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SOFTWARE AND PROGRAMMING 1. EACH student must have obtained access to Birkbeck computing by 26.01.11 – otherwise no use in the lab Instructor: Prof. Boris Mirkin DCSIS, room 744 MAL, tel. 020 7631 6746 E-mail: Course Assistant:

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software and programming 1


EACH student must have obtained access

to Birkbeck computing by 26.01.11 – otherwise no use in the lab

Instructor: Prof. Boris Mirkin

DCSIS, room 744 MAL, tel. 020 7631 6746


Course Assistant:

Lab/WebCT/Tests/Assignments: Mr Martin O’Shea


(FROM 26 January: Lectures 6.00-7.30, Labs 7.30-9.00)


The course web page is currently at my open web-site, with lecture notes and other relevant materials:

texts any including
Texts: Any, including
  • Quentin Charatan & Aaron Kans [CK]
      • JAVA in Two Semesters, 2nd Edition, McGraw-Hill, 2006, ISBN-10 0077108892
  • David J. Barnes & Michael Kölling [BK]Objects First with Java: A Practical Introduction using BlueJ, 2nd edition, Pearson Education, 2005, ISBN 0-13-124933-9
  • The publisher supplies a helpline in installing related software
  • 3. I. Pohl, C. McDowell [PM]
  • Java by dissection, Addison-Wesley, 2000, ISBN 0201751585
  • 4.J. Farrell [F]
  • Java Programming, 2-4 editions, Course Technology, Thompson, 2003-7, ISBN 0-619-21500-3 etc.
  • 5. Free: ON-LINE text by D. Eck (on my web site); other URLs
teaching goal coding in real
Teaching Goal: Coding in Real


  • the interpreter/compiler Java working;
  • classes, objects and instances;
  • variables and static variables;
  • Java data types: primitive and user-defined;
  • arithmetic and Boolean expressions;
  • for/while and if…elseif…else structures;
  • processing strings;
  • elements of input/output in Java;
  • methods and constructors;
  • arrays and their usage, including arrays of a user-defined type
teaching goal
Teaching Goal


To have developed skills in practical programming of small but real-world problems e.g. keeping transaction records,

assigning seats to customers,

managing a bus schedule, etc.

  • Final exam: 75% of mark
  • Course-work: 25% of mark
    • 2 open-book in-class tests, 9.02 & 9.03,
    • 2 assignments for home work via WebCT, 9.02-9.03 & 23.02-23.03

Composition of CW 25% mark:

T1 5%

T2 7%

A1 5%

A2 8%

control example
Control: Example
  • Let marks of a student be as follows:
    • Exam: 50
    • T1 12
    • T2 65
    • A1 100
    • A2 0 (hasn’t submitted)
  • The total mark will be 48 because it rounds up the result:

50*0.75 + 12*0.05 + 65*0.07 + 100*0.05 + 0*0.08=

=37.5 + 0.6 + 4.55 + 5 + 0 = 47.65

teaching philosophy extracts
Teaching Philosophy (extracts)
  • Hugerespect for part-time students
  • The bulk of students to get trained
  • No student’s question is stupid sinceSoftware is invented
  • Better to have simple things learnt well rather than complex things learnt not well
  • Instructor’s small errors - a good teaching device for activation of the student’s brain
  • Learning a language in a college differs from consuming a lunch in a diner in many ways
  • Fast feedback on students’ issues if raised
oop concepts you already know of
OOP concepts you already know of
  • How a Java program works: interpret/compile
  • Variable
  • Expression
  • Data type
  • Loop
  • If/elseif/else structure
  • Class
  • Method
  • Parameter

These will be expanded to more realistic environments

two java environments
Will be using both:

Java Developer Kit JDK (currently, J2SE) (Conventional)

Blue J (A public project to make JAVA coding easier)

Two JAVA environments
conventional jdk editing
A source code can be edited in any text editor: Notepad, emacs, PFE, ...

MS Wordcaveat: by default, Word does not save in ASCII text format

Make sure to save the code before compiling! The file name: the same as that of the class, with extension:

say, class NicTe{…} must be saved as file, case sensitive

Conventional JDK: Editing
command line invocation
compilation and execution of Java in JDK are done from a command line

On Microsoft systems: DOS shell

On Unix: Unix shell

Must make sure that the commands for compiler and runtime (JVM) are in the command path.

Command line invocation
getting jdk on a system s path
Getting JDK on a system’s path
  • Click “Properties” on right-buttoned “My computer”
  • Click “Advanced”
  • Click “Environmental variables”
  • Enter new path (to the directory in which javac.exe and java.exe reside)
compiling with jdk
Name of the JDK compiler: javac

To invoke:javac <source name>

compiles <source name> and all classes it depends on into an executable on JVM file <source name>.class

Example: javac

produces file NicTe.class

Compiling with JDK
execution in jdk
“java” starts the Java virtual machine:

java NicTe

The named class is loaded and execution is started.

Other classes are loaded as needed.

Only possible if class has been compiled into a file, say, NicTe.class

Execution in JDK
main method in jdk
BlueJ executes what the user says;

The JDK java system always executes a method called main, it should have a certain signature:


_______________________public static void main(String[ ] args){ ...}

To work with JDK, such a method must be present in your program!

“main” method in JDK
a primer program class
A primer program (=class)


Purpose: printing a message to the screen


class HelloWorld {

// Each program is organised as a class

public static void main(String[] args) {

         System.out.println("Hello World!");


} // end of class HelloWorld

/* Always Three Types of Elements ONLY:


-class (with modifiers)

-methods (with modifiers & parameters/arguments) */

bluej coding
BlueJ coding
  • BlueJ programs are organised in the so-called projects
  • A BlueJ project is stored in a project-specific directory on disk
  • Some files store the source code, some store the compiled code, some store additional BlueJ related information.
the bluej directory structure
The BlueJ directory structure


project: calculator












the bluej file structure
The BlueJ file structure
  • bluej.pkg - the package file. Contains information about classes in the package. One per package.
  • bluej.pkh - backup of the package file.
  • *.java - standard Java source file (text). One per class.
  • *.class - standard Java code file. One per class
  • *.ctxt - BlueJ context file. Contains extra information for a class. One per class.
software is free
Software is free
  • Available on BBK’s network
    • Java JDK (which allows you to compile and execute your program)
    • BlueJ (Preferred editor)
  • Installing BlueJ (for home use)
    • First download the Java JDK from
    • Then download BlueJ from
    • Run “bluejsetup-202.exe” and follow the given instructions
objects and classes
Objects and classes
  • Classes: program templates
    • represent all objects of a kind (example: “student”)
  • Objects === instances
    • A template copy to represent a specific element of the class (“an individual student”)
    • Instances are created with the so-called constructors, explicitly in JDK or somewhat easier in BlueJ
variables methods and parameters
Variables, methods and parameters
  • classescontain data stored in the so-called variables and operations which can be invoked (they are called methodsin Java)
  • methods may have inputs (they are called parameters in Java) to get additional data needed to have them executed
  • Many instances can be created from a single class
  • An object has attributes/variables: values stored in fields (memory locations).
  • The class defines what fields any its object has (a template), but each object may store its own set of values (the state of the object)
  • A variable is initialised with assigning it a value, an object – with a constructor
more on method
More on Method

Method in Java is a named set of instructions that transforms some input into an output. This is, actually, a machine implementation of the concept of algorithm which itself is a computational analogue to the mathematical concept of function.

Static method: is shared by all instances.

example of a method 1
Example of a method (1)

Square function y = x2

x               y

1                1

2                4

5               25

11            121

The table can be used for invoking a specific value, like, 72 = 49 or 102 = 100.

example of a method 2
Example of a method (2)

A Java method to calculate the square function:

public int sq(int x){

return xx;}

To make it work, variables are needed:

int sevs=sq(7); //puts 49 into sevs

int tens=sq(10);// puts 100 into tens

structure of a method
Structure of a method

Output’s type


modifiers return-type name ( parameter-list )



return variable/expression;

//if return type is not void



  • static -       method/variable that belongs to class as whole and is shared by all instances
  • public -    method/variable that is accessible from anywhere
  • private -    method/variable that is accessible from only within the class
helloworld with a method
HelloWorld with a method

// Hello-world program to demonstrate BlueJ

class Hello{

// Method that does the work of printing

public void go()

{ System.out.println("Hello, world");


// main method for working outside BlueJ

public static void main(String[] args)

{ Hello hi = new Hello(); //instance

hi.go(); //method in instance hi



helloworld why
HelloWorld : WHY

Why dots in

System.out.println("Hello, world");



  • To take method from a specific class instance
  • To take a class from a set of classes: Java is organised as a hierarchically structured set of classes in individual files
assigning values
Assigning values
  • Values are stored into fields (and other variables) via assignment statements:
    • variable = expression;
    • price = ticketCost;
  • The value on the right is assigned to a variable on the left.
  • A variable stores a single value, so any previous value is lost.
  • It provides for multiple uses of the same program
  • A variable is a name for a location in memory that can hold data.
  • Variables are declared and/or initialisedA variable declaration includes the following:
    • A data type that identifies the type of data that is stored in the variable
    • An identifier that is the variable’s name
    • An optional assigned initial value

In memory:

int p;

p = 4;



scope of a variable
Scope of a variable:

The range of statements that can access the variable.

It stretches from the declaration point to the end of the block containing the declaration

Q: WHAT is BLOCK ? (part within curly braces{…} )

Q: WHAT is DECLARATION? (type name ; 3-part command)

helloworld n times bluej
HelloWorld N times BlueJ

public class HelloN {

int number; \\ variable declared

public void go()

{ System.out.println("Hello, world"); }

public HelloN(int howmany)

{number=howmany; } \\constr to initialise object

public void prrt() \\printing number times

{ for(int i=1;i<=number;i++) \\loop


System.out.println("ok"); } }

loop for
Loop for

for(int var=1;var<=st;var++){do operation depending on var}

  • Two types of parentheses: () and {}
  • The expression in () consists of three different items: initialising a variable,variable update, and stop-condition
  • Given a value of var, {} is executed, after which varis updated, then stop-condition checked and, if yes, {} is executed again; if no, the program proceeds further on
no in for loop in hellon
No { } in for-loop in HelloN


Let us add { }: where?

Is there any difference

between before and after “ok”?

arithmetic expressions
Arithmetic Expressions
  • 2 * 6 / 4 + 5 – 2 * 3 = 3 + 5 – 6 = 2
  • 2 * 6.0 / (4 + 5) – 2 * 3 = 12.0/9 – 6 = – 4.67 (note: reals, not integers)
  • 2 * 6 / 4 + (5 – 2) * 3 = 12

Java uses a natural precedence structure of arithmetic operations. If you are not sure, use parentheses!!!

basic class structure
Basic class structure

The outer wrapper

of TicketMachine

public class TicketMachine


Inner part of the class omitted.


public class ClassName






The contents of a


concepts considered overview
Concepts considered: overview
  • Compiler & interpreter
  • JDK/JDS and BlueJ environments
  • Method
  • Variable; declaration and intialisation
  • Primitive variable types
  • Class type
  • Arithmetic operators and expressions
  • Class and instance
  • HelloWorld class in three versions