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Algorithm Programming 1 (using Java) 89-210

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

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Algorithm Programming 1 (using Java) 89-210

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  1. Algorithm Programming 1(using Java) 89-210 Bar-Ilan University 2007-2008 תשס"ח by Moshe Fresko

  2. Course objectives • Learning Professional Programming • by Algorithmic Examples • Learning Java • Object Oriented Programming • Design Patterns • Multithreaded Programming • GUI • Run-time Class Information

  3. 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 %

  4. 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

  5. History • Early 1990s, Oak, by Sun • For embedded systems in Consumer Electronic Devices • 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) • With HotJava capable of running Applets • 1998, Sun released Java 2 SDK (J2SDK) • By time Bunch of Libraries are added

  6. Object Oriented Reminders • Abstraction • Encapsulation • Inheritance • Abstract classes • Polymorphism • By Inheritance • By Overloading • Interfacing • Constructors and Finalizers

  7. 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)

  8. 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 SoftwareRussel Winder & Graham Roberts 2nd Edition, 2000 John Wiley and Sons, Ltd. • Java 2 CompleteGemma O’Sullivan1998, Sybex • Thinking in JavaBruce Eckel 3rd Edition (free to download) • Design PatternsErich Gamma, Richard Helm, Ralph Johnson, John Vlissides1995, Addison Wesley • Other Java Books …

  9. 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

  10. 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!"); } }

  11. 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.

  12. 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>

  13. JVM • Source Code • Java Compiler (javac) -> ByteCode • Java Interpreter (java) - Java VM

  14. Class Class Class Class Execution Engine JNI Adapter Interface Adapter OS 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

  15. Java Bytecode • Like C++ Assembly, JavaByteCode • We need to check ByteCode • For Performance and Memory Usage Tuning • Size and Execution Speed • Debugging

  16. 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 creates Employee.class javap –c Employee to print to string the byte-code in visual form

  17. Java Bytecode - Example 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 } 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

  18. Java Bytecode - opcodes • opcodes • a... : opcode is manipulating type object ref. • i… : opcode is manipulation type integer • b… : byte, • c... : char, • d… : double, etc.

  19. 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

  20. Java Bytecode – JVM diagram

  21. Java Bytecode • Local variables • 0th : this (for constructors or instant methods) • Then parameters • Then local variables • Operand stack • 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

  22. 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

  23. 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

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