SE 360Advances in Software

DevelopmentAsst.Prof.Dr. Senem Kumova Metin

Introduction

Instructor : Dr. Senem Kumova MetinEmail: senem.kumova@ieu.edu.trRoom: 312Course website: http://homes.ieu.edu.tr/skumova

You have to check website regularly for announcements, homeworks, course slides and projects

Assignments Labs and Project

• Starting next lecture, there will be 1 hour lab time. Bring your laptops!!!

• In the second part you will do a course project, in Java.

– Start thinking about your project now!!!– I leave the topic up to you.– Up to 2 people per group.

Syllabus

Classification of High level Programming languages

• Programming paradigm : Alternative approaches to the programming process

– Imperative (Procedural) (Fortran, Algol, Pascal, Basic, C)

– Functional (Lisp, ML)– Declarative(Logic) (Prolog,GPSS)– Object-Oriented (C++, Java, Scala, Smalltalk)

Programming Languages 1/2

• Imperative: The language provides statements, such as assignment statements , which explicitly change the state of the memory of the computer. X:=X+1

• Functional: In this paradigm we express computations as the evaluation of mathematical functions.

(defun factorial (n) (if (<= n 1)

1 (* n (factorial (- n 1)))))

The program can then be called as(factorial 10)

Programming Languages 2/2• Logic (Declarative): In this paradigm we express computation in

exclusively in terms of mathematical logic

brother(X,Y) /* X is the brother of Y */ :- /* if there are two people F and M for which*/ father(F,X), /* F is the father of X */ father(F,Y), /* and F is the father of Y */ mother(M,X), /* and M is the mother of X */ mother(M,Y), /* and M is the mother of Y */ male(X). /* and X is male */

uncle (X,Y)

:- father(F,Y), brother(X,F).

• Object-Oriented: In this paradigm we associate behavior with data-structures called " objects " which belong to classes which are usually structured into a hierarchy

What exactly is an object?

• An OBJECT is an identity which includes both Attributes and Behaviors

EXAMPLE -- > PERSON OBJECTAttributes : Eye Color, Age, Height …Behaviors : Walking, Talking, Breathing

…

The Object Model • A OO-software system is a set of cooperating

objects • Objects have state and processing ability • Objects exchange messages

Class and Object• A class is a collection of

objects that have common properties, operations and behaviors.

• A class is a data type, objects are instances of that data type.

Object Oriented Programming• A programming paradigm that uses abstraction (in the form of

classes and objects) to create models based on the real world environment.

• An object-oriented application uses a collection of objects, which

communicate by passing messages to request services.

• Objects are capable of passing messages, receiving messages, and processing data.

• The aim of object-oriented programming is to try to increase the flexibility and maintainability of programs. Because programs created using an OO language are modular, they can be easier to develop, and simpler to understand after development.

Java

• Main topic of the course is Object Oriented Concepts

• The implementation will be done in Java• You will learn Java, and use it in the project• I will use Eclipse as the Java IDE

– Free IDE, highly popular– Easy to use– The resource links are given in course web page

What is Java

• Java is a high level programming language

• Uses a virtual machine– Means your code is compiled for the VM andworks in any architecture or OS (byte code– Performance penalty due to VM instead of nativeapplications

• You can write applications or applets using Java Applet is a Java program that works on web pages.

Java: Write Once, Run Anywhere• Consequence of Java’s history:

platform-independence

Mac user running Safari

Windows user running Internet Explorer

Web page stored on Unix server

Click on link to Applet

Byte code is downloaded

Virtual machine translates byte code to

native Mac code and the Applet is run

Byte code (part of web page)

From slides of James Tam

Java: Write Once, Run Anywhere• Consequence of Java’s history:

platform-independent

Mac user running Safari

Windows user running Internet Explorer

Web page stored on Unix server

Click on link to AppletByte code is downloaded

Virtual machine translates byte code to

native Windows code and the Applet is runFrom slides of James Tam

What is Java

• If you are a C/C++ programmer, Java is easier to code– No pointers– Has a garbage collection mechanism– Built in security

• Java is object oriented

A short history for Java The invention of the microprocessor revolutionized computers

(from huge computers to smaller ones )

The next logical step for microprocessors was to have them run in intelligent consumer devices like cable TV switchboxes..

Sun Microsystems funded an internal research project “Green” to investigate this opportunity (~1991)

– Result: A programming language called “Oak” JAVA

Java versus Java ScriptJava (this is what you need to know for this course)

– A complete programming language developed by Sun– Can be used to develop either web based or stand-alone

software– Many pre-created code libraries available– For more complex and powerful programs

Java Script (not covered in this course)– A small language that’s mostly used for web-based applications

(run through a web browser like Internet Explorer, Firefox, Safari, Chrome)

– Good for programming simple special effects for your web page e.g., roll-overs

– e.g.,

A High Level View Of Translating/Executing Java Programs

Java compiler (javac)

Java program

Filename.java

Java bytecode (generic binary)

Filename.class

Stage 1: Compilation

From slides of James Tam

A High Level View Of Translating/Executing Java Programs

Java interpreter (java)

Java bytecode (generic binary)

Filename.class

Machine language instruction (UNIX)

Machine language instruction (Windows)

Machine language instruction (Apple)

Stage 2: Interpreting and executing the byte code

From slides of James Tam

Java Instructions

• Each Java instruction must be followed by a semi-colon!

int num = 123;System.out.println(“Hello!");

Java OutputSystem.out.print(<string or variable name one> + <string or variable name two>..);

ORSystem.out.println(<string or variable name one> + <string or variable name two>..);

public class OutputExample1{ public static void main (String [] args) { int num = 123; // More on this shortly

System.out.println(“Hello!"); // prints to new line System.out.print(num); // prints to current line System.out.println("num="+num);}

}

Output : Some Escape Sequences For Formatting

Escape sequence Description

\t Horizontal tab

\r Carriage return

\n New line

\” Double quote

\\ Backslash

Variables• Variables must be declared before they can be

used.• Variable declaration:

– Creates a variable in memory.– Specify the name of the variable as well as the type

of information that it will store.– E.g. int num;

• Using variables– Only after a variable has been declared can it be

used.

Declaring Variables: Syntax

• Format:<type of information> <name of variable>;

• Example:char myFirstInitial;

• Variables can be initialized (set to a starting value) as they’re declared:char myFirstInitial = ‘j’;

int age = 30;

Some Built-In Types Of Variables In JavaType Description

byte 8 bit signed integer

short 16 bit signed integer

int 32 bit signed integer

long 64 bit signed integer

float 32 bit signed real number

double 64 bit signed real number

char 16 bit Unicode character (ASCII and beyond)

boolean 1 bit true or false value

String A sequence of characters between double quotes ("")

Location Of Variable Declarationspublic class <name of class>

{

public static void main (String[] args)

{

// Local variable declarations occur here

<< Program statements >>

: :

}

}

Java Constants

Reminder: constants are like variables in that they have a name and store a certain type of information but unlike variables they CANNOT change.

Format: final <constant type> <CONSTANT NAME> = <value>;

Example: final int SIZE = 100;

Location Of Constant Declarationspublic class <name of class>{ public static void main (String[] args) {

// Local constant declarations occur here (more later)// Local variable declarations

< Program statements >> : :

} }

Java 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 private protected public return short

static super switch synchronized this throw throws

transient try void volatile while

Common Java Operators / Operator Precedence

Precedence level

Operator Description Associativity

1 expression++

expression--

Post-increment

Post-decrement

Right to left

2 ++expression

--expression

+

-

!

~

(type)

Pre-increment

Pre-decrement

Unary plus

Unary minus

Logical negation

Bitwise complement

Cast

Right to left

Common Java Operators / Operator Precedence

Precedence level

Operator Description Associativity

3 *

/

%

Multiplication

Division

Remainder/modulus

Left to right

4 +

-

Addition or String concatenation

Subtraction

Left to right

5 <<

>>

Left bitwise shift

Right bitwise shift

Left to right

Common Java Operators / Operator Precedence

Precedence level

Operator Description Associativity

6 <

<=

>

>=

Less than

Less than, equal to

Greater than

Greater than, equal to

Left to right

7 = =

!=

Equal to

Not equal to

Left to right

8 & Bitwise AND Left to right

9 ^ Bitwise exclusive OR Left to right

Common Java Operators / Operator Precedence

Precedence level

Operator Description Associativity

10 | Bitwise OR Left to right

11 && Logical AND Left to right

12 || Logical OR Left to right

Common Java Operators / Operator Precedence

Precedence level

Operator Description Associativity

13 =

+=

-=

*=

/=

%=

&=

^=

|=

<<=

>>=

Assignment

Add, assignment

Subtract, assignment

Multiply, assignment

Division, assignment

Remainder, assignment

Bitwise AND, assignment

Bitwise XOR, assignment

Bitwise OR, assignment

Left shift, assignment

Right shift, assignment

Right to left

Post/Pre Operators

public class Order1{ public static void main (String [] args) { int num = 5; System.out.println(num); // 5 num++; System.out.println(num); // 6 ++num; System.out.println(num); //7 System.out.println(++num); //8 System.out.println(num++); //8 }}

Accessing Pre-Created Java Libraries

• It’s accomplished by placing an ‘import’ of the appropriate library at the top of your program.

• Syntax:import <Full library name>;

• Example:import java.util.Scanner;

Getting Text Input

• You can use the pre-written methods (functions) in the Scanner class.

• General structure:import java.util.Scanner;

main (String [] args){ Scanner <name of scanner> = new Scanner (System.in); <variable> = <name of scanner> .<method> (); }

Creating a scanner object (something that can scan user input)

Using the capability of the scanner object (actually getting user input)

Getting Text Input (2)import java.util.Scanner;

public class MyInput{ public static void main (String [] args) { String str1; int num1; Scanner in = new Scanner (System.in); System.out.print ("Type in an integer: "); num1 = in.nextInt (); System.out.print ("Type in a line: "); in.nextLine (); str1 = in.nextLine (); System.out.println ("num1:" +num1 +"\t str1:" + str1); }}

Useful Methods Of Class Scanner• nextInt ()• nextLong ()• nextFloat ()• nextDouble ()• nextLine () • next()

Decision Making In Java

• Java decision making constructs– if– if, else– if, else-if– switch

Decision Making: Logical Operators

Logical Operation Java

AND &&

OR ||

NOT !

Decision Making: If

Format:if (Boolean Expression) Body

Example:if (x != y) System.out.println("X and Y are not equal");

if ((x > 0) && (y > 0)) { System.out.println("X and Y are positive"); }

• Indenting the body of the branch is an important stylistic requirement of Java

• What distinguishes the body is either:

1.A semi colon (single statement branch)

2.Braces (a body that consists of multiple statements)

Decision Making: If, Else

Format:if (Boolean expression) Body of ifelse

Body of else

Example:if (x < 0) System.out.println("X is negative");else System.out.println("X is non-negative");

Example Program: If-Elseimport java.util.Scanner;

public class BranchingExample1{ public static void main (String [] args) { Scanner in = new Scanner(System.in); final int WINNING_NUMBER = 131313; int playerNumber = -1;

System.out.print("Enter ticket number: "); playerNumber = in.nextInt(); if (playerNumber == WINNING_NUMBER) System.out.println("You're a winner!"); else System.out.println("Try again."); }}

If, Else-If

Format:if (Boolean expression) Body of ifelse if (Boolean expression)

Body of first else-if : : :else if (Boolean expression)

Body of last else-ifelse Body of else

If, Else-If (2)

import java.util.Scanner;

public class BranchingExample2{ public static void main (String [] args) { Scanner in = new Scanner(System.in); int gpa = -1; System.out.print("Enter letter grade: "); gpa = in.nextInt();

If, Else-If (3) if (gpa == 4) System.out.println("A"); else if (gpa == 3) System.out.println("B"); else if (gpa == 2) System.out.println("C"); else if (gpa == 1) System.out.println("D"); else if (gpa == 0) System.out.println("F"); else System.out.println("Invalid letter grade"); }}

Alternative To Multiple Else-If’s: Switch

Format (character-based switch):switch (character variable name){

case '<character value>': Body break;

case '<character value>': Body break;

: default: Body

}

1 The type of variable in the brackets can be a byte, char, short, int or long

Alternative To Multiple Else-If’s: Switch (2)

Format (integer based switch):switch (integer variable name){

case <integer value>: Body break;

case <integer value>: Body break;

: default: Body

}

1 The type of variable in the brackets can be a byte, char, short, int or long

Looping Statements

Java Pre-test loops• For• While

Java Post-test loop• Do-while

While Loops

Format:while (Boolean expression) Body

Example:int i = 1;while (i <= 10){

// Some statements ; i = i + 1;

}

For Loops

Format:for (initialization; Boolean expression; update control)

Body

Example:for (i = 1; i <= 10; i++)

{

// some statements

i = i + 1;

}

Post-Test Loop: Do-While

• Recall: Post-test loops evaluate the Boolean expression after the body of the loop has executed.

• This means that post test loops will execute one or more times.

• Pre-test loops generally execute zero or more times.

Do-While LoopsFormat:

do

Body

while (Boolean expression);

Example: char ch = 'A';

do

{

System.out.println(ch);

ch++;

}

while (ch <= ‘D');

Output :ABCD

Arrays

• Arrays are a collection of elements of same typeint[] myInt = new int[3];myInt[0]=1;myInt[1]=2;myInt[2]=3;

Arrays (2)

Iterating an array :

int[] myInt = new int[10];for (int i=0; i<10; i++){ myInt[i]=i;

System.out.println(myInt[i]); }

Homeworks

• Dowload JDK and Eclipse• Read Chapter 2 + 3 from you course book..