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Advanced Programming

Advanced Programming

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Advanced Programming

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  1. Advanced Programming Rabie A. Ramadan Lecture 1

  2. Welcome Back

  3. Attendance is very important Assignments Projects Quizzes Class Organization

  4. Textbooks

  5. Object Serialization Advanced I/O - New I/O Reflection Advanced JDBC Networking with Sockets Remote Method Invocation Keys, Signatures, and Certificates Java Authentication and Authorization Service (JAAS) Parsing XML with Java - JAXP Java Design Patterns Effective Java topics Topics to be Covered

  6. Some presentations by myself Presentations by you Report discussion biweekly Labs Class Format

  7. Midterm grades will be added towards the project Labs Assignments Grading

  8. Introduction and Course Motivation Project Assignment 1 – Get your hands dirty Agenda

  9. Computer Programming is the art of making a computer do what you want it to do. Introduction and Course Motivation

  10. API – Application Programming Interface Classes, Interfaces, Constructors, Members, and Serialized Forms By Which a Programmer Accesses a Class, Interface, or Package User A Programmer Who Writes a Program That Uses an API Client A Class Whose Implementation Uses an API Terminology

  11. Focus on Clarity and Simplicity Don’t Surprise Users of an API Hide Complexity Underneath, Not In, The API Reuse Rather Than Copy Minimize Dependencies Between Modules Some Early Habits Need to Be Broken Detect Errors As Soon As Possible Compile-Time Detection Beats Run-Time Failure Run-Time Exceptions Beat Undefined Behavior Key Principles For Using Any Language

  12. Bloch Does not Focus on Performance Instead, Strive to Write Programs that are: Clear, Correct, Robust, Flexible, Maintainable Start With Sound Software Engineering Get Performance Later Where You Need It Excessive Performance Focus Has Real Costs Think About Why a Language Like C++ is so Complex Performance

  13. Just a coder Most of us are coders not programmers Programmer / Developer Writes an efficient code Who are You ?

  14. Project Project

  15. Available on the website Assignment 1

  16. Java is platform independent: the same program can run on any correctly implemented Java system Java is object-oriented: Structured in terms of classes, which group data with operations on that data Can construct new classes by extending existing ones Java designed as A core language plus A rich collection of commonly available packages Java can be embedded in Web pages Some Salient Characteristics of Java

  17. Begin with Java source code in text files: A Java source code compiler produces Java byte code Outputs one file per class:Model.class May be standalone or part of an IDE A Java Virtual Machine loads and executes class files May compile them to native code (e.g., x86) internally Java Processing and Execution Appendix A: Introduction to Java

  18. Compiling and Executing a Java Program Appendix A: Introduction to Java

  19. Click on link to Applet Byte code is downloaded Java: Write Once, Run Anywhere • Consequence of Java’s history: platform-independence Mac user running Safari Web page stored on Unix server Virtual machine translates byte code to native Mac code and the Applet is run Windows user running Internet Explorer Byte code (part of web page)

  20. Click on link to Applet Byte code is downloaded Java: Write Once, Run Anywhere • Consequence of Java’s history: platform-independent Mac user running Safari Web page stored on Unix server Windows user running Internet Explorer Virtual machine translates byte code to native Windows code and the Applet is run

  21. Dungeon Master (Java version) Kung Fu Panda 2: THQ Java: Write Once, Run Anywhere (2) • But Java can also create standard (non-web based) programs Examples of mobile Java games:

  22. Java: Write Once, Run Anywhere (3) • Java has been used by large and reputable companies to create serious stand-alone applications. • Example: • Eclipse1: started as a programming environment created by IBM for developing Java programs. The program Eclipse was itself written in Java. 1 For more information:

  23. Compiled Programs With Different Operating Systems UNIX compiler Executable (UNIX) Windows compiler Executable (Windows) Computer program Mac OS compiler Executable (Mac)

  24. Filename.class Java compiler (javac) Java program Java bytecode (generic binary) A High Level View Of Translating/Executing Java Programs Stage 1: Compilation

  25. Machine language instruction (UNIX) Filename.class Java interpreter (java) Machine language instruction (Windows) Java bytecode (generic binary) Machine language instruction (Apple) A High Level View Of Translating/Executing Java Programs (2) Stage 2: Interpreting and executing the byte code

  26. The class is the unit of programming A Java program is a collection of classes Each class definition (usually) in its own .java file The file name must match the class name A class describes objects (instances) Describes their common characteristics: is a blueprint Thus all the instances have these same characteristics These characteristics are: Data fields for each object Methods (operations) that do work on the objects Classes and Objects Appendix A: Introduction to Java

  27. API = Application Programming Interface Java = small core + extensive collection of packages A package consists of some related Java classes: Swing: a GUI (graphical user interface) package AWT: Application Window Toolkit (more GUI) util: utility data structures The import statement tells the compiler to make available classes and methods of another package A main method indicates where to begin executing a class (if it is designed to be run as a program) Grouping Classes: The Java API

  28. import javax.swing.*; // all classes from javax.swing public class HelloWorld { // starts a class public static void main (String[] args) { // starts a main method // in: array of String; out: none (void) } } public = can be seen from any package static = not “part of” an object ALittle Example of import and main

  29. javac Produces HelloWorld.class (byte code) javaHelloWorld Starts the JVM and runs the main method Processing and Running HelloWorld

  30. Java distinguishes two kinds of entities Primitive types Objects Primitive-type data is stored in primitive-type variables Reference variables store the address of an object References and Primitive Data Types

  31. Represent numbers, characters, boolean values Integers: byte, short, int, and long Real numbers: float and double Characters: char Primitive Data Types

  32. Primitive Data Types

  33. subscript [ ], call ( ), member access . pre/post-increment ++ --, boolean complement !, bitwise complement ~, unary + -, type cast (type), object creation new * / % binary + - (+ also concatenates strings) signed shift << >>, unsigned shift >>> comparison < <= > >=, class test instanceof equality comparison == != bitwise and & bitwise or| Operators

  34. logical (sequential) and && logical (sequential) or || conditional cond ? true-expr : false-expr assignment=, compound assignment += -= *= /= <<= >>= >>>= &= |= Operators

  35. Widening conversion: In operations on mixed-type operands, the numeric type of the smaller range is converted to the numeric type of the larger range In an assignment, a numeric type of smaller range can be assigned to a numeric type of larger range bytetoshorttointtolong intkind tofloattodouble Type Compatibility and Conversion

  36. int square; square = n * n; double cube = n * (double)square; Can generally declare local variables where they are initialized All variables get a safe initial value anyway (zero/null) Declaring and Setting Variables

  37. A group of statements executed in order is written { stmt1; stmt2; ...; stmtN; } The statements execute in the order 1, 2, ..., N Java Control Statements

  38. Java Control Statements (continued) Appendix A: Introduction to Java

  39. Java Control Statements (continued)

  40. A Java method defines a group of statements as performing a particular operation static indicates a static or class method A method that is not static is an instance method All method arguments are call-by-value Primitive type: value is passed to the method Method may modify local copy but will not affect caller’s value Object reference: address of objectis passed Change to reference variable does not affect caller But operations can affect the object, visible to caller Methods

  41. The String class defines a data type that is used to store a sequence of characters You cannot modify a String object If you attempt to do so, Java will create a new object that contains the modified character sequence TheStringClass Appendix A: Introduction to Java

  42. You can’t use the relational or equality operators to compare the values stored in strings (or other objects) (You will compare the pointers, not the objects!) ComparingObjects

  43. Stores character sequences Unlike a String object, you can change the contents of a StringBuffer object TheStringBufferClass Appendix A: Introduction to Java

  44. We often need to process individual pieces, or tokens, of a String StringTokenizerClass

  45. In Java, an array is also an object The elements are indexes and are referenced using the form arrayvar[subscript] Arrays

  46. float grades[] = new float[numStudents]; ... grades[student] = something; ... float total = 0.0; for (int i = 0; i < grades.length; ++i) { total += grades[i]; } System.out.printf(“Average = %6.2f%n”, total / numStudents); Array Example

  47. // possibly more efficient for (int i = grades.length; --i >= 0; ) { total += grades[i]; } // uses Java 5.0 “for each” looping for (float grade : grades) { total += grade; } Array Example Variations

  48. An InputStream is a sequence of characters representing program input data An OutputStream is a sequence of characters representing program output The console keyboard stream is The console window is associated with System.out Input/Output using Streams

  49. import*; public static void main (String[] args) { // open an input stream (**exceptions!) BufferedReader rdr = new BufferedReader( new FileReader(args[0])); // read a line of input String line = rdr.readLine(); // see if at end of file if (line == null) { ... } Opening and Using Files: Reading Input

  50. Item 1: Consider Static Factory Methods Instead of Constructors • Factory methods: • Have names, unlike constructors, which can clarify code. • Do not need to create a new object upon each invocation - objects can be cached and reused, if necessary. • Can return a subtype of their return type - in particular, can return an object whose implementation class is unknown to the caller.