Name of Course : Introduction to Java Programming

Lecturer: Alexander Shkolnik E- mail: shkol@bgu.ac.il Office Hours: Sun 12:00 - 14:00 build 37,room 520 Course number : 202.1.9031 Credits : 4 Course Site : http://www.cs.bgu.ac.il/~ipc202 1

Course Objectives

• The main purpose of the course - introduction to Java language

programming methods, based on new approaches in computer science.

• On the first part of the course students will acquire procedural programming:

software development technique that imposes a hierarchical structure on

the design of the programs. On the second part of the course students will

learn the principles of Object-Oriented Programming (OOP): programming

technique based on objects.

• Students will learn operation system Windows and Integrated Development

Environment (IDE) Eclipse, which provides first – class Java programming

tools.

• The course includes: algorithm building principles, basic Java commands,

control structure, arrays, different kinds of methods (including recursion

methods), principles of object-oriented programming (OOP), collections,

dynamic data structures and files manipulations.

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Course requirements : • 1. 13 x 3 hours lectures

• 2. 13 x 2 hours (4 x 2 lab, 9 x 2 frontal) practical lessons

• 3. 5 programming assignments (about 20 hours each)

(every assignment 6 % of the final grade).

The only 4 first assignments must be submitted frontally.

Submissions: alone only.

• 4. Final exam 3 hours long ( 70% of final grade,

a "Pass" requirement regarding final exam: 56 ) .

No auxiliary material allowed, except for a single two-sided

A4 paper sheet (neither printed nor copied).

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Our course site

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http://www.cs.bgu.ac.il/~ipc202/Main

Review computer basics

User

Application Programs

Operating System

Hardware

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HARDWARE VS SOFTWARE

● The hardware and software are the main components of the

computer system and therefore one is nothing without others.

● Computer hardware (חומרה) is the collection that constitutes

the physical components of the system.

● The software (תכנה) is the set of instructions that make the

hardware work.

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Computer Structure

CPU

Internal Memory

Input

Output

Mouse Keyboard Microphone Detectors

Monitor Speakers Motors External

Memory

Hard Disk CD / DVD Tape DiskOnKey

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CPU ( מעבד )

The Central Processing Unit (CPU) is the brain of a computer.

It retrieves instructions from memory and executes them. The CPU speed is

measured in megahertz (MHz), with 1 megahertz equaling 1 million pulses per second. The speed of the CPU has been improved continuously.

CPU

e.g., Disk, CD,

and Tape

Input

Devices

e.g., Keyboard,

Mouse

e.g., Monitor,

Printer

Communication

Devices

e.g., Modem,

and NIC

Storage

Devices

Memory Output

Devices

Bus

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Memory ( זיכרון ) Memory is to store data and program instructions for CPU to execute.

A memory unit is an ordered sequence of bytes, each holds eight bits. A

program and its data must be brought to memory before they can be

executed. A memory byte is never empty, but its initial content may be

meaningless to your program. The current content of a memory byte is lost

whenever new information is placed in it.

CPU

e.g., Disk, CD,

and Tape

Input

Devices

e.g., Keyboard,

Mouse

e.g., Monitor,

Printer

Communication

Devices

e.g., Modem,

and NIC

Storage

Devices

Memory Output

Devices

Bus

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Memory Unit : Byte

• Byte (בית) is a unit of digital information.

It is an ordered collection of 8 bits ( binary

digit), in which each bit denotes the binary

value of 1 or 0.

• number of bits (סיביות) used to encode a character of text in the computer, which depended on computer hardware architecture.

• A byte can represent 28 = 256 distinct values, such as the integers from 0 to 255.

• ASCII (American Standard Code for Information Interchange).

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How Data is Stored?

● Data of various kinds, such as numbers, characters, and strings, are encoded as a series of bits (zeros and ones).

● Computers use zeros and ones because digital devices have two stable states, which are referred to as zero and one by convention. The programmers need not to be concerned about the encoding and decoding of data, which is performed automatically by the system based on the encoding scheme.

● A byte is the minimum storage unit.

.

.

.

2000

2001

2002

2003

2004

.

.

.

01001010

01100001

01110110

01100001

00000011

Memory content

Memory address

Encoding for character ‘J’ Encoding for character ‘a’ Encoding for character ‘v’ Encoding for character ‘a’ Encoding for number 3

1 KB = 1,024 bytes

1 MB = 1,048,576 bytes

1 GB = 1,073,741,824 bytes

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● The modern computers are based on a stored-program concept introduced

by John Von Neumann.

In this stored-program concept, programs and data are stored in a separate

storage unit called memories and are treated the same.

Von Neumann architecture

Storage Devices ( התקני אחסון ) Memory is volatile ( נדיף ), because information is lost when the power is off.

Programs and data are permanently stored on storage devices and are

moved to memory when the computer actually uses them.

There are three main types of storage devices: Disk drives, CD drives and

Tape drives.

CPU

e.g., Disk, CD,

and Tape

Input

Devices

e.g., Keyboard,

Mouse

e.g., Monitor,

Printer

Communication

Devices

e.g., Modem,

and NIC

Storage

Devices

Memory Output

Devices

Bus

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USB flash drive

● A USB flash drive is a data storage device that includes flash

memory (a special type of memory that can be erased and

reprogrammed ) with an integrated Universal Serial Bus (USB)

interface.

● USB flash drives are typically removable and rewritable, and

physically much smaller than an CD.

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Operating system ( מערכת ההפעלה )

• An operating system ( OS ) is a software program that enables the

computer hardware to communicate and operate with the computer

software.

• An operating system also has a vital role to play in security. Its job

includes preventing unauthorized users from accessing the computer

system.

• Examples of popular modern operating systems include Microsoft

Windows, Android,, Linux, Mac OS X, and IBM z/OS.

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What's the difference between Mac/Apple, Windows and Linux ?

If operating systems “could talk”, this is what they would say:

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Operating system ( מערכת ההפעלה )

Do whatever you want, BUT stay within these boundaries,

and use what tools I give you.

Do only what I allow you to do, in the way that I make it

possible. Don't try to be smart. You aren't.

Do whatever you want with whatever you need to make it

work. You will have the minimal tools available, and you

have to look for it, otherwise, someone else will have the

appropriate tool for you. Use them.

Operating system, cont.

At the simplest level, an operating system does two things:

1. It manages the hardware and software resources of the computer

system. These resources include such things as the processor, memory,

disk space, etc.

2. It provides a stable, consistent way for applications to deal with the

hardware without having to know all the details of the hardware.

Today's major operating systems provide a

Graphical User Interface - GUI.

( ממשק משתמש להפעלת גרפיקה )

Elements of a GUI include such things as:

windows, pull-down menus, buttons, scroll

bars, iconic images. 17

Programs ● Computer programs, known as software, are

instructions to the computer.

You tell a computer what to do through programs.

Without programs, a computer is an empty machine.

Computers do not understand human languages, so

you need to use computer languages to communicate

with them.

● Programs are written using programming

languages ( שפות תכנות).

Lisp Pascal

VB

C Java C++

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Programming languages ● A programming language is a vocabulary and set of grammatical rules

for instructing a computer or computing device to perform specific tasks.

● The term programming language usually refers to high-level languages,

such as C, C++, COBOL, Java, FORTRAN, Ada, and Pascal.

● Each programming language has a unique set of keywords (words that it understands) and a special syntax for organizing program instructions. ● Each program defines its own grammatical rules that control which words

the computer understand.

History of software

● Alan Turing is credited with being the first person to come up with a theory

for software, which led to the two academic fields of computer science and

software engineering.

● The first generation of software for early stored program digital computers

in the late 1940s had its instructions written directly in binary code.

● Software would not be where it is today without Bill Gates

and Steve Jobs, two pioneers in the industry that had monumental impacts

on the history of software.

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● High-level programming languages, while simple compared to human

languages, are more complex than the languages the computer actually

understands, called machine languages (low level languages).

● Each different type of CPU has its own unique machine language.

● Lying between machine languages and high-level languages are languages

called assembly languages. Assembly languages are similar to machine

languages, but they are much easier to program.

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High level languages vs. machine languages

High level languages vs. machine languages

שפת מכונה

שפת סף

שפת עלית

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Programming Languages Machine Language Assembly Language High-Level Language

● Machine language is a set of primitive instructions built into every computer. The instructions are in the form of binary code, so you have to enter binary codes for various instructions.

Program with native machine language is a tedious process. Moreover the programs are highly difficult to read and modify.

For example: to add two numbers, you might write an

instruction in binary like this:

110110001101010011010

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Programming Languages Machine Language Assembly Language High-Level Language

● Assembly languages were developed to make programming easy. Since the computer cannot understand assembly language, however, a program called assembler is used to convert assembly language programs into machine code. For example:

to add two numbers, you might write an instruction in

assembly code like this:

ADDF3 R1, R2, R3

… ADDF3 R1, R2, R3

…

Assembly Source File

Assembler

… 1101101010011010

…

Machine Code File

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Programming Languages

Machine Language Assembly Language High-Level Language

● The high-level languages are English-like and easy

to learn and program.

For example 1: the following is a high-level language

statement that computes the area of a circle with

radius 5:

area = 5 * 5 * 3.1415;

For example 2: the following is a high-level language

statement that prints the string:

PRINT(“Welcome to Java course”);

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Programming Languages

6 best programming languages of 2018

Algorithm ( אלגוריתם )

An algorithm is a procedure or formula for

solving a problem.

The word derives from the name of the mathematician,

Mohammed ibn - Musa al - Khwarizmi, who was part of the

royal court in Baghdad and who lived from about 780 to 850.

Al-Khwarizmi's work is the likely source for the word algebra

as well.

Algorithms are implementation-

independent.

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How to make a computer do what you want, elegantly

and efficiently.

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Computer Science Algorithm

●To write a computer program, you

have to tell the computer, step by

step, exactly what you want it to

do.

● When you are telling the

computer what to do, you also get

to choose how it's going to do it.

That's where computer

algorithms come in.

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Basic computer operations

● Storage is a process through which digital data is

saved within a data storage device.

● Processing is the transformation of the input data to a

more meaningful form.

● Input/Output refers to the information that is passed into

or out of a computer.

Basic computer operators

• INPUT/OUTPUT ( פלט/אופרטורים קלט ) operators

• ASSIGNMENT ( אופרטורים השמה ) operators

• ARITHMETIC ( אופרטורים חשבון ) operators

• SELECTION ( אופרטורים בחירה ( operators

• PROGRAM CONTROL ( שינוי סדר הוראות ) operators

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Flowchart elements

What do the different flowchart shapes mean ?

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This shape tells you where the

flowchart begins and ends.

X = 15 In most flowcharts, the rectangle is the most common shape.

It is used to show a process, task, action, or operation.

A decision asks a question. The answer to the question

determines which arrow you follow out of the decision shape.

Lines with Arrows. You read a flowchart by following the lines

with arrows from shape to shape.

The lines with arrows determine the flow through the chart.

Grade A parallelogram represents input or output.

Flowchart examples

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THREE INTEGER’S MAX VALUE ( FLOWCHART )

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PSEUDO - CODE

• Pseudo-code is a tool that can be used to express algorithms more

precisely.

• Pseudo-code is a combination of programming code and ordinary English.

• Pseudo-code allows algorithms to be specified precisely without having to

worry about programming language syntax.

• There is currently no firmly established standard for Pseudo Code.

• Pseudo-code is not actually executed on a computer, it simply provides a

means for programmers to "Think out" their programs before they

implement them.

• A carefully prepared pseudo code program can be easily converted to a

programming language such as C++ or Java.

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HOW TO WRITE PSEUDO-CODE

• INPUT

– READ get input from a file

– GET get input from the keyboard

• ARITHMETIC / CALCULATIONS

– +_ * / ( ) =

• OUTPUT

– PRINT output to a printer

– WRITE output to a file

– DISPLAY output to a monitor

• STORE

– SET total_price to 0

– total_price = cost_price + tax

• COMPARE

– IF student is part time THEN add 1 to part time ELSE add 1 to full time ENDIF

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THREE INTEGER’S MAX VALUE ( PSEUDO - CODE )

C -ו , A Bשלושה מספרים למשתנים קלוט.1

MAXלמשתנה Aערך של השם. 2

MAX –ל Bערך של השם אז B > MAX אם. 3

MAX –ל Cערך של השם אז C > MAX אם. 4

MAXערכו של הדפס. 5

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THREE INTEGER’S MAX VALUE

( Java program )

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Software Development Process

• Understand Problem Definition

• Generalize & Decompose the problem

definition

• Develop Solution Algorithm

• Write the Java program Code

• Test and Debug the program

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Why Java?

The answer is that Java enables users to develop and

deploy applications on the Internet for servers, desktop

computers, and small hand-held devices.

The future of computing is being profoundly influenced

by the Internet, and Java promises to remain a big part

of that future. Java is the Internet programming

language.

Java is a general purpose programming language.

Java is the Internet programming language.

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Characteristics of Java • Java Is Simple

• Java Is Object-Oriented

• Java Is Distributed

• Java Is Interpreted

• Java Is Robust

• Java Is Secure

• Java Is Architecture-Neutral

• Java Is Portable

• Java's Performance

• Java Is Multithreaded

• Java Is Dynamic

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Important Java Concepts and Terminology

• JRE is the Java Runtime Environment and it creates a virtual machine within your

computer known as the JVM (Java Virtual Machine).

JRE is specific to your platform and is the environment in which Java byte code is

run.

• JDK (formerly SDK) is the Java Development Kit.

JDK = JRE + development tools.

▪ IDE is the Integrated Development Environment, have been created to support the

development of Java programs.

IDEs combine an editor, compiler and other Java support tools

into a single application (Eclipse in this course).

• To learn more about JDK, JRE, IDE etc., visit

http://java.sun.com/javase/technologies/index.jsp

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Running and Compiling Java

Java Code

Java Bytecode

JRE for Linux

JRE for Windows

Java compiler

Hello.java

javac Hello.java

Hello.class

Java interpreter translates bytecode to machine

code in JRE

JRE (Java Runtime Environment ) is the base set of

data files and programs (executables) which are

required to run Java Applications.

Java bytecode is the form of

instructions that the JVM executes

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● Java IDE ( for Integrated Development Environment )

is a software application which enables users to more easily write

and debug Java programs.

● Many IDEs provide features like syntax highlighting and code completion,

which help the user to code more easily.

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JAVA IDE

Eclipse • Eclipse is a multi-language software development

environment comprising an Integrated Development

Environment (IDE) .

• It is written mostly in Java.

• Before you can work with Eclipse, you'll need to download the

Java Development Kit (JDK).

• Eclipse is free software :

http://www.eclipse.org/downloads

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Programming Errors

● Even the most experienced programmers make mistakes, and knowing how to debug an application and find those mistakes is an important part of programming. ● Before you learn about the debugging process, however, it helps to know the types of bugs that you will need to find and fix.

Programming Errors • Syntax Errors ( ) דיקדוק שגיאות

Java, like all other programming languages, has its own syntax.

Syntax errors are a type of compiler error. This means they will be

detected immediately when the programmer tries to convert his source

code into a program.

For example: one rule of Java syntax is that all commands must end with

a semicolon (;).

• Runtime Errors ( ( ריצה זמן שגיאות

A runtime error means an error which happens, while the program is

running. Causes the program to abort.

• Logic Errors ( ( לוגיות שגיאות

These kinds of errors are a lot harder to fix, because you don't necessarily

know what causes the error. Produces incorrect result.

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● Debugging is the process of detecting and removing of existing and

potential errors (also called as ‘bugs’( in a software code that can cause it to behave unexpectedly or crash.

● Debugging tools (called debuggers) are used to identify coding errors at

various development stages.

● In the Eclipse the debugger provides many ways to see what your code is

doing while it runs.

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Programming Errors (Debugging)

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I wish you all the very best for your exams ( not only Java programming ), my students !