Chapter 01 Java Programming Basic Java IDE JAVA INTELLIEJ

Chapter 1 Introduction to
Computers, Programs, and Java
1

Objectives
• To understand computer basics, programs, and operating systems (§§1.2–1.4).
• To describe the relationship between Java and the World Wide Web (§1.5).
• To understand the meaning of Java language specification, API, JDK, and IDE
(§1.6).
• To write a simple Java program (§1.7).
• To display output on the console (§1.7).
• To explain the basic syntax of a Java program (§1.7).
• To create, compile, and run Java programs (§1.8).
• To use sound Java programming style and document programs properly (§1.9).
• To explain the differences between syntax errors, runtime errors, and logic
errors (§1.10).
2

What is a Computer?
3
A computer consists of a CPU, memory, hard disk, floppy disk,
monitor, printer, and communication devices.
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

CPU
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
4
The central processing unit (CPU) is the brain of a computer. It
retrieves instructions from memory and executes them. The unit of
measurement of clock speed is the hertz (Hz), with 1 hertz equaling
1 pulse per second. In the 1990s, computers measured clock speed in
megahertz (MHz), but CPU speed has been improving continuously;
the clock speed of a computer is now usually stated in gigahertz
(GHz). Intel’s newest processors run at about 3 GHz.

Memory
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
5
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.

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. The
encoding scheme varies. For example,
character ‘J’ is represented by 01001010 in
one byte. A small number such as three can
be stored in a single byte. If computer needs
to store a large number that cannot fit into a
single byte, it uses a number of adjacent
bytes. No two data can share or split a same
byte. A byte is the minimum storage unit.
6
.
.
.
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

Storage Devices
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
7
Memory is volatile, 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 (hard
disks), CD drives (CD-R and CD-RW), and USB flash drives.

Output Devices: Monitor
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
8
The monitor displays information (text and graphics). The resolution
and dot pitch determine the quality of the display.

Monitor Resolution and Dot Pitch
9
The screen resolution specifies the number of pixels in
horizontal and vertical dimensions of the display device.
Pixels (short for “picture elements”) are tiny dots that form
an image on the screen. A common resolution for a 17-inch
screen, for example, is 1,024 pixels wide and 768 pixels
high. The resolution can be set manually. The higher the
resolution, the sharper and clearer the image is.
resolution
The dot pitch is the amount of space between pixels,
measured in millimeters. The smaller the dot pitch, the
sharper the display.
dot pitch

Communication Devices
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
10
A regular modem uses a phone line and can transfer data in a speed up to
56,000 bps (bits per second). A DSL (digital subscriber line) also uses a
phone line and can transfer data in a speed 20 times faster than a regular
modem. A cable modem uses the TV cable line maintained by the cable
company. A cable modem is as fast as a DSL. Network interface card
(NIC) is a device to connect a computer to a local area network (LAN).
The LAN is commonly used in business, universities, and government
organizations. A high-speed NIC, called 1000BaseT, can transfer data at
1000 mbps (million bits per second).

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.
11

Programming Languages
Machine Language Assembly Language High-Level Language
12
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:
1101101010011010

13
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

14
The high-level languages are English-like and easy to learn
and program. For example, the following is a high-level
language statement that computes the area of a circle with
radius 5:
area = 5 * 5 * 3.1415;

Popular High-Level Languages
15
Language Description
Ada
BASIC
C
C++
C#
COBOL
FORTRAN
Java
Pascal
Python
Visual
Basic
Named for Ada Lovelace, who worked on mechanical general-purpose computers. The Ada
language was developed for the Department of Defense and is used mainly in defense projects.
Beginner’s All-purpose Symbolic Instruction Code. It was designed to be learned and used easily
by beginners.
Developed at Bell Laboratories. C combines the power of an assembly language with the ease of
use and portability of a high-level language.
C++ is an object-oriented language, based on C.
Pronounced “C Sharp.” It is a hybrid of Java and C++ and was developed by Microsoft.
COmmon Business Oriented Language. Used for business applications.
FORmula TRANslation. Popular for scientific and mathematical applications.
Developed by Sun Microsystems, now part of Oracle. It is widely used for developing platform-
independent Internet applications.
Named for Blaise Pascal, who pioneered calculating machines in the seventeenth century. It is a
simple, structured, general-purpose language primarily for teaching programming.
A simple general-purpose scripting language good for writing short programs.
Visual Basic was developed by Microsoft and it enables the programmers to rapidly develop
graphical user interfaces.

Interpreting/Compiling Source Code
A program written in a high-level language is called a
source program or source code. Because a computer
cannot understand a source program, a source program
must be translated into machine code for execution. The
translation can be done using another programming tool
called an interpreter or a compiler.
16

Interpreting Source Code
An interpreter reads one statement from the source code,
translates it to the machine code or virtual machine code,
and then executes it right away, as shown in the following
figure. Note that a statement from the source code may be
translated into several machine instructions.
17

Compiling Source Code
A compiler translates the entire source code into a
machine-code file, and the machine-code file is then
executed, as shown in the following figure.
18

Operating Systems
The operating system (OS) is a
program that manages and
controls a computer’s activities.
The popular operating
systems for general-purpose
computers are Microsoft
Windows, Mac OS, and Linux.
Application programs, such as
a Web browser or a word
processor, cannot run unless
an operating system is
installed and running on the
computer.
19

Why Java?
20
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.

Java, Web, and Beyond
• Java can be used to develop standalone
applications.
• Java can be used to develop applications
running from a browser.
• Java can also be used to develop applications
for hand-held devices.
• Java can be used to develop applications for
Web servers.
21

Java’s History
The history of Java is very interesting. Java was originally designed for interactive television, but it
was too advanced technology for the digital cable television industry at the time. The history of Java
starts with the Green Team. Java team members (also known as Green Team), initiated this project to
develop a language for digital devices such as set-top boxes, televisions, etc. However, it was best
suited for internet programming. Later, Java technology was incorporated by Netscape.
The principles for creating Java programming were "Simple, Robust, Portable, Platform-
independent, Secured, High Performance, Multithreaded, Architecture Neutral, Object-Oriented,
Interpreted, and Dynamic". Java was developed by James Gosling, who is known as the father of
Java, in 1995. James Gosling and his team members started the project in the early '90s.
James Gosling - founder of java
22

Java’s History
Currently, Java is used in internet programming, mobile devices, games, e-business
solutions, etc. Following are given significant points that describe the history of Java.
1) James Gosling, Mike Sheridan, and Patrick Naughton initiated the Java language
project in June 1991. The small team of sun engineers called Green Team.
2) Initially it was designed for small, embedded systems in electronic appliances like set-
top boxes.
3) Firstly, it was called "Greentalk" by James Gosling, and the file extension was .gt.
4) After that, it was called Oak and was developed as a part of the Green project.
23

Java’s History
Why Java was named as "Oak"?
Java History from Oak to Java
5) Why Oak? Oak is a symbol of strength and chosen as a national tree of many countries like the U.S.A., France, Germany, Romania, etc.
6) In 1995, Oak was renamed as "Java" because it was already a trademark by Oak Technologies.
Why Java Programming named "Java"?
7) Why had they chose the name Java for Java language? The team gathered to choose a new name. The suggested words were "dynamic",
"revolutionary", "Silk", "jolt", "DNA", etc. They wanted something that reflected the essence of the technology: revolutionary, dynamic, lively, cool,
unique, and easy to spell, and fun to say.
According to James Gosling, "Java was one of the top choices along with Silk". Since Java was so unique, most of the team members preferred Java
than other names.
24

Java’s History
8) Java is an island in Indonesia where the first coffee was produced (called Java coffee). It is a kind of espresso bean. Java name
was chosen by James Gosling while having a cup of coffee nearby his office.
9) Notice that Java is just a name, not an acronym.
10) Initially developed by James Gosling at Sun Microsystems (which is now a subsidiary of Oracle Corporation) and released in
1995.
11) In 1995, Time magazine called Java one of the Ten Best Products of 1995.
12) JDK 1.0 was released on January 23, 1996. After the first release of Java, there have been many additional features added to
the language. Now Java is being used in Windows applications, Web applications, enterprise applications, mobile applications,
cards, etc. Each new version adds new features in Java.
25

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
26

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
27
Java is partially modeled on C++, but greatly
simplified and improved. Some people refer to
Java as "C++--" because it is like C++ but
with more functionality and fewer negative
aspects.

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
28
Java is inherently object-oriented.
Although many object-oriented languages
began strictly as procedural languages,
Java was designed from the start to be
object-oriented. Object-oriented
programming (OOP) is a popular
programming approach that is replacing
traditional procedural programming
techniques.
One of the central issues in software
development is how to reuse code. Object-
oriented programming provides great
flexibility, modularity, clarity, and
reusability through encapsulation,
inheritance, and polymorphism.

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
29
Distributed computing involves several
computers working together on a network.
Java is designed to make distributed
computing easy. Since networking
capability is inherently integrated into
Java, writing network programs is like
sending and receiving data to and from a
file.

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
30
You need an interpreter to run Java
programs. The programs are compiled into
the Java Virtual Machine code called
bytecode. The bytecode is machine-
independent and can run on any machine
that has a Java interpreter, which is part of
the Java Virtual Machine (JVM).

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
31
Java compilers can detect many problems
that would first show up at execution time
in other languages.
Java has eliminated certain types of error-
prone programming constructs found in
other languages.
Java has a runtime exception-handling
feature to provide programming support
for robustness.

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
32
Java implements several security
mechanisms to protect your system against
harm caused by stray programs.

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
33
Write once, run anywhere
With a Java Virtual Machine (JVM),
you can write one program that will
run on any platform.

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
34
Because Java is architecture neutral,
Java programs are portable. They can
be run on any platform without being
recompiled.

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
35
Java’s performance Because Java is
architecture neutral, Java programs are
portable. They can be run on any
platform without being recompiled.

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
36
Multithread programming is smoothly
integrated in Java, whereas in other
languages you have to call procedures
specific to the operating system to enable
multithreading.

• Java Is Simple
• Java Is Robust
• Java Is Secure
• Java Is Dynamic
37
Java was designed to adapt to an evolving
environment. New code can be loaded on the
fly without recompilation. There is no need for
developers to create, and for users to install,
major new software versions. New features can
be incorporated transparently as needed.

JDK Versions
38
Version Date
JDK Beta 1995
JDK 1.0 January 23, 1996[40]
JDK 1.1 February 19, 1997
J2SE 1.2 December 8, 1998
J2SE 1.3 May 8, 2000
J2SE 1.4 February 6, 2002
J2SE 5.0 September 30, 2004
Java SE 6 December 11, 2006
Java SE 7 July 28, 2011
Java SE 8 (LTS) March 18, 2014
Java SE 9 September 21, 2017
Java SE 10 March 20, 2018
Java SE 11 (LTS) September 25, 2018[41]
Java SE 15 September 15, 2020[42]
Java SE 17 (LTS) September 14, 2021
Java SE 21 (LTS) September 19, 2023 [43]

JDK Editions
• Java Standard Edition (J2SE)
• J2SE can be used to develop client-side standalone
applications or applets.
• Java Enterprise Edition (J2EE)
• J2EE can be used to develop server-side applications
such as Java servlets, Java ServerPages, and Java
ServerFaces.
• Java Micro Edition (J2ME).
• J2ME can be used to develop applications for mobile
devices such as cell phones.
This book uses J2SE to introduce Java
programming.
39

Popular Java IDEs
• NetBeans
• Eclipse
• JetBrains IDEA
40

A Simple Java Program
// This program prints Welcome to Java!
public class Welcome {
public static void main(String[] args) {
System.out.println("Welcome to Java!");
}
}
41
Listing 1.1
Welcome

Creating and Editing Using NotePad
To use NotePad, type
notepad Welcome.java
from the DOS prompt.
42

Creating and Editing Using WordPad
To use WordPad, type
write Welcome.java
from the DOS prompt.
43

Creating, Compiling, and Running
Programs
44

Compiling Java Source Code
You can port a source program to any machine with appropriate
compilers. The source program must be recompiled, however, because
the object program can only run on a specific machine. Nowadays
computers are networked to work together. Java was designed to run
object programs on any platform. With Java, you write the program
once, and compile the source program into a special type of object
code, known as bytecode. The bytecode can then run on any
computer with a Java Virtual Machine, as shown below. Java Virtual
Machine is a software that interprets Java bytecode.
45

Trace a Program Execution
46
}
}
Enter main method

47
}
}
Execute statement

48
}
}
print a message to the
console

Two More Simple Examples
49
WelcomeWithThreeMessages
ComputeExpression

Anatomy of a Java Program
• Class name
• Main method
• Statements
• Statement terminator
• Reserved words
• Comments
• Blocks
50

Class Name
Every Java program must have at least one class. Each class
has a name. By convention, class names start with an
uppercase letter. In this example, the class name is
Welcome.
51
}
}

Main Method
Line 2 defines the main method. In order to run a class, the
class must contain a method named main. The program is
executed from the main method.
52
}
}

Statement
A statement represents an action or a sequence of
actions. The statement System.out.println("Welcome to
Java!") in the program in Listing 1.1 is a statement to
display the greeting "Welcome to Java!“.
53
}
}

Statement Terminator
54
}
}
Every statement in Java ends with a semicolon (;).

Reserved words
Reserved words or keywords are words that have a
specific meaning to the compiler and cannot be used for
other purposes in the program. For example, when the
compiler sees the word class, it understands that the
word after class is the name for the class.
55
}
}

Blocks
56
A pair of braces in a program forms a block that groups
components of a program.
public class Test {
}
}
Class block
Method block

Special Symbols
57
Character Name Description
{}
()
[]
//
" "
;
Opening and closing
braces
Opening and closing
parentheses
Opening and closing
brackets
Double slashes
Opening and closing
quotation marks
Semicolon
Denotes a block to enclose statements.
Used with methods.
Denotes an array.
Precedes a comment line.
Enclosing a string (i.e., sequence of characters).
Marks the end of a statement.

{ … }
58
}
}

( … )
59
}
}

;
60
}
}

// …
61
}
}

" … "
62
}
}

Programming Style and
Documentation
•Appropriate Comments
•Naming Conventions
•Proper Indentation and Spacing Lines
•Block Styles
63

Appropriate Comments
Include a summary at the beginning of the program to
explain what the program does, its key features, its
supporting data structures, and any unique techniques it
uses.
Include your name, class section, instructor, date, and a
brief description at the beginning of the program.
64

Naming Conventions
• Choose meaningful and descriptive names.
• Class names:
• Capitalize the first letter of each word in the name. For
example, the class name ComputeExpression.
65

Proper Indentation and Spacing
• Indentation
• Indent two spaces.
• Spacing
• Use blank line to separate segments of the code.
66

Block Styles
Use end-of-line style for braces.
67
public class Test
{
public static void main(String[] args)
{
System.out.println("Block Styles");
}
}
public class Test {
System.out.println("Block Styles");
}
}
End-of-line
style
Next-line
style

Programming Errors
• Syntax Errors
• Detected by the compiler
• Runtime Errors
• Causes the program to abort
• Logic Errors
• Produces incorrect result
68

Syntax Errors
public class ShowSyntaxErrors {
public static main(String[] args) {
System.out.println("Welcome to Java);
}
}
69
ShowSyntaxErrors

Runtime Errors
public class ShowRuntimeErrors {
System.out.println(1 / 0);
}
}
70
ShowRuntimeErrors

Logic Errors
public class ShowLogicErrors {
System.out.println("Celsius 35 is Fahrenheit degree ");
System.out.println((9 / 5) * 35 + 32);
}
}
71
ShowLogicErrors

Chapter 01 Java Programming Basic Java IDE JAVA INTELLIEJ

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