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Algorithm Programming 1
(using Java)
89-210
Bar-Ilan University
2007-2008 תשס"ח
by Moshe Fresko
Course objectives
Learning Professional Programming
by Algorithmic Examples
Learning Java
Object Oriented Programming
Design Patterns
Multithreaded Programming
GUI
Run-time Class Information
Course Requirements
Exercises/Projects, 25 % of the grade
Programming Exercises
One step-by-step Project
Time schedules are strict, no late exercises are
accepted.
They will be handed on via the Department
Submitec utility
Cheating is punished by Discipline Assembly
( Very strictly )
Exam 75 %
What is Java ?
(Almost) Fully OO Programming Language.
Syntax: Similar to C++, Different in some
Semantics and Internals.
Architecture Neutral
World-Wide-Web programming language
History
Early 1990s, Oak, by Sun
1994, Sun decided to adapt Oak to Web
January 1995, renamed as Java,
Building Web based applications
May 1995, Sun’s first JDK (Java Development Kit)
For embedded systems in Consumer Electronic Devices
With HotJava capable of running Applets
1998, Sun released Java 2 SDK (J2SDK)
By time Bunch of Libraries are added
Object Oriented Reminders
Abstraction
Encapsulation
Inheritance
Abstract classes
Polymorphism
By Inheritance
By Overloading
Interfacing
Constructors and Finalizers
Design Patterns
Design Patterns help you learn from others’
successes, instead of your failures
Separate things that change, from the things
that doesn’t change
Elegant and Cheap-to-Maintain
Inheritance can be thought as a DP, and so
Composition, etc.
Iterator (Enumeration in Java 1.0 and 1.1)
Resources
Internet
http://java.sun.com
For Tutorials and Downloads
http://java.sun.com/j2se/1.4.2/docs/api/
API of Java 1.4
http://java.sun.com/j2se/1.5.0/docs/api/
API of Java 1.5
http://java.sun.com/docs/books/tutorial/reallybigindex.html
Development Environment
NetBeans ide
Symantec’s Cofe
Borland’s JBuilder
Books
Developing Java Software
Russel Winder & Graham Roberts
2nd Edition, 2000 John Wiley and Sons, Ltd.
Java 2 Complete
Gemma O’Sullivan
1998, Sybex
Thinking in Java
Bruce Eckel
3rd Edition (free to download)
Design Patterns
Erich Gamma, Richard Helm, Ralph Johnson, John Vlissides
1995, Addison Wesley
Other Java Books …
JDK, J2SE
J2SE, J2EE and J2ME
JFC : Java Foundation Classes
Java2D : 2D Graphics
JavaBeans : Java object component technology
Servlets : Web Server
JavaHelp : For creating help systems
etc.
javac : Compiler to Byte-Code
java : Loads a byte-code into JVM and executes
javap : Byte-code viewer
javadoc : Creates HTML documentation for the code.
jdb : Java debugger
appletviewer : To view applets from within an HMTL page
Application Example
Programs
Applications
Applets
Programs are Case Sensitive
Example: HelloWorldApp.java file
public class HelloWorldApp {
public static void main(String[] args) {
System.out.println("Hello World!");
}
}
Application Example
javac HelloWorldApp.java
Compiles and creates ByteCode in file
“HelloWorldApp.class”
java HelloWorldApp
Looks for the file “HelloWorldApp.class”
and for the class “HelloWorldApp” in it,
and starts to run the static “main” function.
Applet Example
// HelloWorld.java file
import java.applet.*;
import java.awt.*;
public class HelloWorld extends Applet {
public void paint(Graphics g) {
g.drawString("Hello world!", 50, 25);
}
}
// Hello.html file
<HTML>
<HEAD><TITLE>A Simple Program</TITLE></HEAD>
<BODY>Here is the output of my program:
<APPLET CODE="HelloWorld.class" WIDTH=150 HEIGHT=25></APPLET>
</BODY>
</HTML>
JVM
Source Code
Java Compiler (javac) -> ByteCode
Java Interpreter (java) - Java VM
JVM
java -classpath …;…;…
for providing paths of class libraries, and .jar files
.jar files are a set of class files compressed into a single file
Class
Class
Class
Execution Engine
JNI
Adapter Interface
Adapter
OS
Class
Java Bytecode
Like C++ Assembly, JavaByteCode
We need to check ByteCode
For Performance and Memory Usage Tuning
Size and Execution Speed
Debugging
Java Bytecode - Example
class Employee {
private String name ;
private int idNumber ;
public Employee(String strName, int num) {
name = strName ;
idNumber = num ;
storeData(strName,num) ;
}
public String employeeName() {
return name ;
}
public int employeeNumber() {
return idNumber ;
}
private void storeData(String s, int num) {
// ...
}
}
javac Employee.java
javap –c Employee
creates Employee.class
to print to string the byte-code in visual form
Java Bytecode - Example
Compiled from "Employee.java"
class Employee extends java.lang.Object{
public Employee(java.lang.String,int);
Code:
0:
aload_0
1:
invokespecial
#1;
//Method java/lang/Object."<init>":()V
4:
aload_0
5:
aload_1
6:
putfield
#2;
//Field name:Ljava/lang/String;
9:
aload_0
10: iload_2
11: putfield
#3;
//Field idNumber:I
14: aload_0
15: aload_1
16: iload_2
17: invokespecial
#4;
//MethodstoreData:(Ljava/lang/String;I)V
20: return
public java.lang.String employeeName();
Code:
0:
aload_0
1:
getfield
#2;
//Field name:Ljava/lang/String;
4:
areturn
public int employeeNumber();
Code:
0:
aload_0
1:
getfield
#3;
//Field idNumber:I
4:
ireturn
}
Java Bytecode - opcodes
opcodes
a... : opcode is manipulating type object ref.
i… : opcode is manipulation type integer
b… : byte,
c... : char,
d… : double, etc.
Java Bytecode - JVM
JVM
Stack-based machine
Each thread has a JVM stack which stores Frames
A frame is created each time a method is invoked
Each Frame has
Operand Stack
An array of Local variables
A reference to Runtime constant pool of the class of
the current method
Java Bytecode – JVM diagram
Java Bytecode
Local variables
Operand stack
0th : this (for constructors or instant methods)
Then parameters
Then local variables
LIFO stack, to pop and push values
Used to receive return values
Example
public string employeeName() { return name ; }
public java.lang.String employeeName();
Code:
0: aload_0
1: getfield
#2; //Field name:Ljava/lang/String;
4: areturn
aload_0 : pushes this pointer into stack
getfield #2 : this popped+2 added and get reference (for name) from runtime constant pool
of the class. This is loaded to the stack
areturn : returns the top value of the stack (name). It is popped from operand stack and
pushed to the operand stack of calling method
The real machine code is : 2A B4 00 02 B0
Java Bytecode
public Employee(String strName, int num) {
name = strName ;
idNumber = num ;
storeData(strName,num) ;
}
public Employee(java.lang.String,int);
Code:
0:
aload_0
1:
invokespecial
#1; //Method java/lang/Object."<init>":()V
4:
aload_0
5:
aload_1
6:
putfield
#2; //Field name:Ljava/lang/String;
9:
aload_0
10: iload_2
11: putfield
#3; //Field idNumber:I
14: aload_0
15: aload_1
16: iload_2
17: invokespecial
#4; //Method storeData:(Ljava/lang/String;I)V
20: return
String and StringBuffer
In package java.lang
StringBuffer is modifiable version of String class
String has
length
substring extraction
Finding and matching
String comparison
Uppercase and lowercase conversion
Leading and trailing whitespace elimination
Conversion to/from char arrays
Conversion from primitive types to String
Appending strings
Inserting strings
