslash
– “dddd”
for Unicode - is 0000 to hex
ffff
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•
•
•
•
•
•
•
•
•
•
•
•
•
•
Operator Precedence
var++, var-+, - (Unary plus and minus), ++var,--var
(type) Casting
! (Not)
*, /, % (Multiplication, division, and modulus)
+, - (Binary addition and subtraction)
<, <=, >, >= (Comparison or Relational)
==, !=; (Equality)
& (Unconditional AND)
^ (Exclusive OR)
| (Unconditional OR)
&& (Conditional AND) Short-circuit AND
|| (Conditional OR) Short-circuit OR
=, +=, -=, *=, /=, %= (Assignment operator)
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Bitwise Operators
Java defines several bitwise operators
which can be applied to the integer
types,
long, int, short, char, byte
These operators act upon the individual
bits of their operands.
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Bitwise Operators
Operator
~
&
|
^
>>
>>>
<<
Name
Bitwise unary NOT
Bitwise AND
Bitwise OR
Bitwise exclusive OR
Shift right
Shift right zero fill
Shift left
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Bitwise Operators
Operator
&=
|=
^=
>>=
>>>=
<<=
Name
Bitwise AND assignment
Bitwise OR assignment
Bitwise exclusive OR assignment
Shift right assignment
Shift right zero fill assignment
Shift left assignment
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Bitwise NOT ( ~)
• Also called the bitwise complement, the
unary NOT operator, ~ ,
• Inverts all the bits of its operand.
• Example
Number
74
before bitwise NOT
->
01001010
after the NOT operator applied -> 10110101
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Bitwise AND ( & )
• Produces a 1 bit if both operands are also
1, otherwise a zero is produced.
Example
Number
74 & 29 -> 8
->
01001010
-> &
00011101
After ->
0 0 0 0 1 000
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Bitwise OR ( | )
• Combines bits such that if either of the
bits in the operands is a 1, then the
resultant bit is a 1. A zero if both bits are
zeros.
Example
Number
74 | 29 -> 95
->
01001010
-> |
00011101
After ->
01 011111
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Bitwise XOR ( ^ )
• Combines bits such that if exactly one
operand is 1, then the result is 1.
Otherwise, the result is zero.
Example
Number
74 | 29 -> 87
->
01001010
-> ^
00011101
After ->
01 010111
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Left shift ( << )
Right shift ( >> )
unsigned right shift ( >>>)
• Left shift (>>) shifts all of the bits in a value to
the left a specified number of times.
• Right shift (>>) shifts all of the bits in a value
to the right a specified number of times.
• Unsigned right shift (>>>) automatically fills the
high-order bits with its previous contents each
time a shift occurs. This preserves the sign of
the value.
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Relational or Comparisons Operators
Operator
==
!=
>
<
>=
<=
Name
Equal to
Not equal to
Greater than
Less than
Greater than or equal to
Less than or equal to
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Relational Operators
The relational operators determine the
relationship that one operand has to
the other
They determine equality and ordering.
The result of these operations is a
boolean value.
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Boolean Logical Operators
Operator
&
|
^
||
&&
!
Name
Logical AND
Logical OR
Logical XOR (exclusive OR)
Short-circuit OR
Short-circuit AND
Logical unary NOT (inverts)
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Boolean Logical Operators
Operator
&=
|=
^=
==
!=
?:
Name
AND assignment
OR assignment
XOR assignment
Equal to
Not equal to
Ternary if-then-else
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Boolean Logical Operators
The Boolean Logical operators operate
only on boolean operands.
All of the binary logical operators
combine two boolean values to form a
resultant boolean value.
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The boolean Type and Operators
boolean lightsOn = true;
boolean lightsOn = false;
boolean b = (1 > 2);
&& (and)
• || (or)
•!
(not)
(1 < x) && (x < 100)
(lightsOn) || (isDayTime)
!(isStopped)
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Truth Table for Operator !
Truth Table for Operator !
Operand
!Operand
true
false
false
true
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Truth Table for Operator &&
Operand1Operand2Operand1 &&
Operand2
false
false
false
false
true
false
true
false
false
true
true
true
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Truth Table for Operator ||
Operand1 Operand2 Operand1 ||
Operand2
false
false
false
false
true
true
true
false
true
true
true
true
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Truth Table for Operator ^
Operand1 Operand2 Operand1 ^
Operand2
false
false
false
false
true
true
true
false
true
true
true
false
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The & and | Operators
&&: conditional AND operator
&: unconditional AND operator
||: conditional OR operator
|: unconditional OR operator
exp1 && exp2
(1 < x) && (x < 100)
(1 < x) & (x < 100)
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The & and | Operators
If x is 1, what is x after this
expression?
(x > 1) & (x++ < 10)
If x is 1, what is x after this
expression?
(1 > x) && ( 1 > x++)
How about (1 == x) | (10 > x++)?
(1 == x) || (10 > x++)?
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Getting Input from Input Dialog Boxes
String string = JOptionPane.showInputDialog(
null, “Prompt Message”, “Dialog Title”,
JOptionPane.QUESTION_MESSAGE));
where x is a string for the prompting message
and y is a string for the title of the input
dialog box.
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Convertting Strings to Doubles
To convert a string into a double
value, you can use the static
parseDouble method in the Double class
as follows:
double doubleValue
=Double.parseDouble(doubleString);
where doubleString is a numeric string
such as “123.45”.
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Read / Work With (Course Links)
•
•
•
•
Liang, Nutshell Chapter 3-4
Life Cycle of Applets
List Of Basic Tags
Try It Editor
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Chapter 3
Control Statements
•Selection Statements
–Using if and if...else
–Nested if Statements
–Using switch Statements
–Conditional Operator
•Repetition Statements
–Looping: while, do-while, and for
–Nested loops
–Using break and continue
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Selection Statements
• if Statements
• switch Statements
• Conditional Operators
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Caution
Adding a semicolon at the end of an if
clause is a common mistake.
if (radius >= 0);
Wrong
{
area = radius*radius*PI;
System.out.println(
"The area for the circle of radius " +
radius + " is " + area);
}
This mistake is hard to find, because it is
not a compilation error or a runtime error,
it is a logic error.
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switch Statements
switch (year) {
case 7: annualInterestRate = 7.25;
break;
case 15: annualInterestRate = 8.50;
break;
case 30: annualInterestRate = 9.0;
break;
default: System.out.println(
"Wrong number of years, enter 7,
15, or 30");
}
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Repetitions
• while Loops
• do-while Loops
• for Loops
• break and continue
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
• Introducing Methods
Chapter 4
Methods
– Benefits of methods, Declaring Methods, and
Calling Methods
• Passing Parameters
– Pass by Value
• Overloading Methods
– Ambiguous Invocation
• Scope of Local Variables
• Method Abstraction
• The Math Class
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Introducing Methods
A method is a
collection of
statements that are
grouped together
to perform an
operation.
Method Structure
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Methods
• A method is essentially a set of program
statements. It forms the fundamental unit
of execution in Java. Each method exists
as part of a class.
During the execution of a program,
methods may invoke other methods in the
same or a different class.
No program code can exist outside a
method, and no method can exist outside a
class.
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Using Methods
For example:
public class TheMethod
{
public static void main(String[] args)
{
System.out.println(“First method”);
}
}
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All methods are passed by value.
• All methods are passed by value. This
means that copies of the arguments are
provided to a method.
• Any changes to those copies are not visible
outside the method.
• This situation changes when an array or
object is passed as an argument.
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
call-by-value argument passing
• In this case the entire array or object is
not actually copied.
• Instead, only a copy of the reference is
provided.
• Therefore, any changes to the array or
object are visible outside the method.
• However, the reference itself is passed by
value.
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
call-by-value argument passing
•
•
•
•
Method a( ) accepts three arguments:
an int
an int array
an object reference
The value of these arguments are
displayed before and after the
method call.
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
call-by-value argument passing
• The key points to note are:
• The change to the first argument is
not visible to the main( ) method.
• The changes to the array and object
are visible to the main( ) method.
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
public class CallByValue
{
public static void main(String[] args)
{
// Initializes variables
int i = 5;
int j[] = { 1, 2, 3, 4, };
StringBuffer sb = new StringBuffer("abcd");
// Display variables
display(i, j, sb);
// call method
a(i, j, sb);
}
//Display variables again
display(i, j, sb);
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Example:
Example (con’t)
}
public static void a(int i, int j[], StringBuffer sb)
{
i = 7;
j[0] =11;
sb.append("fghi");
}
public static void display(int i, int j[], StringBuffer sb)
{
System.out.println(i);
for (int index = 0; index < j.length; index++)
System.out.print(j[index] + " ");
System.out.println(" ");
System.out.println(sb);
}
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Methods that return Values.
The return type for a method can be used
in the Java
• The return type for a method can be any
type used in the Java programming
language, which includes the primitive (or
scalar) types int, double, char, and so on, as
well as class type (including class types you
create).
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Methods that return values
public class GettingARaise
{
public static void main(String[] args)
{
double mySalary = 200.00;
System.out.println("Demonstrating some raises");
}
predictRaise(mySalary);
System.out.println("Demonstrating my salary " + mySalary);
predictRaise(400.00);
predictRaiseGivenIncrease(600, 800);
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Methods that return values
public static void predictRaise(double moneyAmount)
{
double newAmount;
newAmount = moneyAmount * 1.10;
System.out.println("With raise salary is " +
newAmount);
}
}
public static void predictRaiseGivenIncrease(double moneyAmount, double
percentRate)
{
double newAmount;
newAmount = moneyAmount * (1 + percentRate);
System.out.println("With raise predicted given salary is
" + newAmount);
}
Liang, Oreilly, Herbert Schildt, Joseph O’Neil
Read / Work With (Course Links)
•
•
•
•
Liang, Nutshell Chapter 4-6
Life Cycle of Applets
List Of Basic Tags
Try It Editor
Liang, Oreilly, Herbert Schildt, Joseph O’Neil