Introduction1

J.E.D.I
Introduction to
Programming I
Student's Manual
Version 1.3
June 2006
Introduction to Programming I 1
J.E.D.I
Author
Florence Tiu Balagtas
Team
Joyce Avestro
Florence Balagtas
Rommel Feria
Reginald Hutcherson
Rebecca Ong
John Paul Petines
Sang Shin
Raghavan Srinivas
Matthew Thompson
Requirements For the Laboratory Exercises
Supported Operating Systems
The NetBeans IDE 5.5 runs on operating systems that support the Java VM.
• Microsoft Windows XP Professional SP2 or newer
• Mac OS X 10.4.5 or newer
• Red Hat Fedora Core 3
• Solaris™ 10 Operating System Update 1 (SPARC® and x86/x64
Platform Edition)
NetBeans Enterprise Pack is also known to run on the following platforms:
• Microsoft Windows 2000 Professional SP4
• Solaris™ 8 OS (SPARC and x86/x64 Platform Edition) and Solaris 9 OS
(SPARC and x86/x64 Platform Edition)
• Various other Linux distributions
Minimum Hardware Configuration
Note: The NetBeans IDE's minimum screen resolution is 1024x768 pixels.
Operating System Processor Memory Disk Space
Microsoft Windows 500 MHz Intel Pentium III 512 MB 850 MB of free
disk space
Linux 500 MHz Intel Pentium III
workstation or equivalent
512 MB 450 MB of free
disk space
Solaris OS (SPARC) UltraSPARC II 450 MHz 512 MB 450 MB of free
disk space
Solaris OS (x86/x64
Platform Edition)
AMD Opteron 100 Series
1.8 GHz
512 MB 450 MB of free
disk space
Macintosh OS X
operating system
PowerPC G4 512 MB 450 MB of free
disk space
Recommended Hardware Configuration
Operating System Processor Memory Disk Speed
Microsoft Windows 1.4 GHz Intel Pentium III
workstation or equivalent
1 GB 1 GB of free disk
space
Linux 1.4 GHz Intel Pentium III
workstation or equivalent
1 GB 850 MB of free
disk space
Solaris OS (SPARC) UltraSPARC IIIi 1 GHz 1 GB 850 MB of free
disk space
Solaris OS (x86/x64
Platform Edition)
AMD Opteron 100 Series
1.8 GHz
1 GB 850 MB of free
disk space
Macintosh OS X
operating system
PowerPC G5 1 GB 850 MB of free
disk space
Required Software
NetBeans Enterprise Pack 5.5 Early Access runs on the Java 2 Platform
Standard Edition Development Kit 5.0 Update 1 or higher (JDK 5.0, version
1.5.0_01 or higher), which consists of the Java Runtime Environment plus
developer tools for compiling, debugging, and running applications written in
the Java language. Sun Java System Application Server Platform Edition 9 has
been tested with JDK 5.0 update 6.
• For Solaris, Windows, and Linux, you can download the JDK for your
platform from https://java.sun.com/j2se/1.5.0/download.html
• For Mac OS X, Java 2 Platform Standard Edition (J2SE) 5.0 Release 4, is
required. You can download the JDK from Apple's Developer Connection
site. Start here: https://developer.apple.com/java (you must register to
download the JDK).
For more information, please visit:
https://www.netbeans.org/community/releases/40/relnotes.html
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Table of Contents
1 Introduction to Computer Programming..............................................................10
1.1 Objectives............................................................................................... 10
1.2 Introduction............................................................................................. 10
1.3 Basic Components of a Computer................................................................11
1.3.1 Hardware.......................................................................................... 11
1.3.1.1 The Central Processing Unit.......................................................... 11
1.3.1.2 Memory .................................................................................... 11
1.3.1.3 Input and Output Devices............................................................. 12
1.3.2 Software........................................................................................... 12
1.4 Overview of Computer Programming Languages........................................... 13
1.4.1 What is a Programming Language?....................................................... 13
1.4.2 Categories of Programming Languages..................................................13
1.5 The Program Development Life Cycle...........................................................14
1.5.1 Problem Definition............................................................................. 15
1.5.2 Problem Analysis............................................................................... 15
1.5.3 Algorithm design and representation.................................................... 16
1.5.3.1 Flowcharting Symbols and their meanings...................................... 17
1.5.4 Coding and Debugging....................................................................... 18
1.6 Number Systems and Conversions.............................................................. 19
1.6.1 Decimal............................................................................................ 19
1.6.2 Binary.............................................................................................. 19
1.6.3 Octal................................................................................................ 19
1.6.4 Hexadecimal..................................................................................... 19
1.6.5 Conversions...................................................................................... 20
1.6.5.1 Decimal to Binary / Binary to Decimal............................................ 20
1.6.5.2 Decimal to Octal (or Hexadecimal)/Octal (or Hexadecimal) to Decimal....
21
1.6.5.3 Binary to Octal / Octal to Binary.................................................... 22
1.6.5.4 Binary to Hexadecimal / Hexadecimal to Binary............................... 23
1.7 Exercises................................................................................................. 24
1.7.1 Writing Algorithms............................................................................. 24
1.7.2 Number Conversions.......................................................................... 24
2 Introduction to Java........................................................................................ 25
2.1 Objectives............................................................................................... 25
2.2 Java Background...................................................................................... 25
2.2.1 A little Bit of History .......................................................................... 25
2.2.2 What is Java Technology?................................................................... 25
2.2.2.1 A programming language............................................................. 25
2.2.2.2 A development environment......................................................... 25
2.2.2.3 An application environment.......................................................... 25
2.2.2.4 A deployment environment........................................................... 26
2.2.3 Some Features of Java........................................................................ 26
2.2.3.1 The Java Virtual Machine.............................................................. 26
2.2.3.2 Garbage Collection...................................................................... 26
2.2.3.3 Code Security............................................................................. 27
2.2.4 Phases of a Java Program....................................................................28
3 Getting to know your Programming Environment................................................. 29
3.1 Objectives............................................................................................... 29
3.2 Introduction............................................................................................. 29
3.3 My First Java Program............................................................................... 29
3.4 Using a Text Editor and Console................................................................. 30
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3.4.1 Errors .............................................................................................. 40
3.4.1.1 Syntax Errors............................................................................. 40
3.4.1.2 Run-time Errors.......................................................................... 41
3.5 Using NetBeans........................................................................................ 42
3.6 Exercises................................................................................................. 55
3.6.1 Hello World!...................................................................................... 55
3.6.2 The Tree........................................................................................... 55
4 Programming Fundamentals............................................................................. 56
4.1 Objectives............................................................................................... 56
4.2 Dissecting my first Java program................................................................ 56
4.3 Java Comments........................................................................................ 58
4.3.1 C++-Style Comments.........................................................................58
4.3.2 C-Style Comments............................................................................. 58
4.3.3 Special Javadoc Comments................................................................. 58
4.4 Java Statements and blocks....................................................................... 59
4.5 Java Identifiers........................................................................................ 60
4.6 Java Keywords......................................................................................... 61
4.7 Java Literals............................................................................................ 62
4.7.1 Integer Literals ................................................................................. 62
4.7.2 Floating-Point Literals ........................................................................ 62
4.7.3 Boolean Literals ................................................................................ 62
4.7.4 Character Literals .............................................................................. 63
4.7.5 String Literals ................................................................................... 63
4.8 Primitive data types.................................................................................. 64
4.8.1 Logical - boolean............................................................................... 64
4.8.2 Textual – char................................................................................... 64
4.8.3 Integral – byte, short, int & long.......................................................... 65
4.8.4 Floating Point – float and double.......................................................... 66
4.9 Variables................................................................................................. 67
4.9.1 Declaring and Initializing Variables....................................................... 67
4.9.2 Outputting Variable Data.................................................................... 68
4.9.3 System.out.println() vs. System.out.print() ......................................... 68
4.9.4 Reference Variables vs. Primitive Variables............................................ 69
4.10 Operators.............................................................................................. 70
4.10.1 Arithmetic operators......................................................................... 70
4.10.2 Increment and Decrement operators................................................... 73
4.10.3 Relational operators......................................................................... 75
4.10.4 Logical operators.............................................................................. 78
4.10.4.1 && (logical AND) and & (boolean logical AND)............................... 79
4.10.4.2 || (logical OR) and | (boolean logical inclusive OR).........................81
4.10.4.3 ^ (boolean logical exclusive OR).................................................. 83
4.10.4.4 ! (logical NOT).......................................................................... 84
4.10.5 Conditional Operator (?:).................................................................. 85
4.10.6 Operator Precedence........................................................................ 87
4.11 Exercises............................................................................................... 88
4.11.1 Declaring and printing variables......................................................... 88
4.11.2 Getting the average of three numbers................................................. 88
4.11.3 Output greatest value....................................................................... 88
4.11.4 Operator precedence........................................................................ 88
5 Getting Input from the Keyboard....................................................................... 89
5.1 Objectives............................................................................................... 89
5.2 Using BufferedReader to get input.............................................................. 89
5.3 Using JOptionPane to get input................................................................... 93
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5.4 Exercises................................................................................................. 95
5.4.1 Last 3 words (BufferedReader version).................................................. 95
5.4.2 Last 3 words (JOptionPane version)...................................................... 95
6 Control Structures........................................................................................... 96
6.1 Objectives............................................................................................... 96
6.2 Decision Control Structures........................................................................ 96
6.2.1 if statement...................................................................................... 96
6.2.2 if-else statement............................................................................... 98
6.2.3 if-else-if statement........................................................................... 100
6.2.4 Common Errors when using the if-else statements:...............................101
6.2.5 Example for if-else-else if.................................................................. 102
6.2.6 switch statement............................................................................. 103
6.2.7 Example for switch........................................................................... 105
6.3 Repetition Control Structures....................................................................106
6.3.1 while loop....................................................................................... 106
6.3.2 do-while loop................................................................................... 108
6.3.3 for loop........................................................................................... 109
6.4 Branching Statements............................................................................. 110
6.4.1 break statement.............................................................................. 110
6.4.1.1 Unlabeled break statement......................................................... 110
6.4.1.2 Labeled break statement............................................................ 111
6.4.2 continue statement.......................................................................... 112
6.4.2.1 Unlabeled continue statement..................................................... 112
6.4.2.2 Labeled continue statement........................................................ 112
6.4.3 return statement.............................................................................. 113
6.5 Exercises............................................................................................... 114
6.5.1 Grades........................................................................................... 114
6.5.2 Number in words.............................................................................. 114
6.5.3 Hundred Times................................................................................ 114
6.5.4 Powers........................................................................................... 114
7 Java Arrays.................................................................................................. 115
7.1 Objectives............................................................................................. 115
7.2 Introduction to arrays.............................................................................. 115
7.3 Declaring Arrays..................................................................................... 116
7.4 Accessing an array element...................................................................... 118
7.5 Array length........................................................................................... 119
7.6 Multidimensional Arrays........................................................................... 120
7.7 Exercises............................................................................................... 121
7.7.1 Days of the Week............................................................................. 121
7.7.2 Greatest number.............................................................................. 121
7.7.3 Addressbook Entries......................................................................... 121
8 Command-line Arguments.............................................................................. 122
8.1 Objectives............................................................................................. 122
8.2 Command-line arguments........................................................................ 122
8.3 Command-line arguments in NetBeans...................................................... 124
8.4 Exercises............................................................................................... 128
8.4.1 Print arguments............................................................................... 128
8.4.2 Arithmetic Operations....................................................................... 128
9 Working with the Java Class Library................................................................. 129
9.1 Objectives............................................................................................. 129
9.2 Introduction to Object-Oriented Programming.............................................129
9.3 Classes and Objects................................................................................ 130
9.3.1 Difference Between Classes and Objects.............................................. 130
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9.3.2 Encapsulation.................................................................................. 131
9.3.3 Class Variables and Methods.............................................................. 131
9.3.4 Class Instantiation........................................................................... 132
9.4 Methods................................................................................................ 133
9.4.1 What are Methods and Why Use Methods?........................................... 133
9.4.2 Calling Instance Methods and Passing Variables....................................134
9.4.3 Passing Variables in Methods............................................................. 135
9.4.3.1 Pass-by-value........................................................................... 135
9.4.3.2 Pass-by-reference...................................................................... 136
9.4.4 Calling Static Methods...................................................................... 137
9.4.5 Scope of a variable........................................................................... 138
9.5 Casting, Converting and Comparing Objects............................................... 141
9.5.1 Casting Primitive Types..................................................................... 141
9.5.2 Casting Objects............................................................................... 143
9.5.3 Converting Primitive Types to Objects and Vice Versa............................145
9.5.4 Comparing Objects........................................................................... 146
9.5.5 Determining the Class of an Object..................................................... 148
9.6 Exercises............................................................................................... 149
9.6.1 Defining terms................................................................................. 149
9.6.2 Java Scavenger Hunt........................................................................ 149
10 Creating your own Classes............................................................................ 150
10.1 Objectives............................................................................................ 150
10.2 Defining your own classes...................................................................... 151
10.3 Declaring Attributes.............................................................................. 152
10.3.1 Instance Variables.......................................................................... 152
10.3.2 Class Variables or Static Variables.................................................... 153
10.4 Declaring Methods................................................................................ 153
10.4.1 Accessor methods........................................................................... 154
10.4.2 Mutator Methods............................................................................ 155
10.4.3 Multiple Return statements.............................................................. 156
10.4.4 Static methods............................................................................... 156
10.4.5 Sample Source Code for StudentRecord class..................................... 157
10.5 The this reference................................................................................. 159
10.6 Overloading Methods............................................................................. 160
10.7 Declaring Constructors........................................................................... 162
10.7.1 Default Constructor........................................................................ 162
10.7.2 Overloading Constructors................................................................ 162
10.7.3 Using Constructors......................................................................... 163
10.7.4 The this() Constructor Call............................................................... 164
10.8 Packages............................................................................................. 165
10.8.1 Importing Packages........................................................................ 165
10.8.2 Creating your own packages............................................................ 165
10.8.3 Setting the CLASSPATH.................................................................. 166
10.9 Access Modifiers................................................................................... 168
10.9.1 default access (also called package accessibility)................................ 168
10.9.2 public access................................................................................. 168
10.9.3 protected access............................................................................ 169
10.9.4 private access................................................................................ 169
10.10 Exercises........................................................................................... 170
10.10.1 Address Book Entry....................................................................... 170
10.10.2 AddressBook................................................................................ 170
11 Inheritance, Polymorphism and Interfaces....................................................... 171
11.1 Objectives............................................................................................ 171
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11.2 Inheritance.......................................................................................... 171
11.2.1 Defining Superclasses and Subclasses............................................... 172
11.2.2 The super keyword......................................................................... 174
11.2.3 Overriding Methods........................................................................ 175
11.2.4 Final Methods and Final Classes........................................................176
11.3 Polymorphism...................................................................................... 177
11.4 Abstract Classes................................................................................... 179
11.5 Interfaces............................................................................................ 181
11.5.1 Why do we use Interfaces?.............................................................. 181
11.5.2 Interface vs. Abstract Class..............................................................181
11.5.3 Interface vs. Class.......................................................................... 182
11.5.4 Creating Interfaces......................................................................... 182
11.5.5 Relationship of an Interface to a Class............................................... 184
11.5.6 Inheritance among Interfaces...........................................................184
11.6 Exercises............................................................................................. 185
11.6.1 Extending StudentRecord................................................................ 185
11.6.2 The Shape abstract class................................................................. 185
12 Basic Exception Handling.............................................................................. 186
12.1 Objectives............................................................................................ 186
12.2 What are Exceptions?............................................................................ 186
12.3 Handling Exceptions.............................................................................. 186
12.4 Exercises............................................................................................. 189
12.4.1 Catching Exceptions1...................................................................... 189
12.4.2 Catching Exceptions 2..................................................................... 189
Appendix A : Java and NetBeans Installation.........................................................190
Installing Java in Ubuntu Dapper..................................................................... 191
Installing Java in Windows............................................................................. 196
Installing NetBeans in Ubuntu Dapper.............................................................. 200
Installing NetBeans in Windows....................................................................... 208
Appendix B: Getting to know your Programming Environment (Windows XP version).. 215
My First Java Program................................................................................... 215
Using a Text Editor and Console...................................................................... 216
Setting the Path........................................................................................ 229
Using NetBeans............................................................................................ 230
Appendix D : Machine Problems.......................................................................... 240
Machine Problem 1: Phone Book...................................................................... 240
Machine Problem 2: Minesweeper.................................................................... 241
Machine Problem 3: Number Conversion...........................................................242
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Revision History
For Version 1.3
June 2006
Section Details
Appendix A and B, Chapter 3:Getting
to know your programming
environment
Switch to Netbeans 5.5 Beta Version
Appendix A, Chapter 3:Getting to
know your programming environment
Switch from Redhat Linux to Ubuntu Dapper
Appendix F: Additional Exercises Added (Teacher's manual)-c/o JEDI member
school teachers
For Version 1.2
January 2006
Section Details
Version Number Change from 1.1 to 1.2
Chapter 3: Gettting to know your
programming environment
Appendix A
Change Netbeans/netbeans to NetBeans
Chapter 4: Programming
Fundamentals
List of Java keywords
Chapter 10: Creating your own classes Coding guidelines: filenames should have the
same name as the public class name
Master Documents Added to list of references
For Version 1.1
August 2005
Section Details
Version Number Change from 1.0 to 1.1
Revision History Added
Appendix E: Hands-on Lab Exercises Added (c/o Sang)
Chapter 10: Creating Your own classes Added subsection on How to set classpath at
packages section
Chapter 11: Inheritance, Interfaces
and Polymorphism
Polymorphism section
• Added example that uses another class
whose method can receive a reference
variable
Interface
• Added sections
• Why do we use Interfaces?
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Section Details
• Interface vs. Abstract Class
• Interface vs. Class
• Relationship of an Interface to a Class
• Inheritance among Interfaces
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1 Introduction to Computer
Programming
1.1 Objectives
In this section, we will be discussing the basic components of a computer, both hardware
and software. We will also be giving a brief overview of programming languages and the
program development life cycle. Finally, different number systems and conversions from
one type to another will be discussed.
At the end of the lesson, the student should be able to:
• Identify the different components of a computer
• Know about programming languages and their categories
• Understand the program development life cycle and apply it in problem solving
• Learn the different number systems and their conversions
1.2 Introduction
A computer is a machine that performs a variety of tasks according to specific
instructions. It is a data processing machine which accepts data via an input device and
its processor manipulates the data according to a program.
The computer has two major components. The first one is the Hardware which is the
tangible part of the computer. It is composed of electronic and mechanical parts.
The second major component is the software which is the intangible part of a computer.
It consists of data and the computer programs.
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1.3 Basic Components of a Computer
1.3.1 Hardware
1.3.1.1 The Central Processing Unit
The processor is the “brain” of the computer. It contains millions of extremely tiny
electrical parts. It does the fundamental computing within the system. Examples of
processors are Pentium, Athlon and SPARC.
1.3.1.2 Memory
The memory is where data and instructions needed by the CPU to do its appointed tasks
can be found. It is divided into several storage locations which have corresponding
addresses. The CPU accesses the memory with the use of these addresses.
1. Main Memory
The main memory is very closely connected to the processor. It is used to hold programs
and data, that the processor is actively working with. It is not used for long-term
storage. It is sometimes called the RAM (Random Access Memory).
The computer's main memory is considered as volatile storage. This means that once
the computer is turned off, all information residing in the main memory is erased.
2. The Secondary Memory
The secondary memory is connected to main memory. It is used to hold programs and
data for long term use. Examples of secondary memory are hard disks and cd-rom.
Secondary memory is considered as non-volatile storage. This means that information
residing in secondary memory is not erased after the computer is turned off.
Main
Memory
Secondary
Memory Property
Fast Slow Speed
Expensive Cheap Price
Low High Capacity
Yes No Volatile
Table 1: Comparison between main memory and secondary memory
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1.3.1.3 Input and Output Devices
Input and output devices allows a computer system to interact with the outside world by
moving data into and out of the system.
Examples of input devices are keyboards, mice and microphones. Examples of output
devices are monitors, printers and speakers.
1.3.2 Software
A software is the program that a computer uses in order to function. It is kept on some
hardware device like a hard disk, but it itself is intangible. The data that the computer
uses can be anything that a program needs. Programs acts like instructions for the
processor.
Some Types of Computer Programs:
1. Systems Programs
• Programs that are needed to keep all the hardware and software systems running
together smoothly
• Examples:
• Operating Systems like Linux, Windows, Unix, Solaris, MacOS
2. Application Programs
• Programs that people use to get their work done
• Examples:
• Word Processor
• Game programs
• Spreadsheets
3. Compilers
• The computer understands only one language: machine language. Machine
language is in the form of ones and zeros. Since it is highly impractical for people
to create programs out of zeros and ones, there must be a way of translating or
converting a language which we understand into machine language, for this
purpose, there exists compilers.
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1.4 Overview of Computer Programming
Languages
1.4.1 What is a Programming Language?
A programming language is a standardized communication technique for expressing
instructions to a computer. Like human languages, each language has its own syntax
and grammar.
Programming languages enable a programmer to precisely specify what data a computer
will act upon, how these data will be stored/transmitted, and precisely what actions to
take under various circumstances.
There are different types of programming languages that can be used to create
programs, but regardless of what language you use, these instructions are translated
into machine language that can be understood by computers.
1.4.2 Categories of Programming Languages
1. High-level Programming Languages
• A high-level programming language is a programming language that is more userfriendly,
to some extent platform-independent, and abstract from low-level
computer processor operations such as memory accesses. A programming
statement may be translated into one or several machine instructions by a
compiler.
• Examples are Java, C, C++, Basic, Fortran
2. Low-level Assembly Language
• Assembly languages are similar to machine languages, but they are much easier to
program in because they allow a programmer to substitute names for numbers.
Assembly languages are available for each CPU family, and each assembly
instruction is translated into one machine instruction by an assembler program.
Note: The terms "high-level" and "low-level" are inherently relative. Originally, assembly
language was considered low-level and COBOL, C, etc. were considered high-level. Many
programmers today might refer to these latter languages as low-level.
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1.5 The Program Development Life Cycle
Programmers do not sit down and start writing code right away when trying to make a
computer program. Instead, they follow an organized plan or methodology, that breaks
the process into a series of tasks.
Here are the basic steps in trying to solve a problem on the computer:
1. Problem Definition
2. Problem Analysis
3. Algorithm design and representation (Pseudocode or flowchart)
4. Coding and debugging
In order to understand the basic steps in solving a problem on a computer, let us define
a single problem that we will solve step-by-step as we discuss the problem solving
methodologies in detail. The problem we will solve will be defined in the next section.
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1.5.1 Problem Definition
A programmer is usually given a task in the form of a problem. Before a program can be
designed to solve a particular problem, the problem must be well and clearly defined first
in terms of its input and output requirements.
A clearly defined problem is already half the solution. Computer programming requires
us to define the problem first before we even try to create a solution.
Let us now define our example problem:
“Create a program that will determine the number of times a name occurs in a list.”
1.5.2 Problem Analysis
After the problem has been adequately defined, the simplest and yet the most efficient
and effective approach to solve the problem must be formulated.
Usually, this step involves breaking up the problem into smaller and simpler subproblems.
Example Problem:
Determine the number of times a name occurs in a list
Input to the program:
list of names, name to look for
Output of the program:
the number of times the name occurs in a list
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1.5.3 Algorithm design and representation
Once our problem is clearly defined, we can now set to finding a solution. In computer
programming, it is normally required to express our solution in a step-by-step manner.
An Algorithm is a clear and unambiguous specification of the steps needed to solve a
problem. It may be expressed in either Human language (English, Tagalog), through a
graphical representation like a flowchart or through a pseudocode, which is a cross
between human language and a programming language.
Now given the problem defined in the previous sections, how do we express our general
solution in such a way that it is simple yet understandable?
Expressing our solution through Human language:
1. Get the list of names
2. Get the name to look for, let's call this the keyname
3. Compare the keyname to each of the names in the list
4. If the keyname is the same with a name in the list, add 1 to the count
5. If all the names have been compared, output the result
Expressing our solution through a flowchart:
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YES
Figure 1.1: Example of a flow chart
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Expressing our solution through pseudocode:
Let nameList = List of Names
Let keyName = the name to be sought
Let Count = 0
For each name in NameList do the following
if name == keyName
Count = Count + 1
Display Count
Figure 1.2: Example of a pseudocode
1.5.3.1 Flowcharting Symbols and their meanings
A flowchart is a design tool used to graphically represent the logic in a solution.
Flowcharts typically do not display programming language commands. Rather, they state
the concept in English or mathematical notation.
Here are some guidelines for commonly used symbols in creating flowcharts. You can use
any symbols in creating your flowcharts, as long as you are consistent in using them.
Symbol Name Meaning
Process Symbol
Represents the process of executing a defined
operation or groups of operations that results in a
change in value, form, or location of information.
Also functions as the default symbol when no
other symbol is available.
Input/Output
(I/O) Symbol
Represents an I/O function, which makes data
available for processing (input) or displaying
(output)of processed information.
Flowline Symbol
Represents the sequence of available information
and executable operations.The lines connect
other symbols, and the arrowheads are
mandatory only for right-to-left and bottom-totop
flow.
Annotation
Symbol
Represents the addition of descriptive
information, comments, or explanatory notes as
clarification. The vertical line and the broken line
may be placed on the left, as shown, or on the
right.
Decision Symbol
Represents a decision that determines which of a
number of alternative paths is to be followed.
Terminal Symbol
Represents the beginning, the end, or a point of
interruption or delay in a program.
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Symbol Name Meaning
Connector
Symbol
Represents any entry from, or exit to, another
part of the flowchart. Also serves as an off-page
connector.
Predefined
Process Symbol
Represents a named process consisting of one or
more operations or program steps that are
specified elsewhere.
Table 2: Flowchart Symbols
1.5.4 Coding and Debugging
After constructing the algorithm, it is now possible to create the source code. Using the
algorithm as basis, the source code can now be written using the chosen programming
language.
Most of the time, after the programmer has written the program, the program isn't 100%
working right away. The programmer has to add some fixes to the program in case of
errors (also called bugs) that occurs in the program. This process of is called
debugging.
There are two types of errors that a programmer will encounter along the way. The first
one is compile-time error, and the other is runtime error.
Compile-Time Errors occur if there is a syntax error in the code. The compiler will
detect the error and the program won't even compile. At this point, the programmer is
unable to form an executable that a user can run until the error is fixed.
Forgetting a semi-colon at the end of a statement or misspelling a certain command, for
example, is a compile-time error. It's something the compiler can detect as an error.
Compilers aren't perfect and so can't catch all errors at compile time. This is especially
true for logic errors such as infinite loops. This type of error is called runtime error.
For example, the actual syntax of the code looks okay. But when you follow the code's
logic, the same piece of code keeps executing over and over again infinitely so that it
loops. In such a case, compilers aren't really smart enough to catch all of these types of
errors at compile-time, and therefore, the program compiles fine into an executable file.
However, and unfortunately, when the end-user runs the program, the program (or even
their whole computer) freezes up due to an infinite loop. Other types of run-time errors
are when an incorrect value is computed, the wrong thing happens, etc.
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1.6 Number Systems and Conversions
Numbers can be represented in a variety of ways. The representation depends on what is
called the BASE. The following are the four most common representations.
1.6.1 Decimal
We normally represent numbers in their decimal form. Numbers in decimal form are in
base 10. This means that the only digits that appear are 0-9. Here are examples of
numbers written in decimal form:
12610 (normally written as just 126)
1110 (normally written as just 11)
1.6.2 Binary
Numbers in binary form are in base 2. This means that the only legal digits are 0 and 1.
We need to write the subscript 2 to indicate that the number is a binary number. Here
are examples of numbers written in binary form:
11111102
10112
1.6.3 Octal
Numbers in octal form are in base 8. This means that the only legal digits are 0-7. We
need to write the subscript 8 to indicate that the number is an octal number. Here are
examples of numbers written in octal form:
1768
138
1.6.4 Hexadecimal
Numbers in hexadecimal form are in base 16. This means that the only legal digits are 0-
9 and the letters A-F (or a-f, lowercase or uppercase does not matter). We need to write
the subscript 16 to indicate that the number is a hexadecimal number. Here are
examples of numbers written in hexadecimal form:
7E16
B16
Hexadecimal 0 1 2 3 4 5 6 7 8 9 A B C D E F
Decimal Equivalent
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
15
Table 3: Hexadecimal Numbers and their Equivalence to decimal numbers
Decimal Binary Octal Hexadecimal
12610 11111102 1768 7E16
1110 10112 138 B16
Table 4: Summary of Examples
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1.6.5 Conversions
1.6.5.1 Decimal to Binary / Binary to Decimal
To convert a decimal number to binary, continuously divide the number by 2 and get the
remainder (which is either 0 or 1), and get that number as a digit of the binary form of
the number. Get the quotient and divide that number again by 2 and repeat the whole
process until the quotient reaches 0 or 1. We then get all the remainders starting from
the last remainder, and the result is the binary form of the number.
NOTE: For the last digit which is already less than the divisor (which is 2) just copy the
value to the remainder portion.
For Example:
12610 = ? 2
Quotient Remainder
126 / 2 = 63 0
63 / 2 = 31 1
31 / 2 = 15 1
15 / 2 = 7 1
7 / 2 = 3 1
3 / 2 = 1 1
1 / 2 = 1
Write it this way
So, writing the remainders from the bottom up, we get the binary number 11111102
To convert a binary number to decimal, we multiply the binary digit to "2 raised to the
position of the binary number". We then add all the products to get the resulting decimal
number.
For Example:
11111102 = ? 10
Position 6 5 4 3 2 1 0
Binary
Digits 1 1 1 1 1 1 0
0 x 20 = 0
1 x 21 = 2
1 x 22 = 4
1 x 23= 8
1 x 24= 16
1 x 25 = 32
1 x 26 = 64
TOTAL: 126
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1.6.5.2 Decimal to Octal (or Hexadecimal)/Octal (or Hexadecimal) to Decimal
Converting decimal numbers to Octal or hexadecimal is basically the same as converting
decimal to binary. However, instead of having 2 as the divisor, you replace it with 8(for
octal) or 16 (for hexadecimal).
For Example (Octal):
12610 = ? 8
Quotient Remainder
126 / 8 = 15 6
15 / 8 = 1 7
1 / 8 = 1
Write it this way
So, writing the remainders from the bottom up, we get the octal number 1768
For Example (Hexadecimal):
12610 = ? 16
Quotient Remainder
126 / 16 = 7
14 (equal to hex
digit E)
7 / 16 = 7
Write it this way
So, writing the remainders from the bottom up, we get the hexadecimal number 7E16
* * *
Converting octal or hexadecimal numbers is also the same as converting binary numbers
to decimal. To do that, we will just replace the base number 2 with 8 for Octal and 16 for
hexadecimal.
For Example (Octal):
1768 = ? 10
Position 2 1 0
Octal Digits 1 7 6
6 x 80 = 6
7 x 81 = 56
1 x 82 = 64
TOTAL: 126
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For Example (Hexadecimal):
7E16 = ? 10
Position 1 0
Hex Digits 7 E
14 x 160 = 14
7 x 161 = 112
TOTAL: 126
1.6.5.3 Binary to Octal / Octal to Binary
To convert from binary numbers to octal, we partition the binary number into groups of 3
digits (from right to left), and pad it with zeros if the number of digits is not divisible by
3. We then convert each partition into its corresponding octal digit. The following is a
table showing the binary representation of each octal digit.
Octal Digit Binary
Representation
0 000
1 001
2 010
3 011
4 100
5 101
6 110
7 111
Table 5: Octal Digits and their corresponding binary represenation
For Example:
11111102 = ? 8
0 0 1 1 1 1 1 1 0
1 7 6
Equivalent octal number
Converting octal numbers to binary is just the opposite of what is given above. Simply
convert each octal digit into its binary representation (given the table) and concatenate
them. The result is the binary representation.
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1.6.5.4 Binary to Hexadecimal / Hexadecimal to Binary
To convert from binary numbers to hexadecimal, we partition the binary number into
groups of 4 digits (from right to left), and pad it with zeros if the number of digits is not
divisible by 4. We then convert each partition into its corresponding hexadecimal digit.
The following is a table showing the binary representation of each hexadecimal digit.
Hexadecimal
Digit
Binary
Representation
0 0000
1 0001
2 0010
3 0011
4 0100
5 0101
6 0110
7 0111
8 1000
9 1001
A 1010
B 1011
C 1100
D 1101
E 1110
F 1111
Table 6: Hexadecimal Digits and their corresponding binary represenation
For Example:
11111102 = ? 16
0 1 1 1 1 1 1 0
7 E
Equivalent Hexadecimal
number
Converting hexadecimal numbers to binary is just the opposite of what is given above.
Simply convert each hexadecimal digit into its binary representation (given the table)
and concatenate them. The result is the binary representation.
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1.7 Exercises
1.7.1 Writing Algorithms
Given the following set of tasks, create an algorithm to accomplish the following tasks.
You may write your algorithms using pseudocodes or you can use flowcharts.
1. Baking Bread
2. Logging into your laboratory's computer
3. Getting the average of three numbers
1.7.2 Number Conversions
Convert the following numbers:
1. 198010 to binary, hexadecimal and octal
2. 10010011012 to decimal, hexadecimal and octal
3. 768 to binary, hexadecimal and decimal
4. 43F16 to binary, decimal and octal
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2 Introduction to Java
2.1 Objectives
In this section, we will be discussing a little bit of Java history and what is Java
Technology. We will also discuss the phases that a Java program undergoes.
At the end of the lesson, the student should be able to:
• Describe the features of Java technology such as the Java virtual machine, garbage
collection and code security
• Describe the different phases of a Java program
2.2 Java Background
2.2.1 A little Bit of History
Java was created in 1991 by James Gosling et al. of Sun Microsystems. Initially called
Oak, in honor of the tree outside Gosling's window, its name was changed to Java
because there was already a language called Oak.
The original motivation for Java was the need for platform independent language that
could be embedded in various consumer electronic products like toasters and
refrigerators. One of the first projects developed using Java was a personal hand-held
remote control named Star 7.
At about the same time, the World Wide Web and the Internet were gaining popularity.
Gosling et. al. realized that Java could be used for Internet programming.
2.2.2 What is Java Technology?
2.2.2.1 A programming language
As a programming language, Java can create all kinds of applications that you could
create using any conventional programming language.
2.2.2.2 A development environment
As a development environment, Java technology provides you with a large suite of
tools: a compiler, an interpreter, a documentation generator, a class file packaging tool,
and so on.
2.2.2.3 An application environment
Java technology applications are typically general-purpose programs that run on any
machine where the Java runtime environment (JRE) is installed.
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2.2.2.4 A deployment environment
There are two main deployment environments: First, the JRE supplied by the Java 2
Software Development Kit (SDK) contains the complete set of class files for all the Java
technology packages, which includes basic language classes, GUI component classes,
and so on. The other main deployment environment is on your web browser. Most
commercial browsers supply a Java technology interpreter and runtime environment.
2.2.3 Some Features of Java
2.2.3.1 The Java Virtual Machine
The Java Virtual Machine is an imaginary machine that is implemented by emulating
software on a real machine. The JVM provides the hardware platform specifications to
which you compile all Java technology code. This specification enables the Java software
to be platform-independent because the compilation is done for a generic machine
known as the JVM.
A bytecode is a special machine language that can be understood by the Java Virtual
Machine (JVM). The bytecode is independent of any particular computer hardware, so
any computer with a Java interpreter can execute the compiled Java program, no matter
what type of computer the program was compiled on.
2.2.3.2 Garbage Collection
Many programming languages allows a programmer to allocate memory during runtime.
However, after using that allocated memory, there should be a way to deallocate that
memory block in order for other programs to use it again. In C, C++ and other
languages the programmer is responsible for this. This can be difficult at times since
there can be instances wherein the programmers forget to deallocate memory and
therefor result to what we call memory leaks.
In Java, the programmer is freed from the burden of having to deallocate that memory
themselves by having what we call the garbage collection thread. The garbage
collection thread is responsible for freeing any memory that can be freed. This happens
automatically during the lifetime of the Java program.
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2.2.3.3 Code Security
Code security is attained in Java through the implementation of its Java Runtime
Environment (JRE). The JRE runs code compiled for a JVM and performs class loading
(through the class loader), code verification (through the bytecode verifier) and finally
code execution.
The Class Loader is responsible for loading all classes needed for the Java program. It
adds security by separating the namespaces for the classes of the local file system from
those that are imported from network sources. This limits any Trojan horse applications
since local classes are always loaded first. After loading all the classes, the memory
layout of the executable is then determined. This adds protection against unauthorized
access to restricted areas of the code since the memory layout is determined during
runtime.
After loading the class and layouting of memory, the bytecode verifier then tests the
format of the code fragments and checks the code fragments for illegal code that can
violate access rights to objects.
After all of these have been done, the code is then finally executed.
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2.2.4 Phases of a Java Program
The following figure describes the process of compiling and executing a Java program.
The first step in creating a Java program is by writing your programs in a text editor.
Examples of text editors you can use are notepad, vi, emacs, etc. This file is stored in a
disk file with the extension .java.
After creating and saving your Java program, compile the program by using the Java
Compiler. The output of this process is a file of Java bytecodes with the file extension
.class.
The .class file is then interpreted by the Java interpreter that converts the bytecodes
into the machine language of the particular computer you are using.
Task Tool to use Output
Write the program Any text editor File with .java extension
Compile the program Java Compiler File with .class extension
(Java bytecodes)
Run the program Java Interpreter Program Output
Table 7: Summary of Phases of a Java Program
Introduction to Programming I 28
Figure 2.1: Phases of a Java Program
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3 Getting to know your Programming
Environment
3.1 Objectives
In this section, we will be discussing on how to write, compile and run Java programs.
There are two ways of doing this, the first one is by using a console and a text editor.
The second one is by using NetBeans which is an Integrated Development
Environment or IDE.
At the end of the lesson, the student should be able to:
• Create a Java program using text editor and console in the Linux (Ubuntu Dapper)
environment
• Differentiate between syntax-errors and runtime errors
• Create a Java program using NetBeans
3.2 Introduction
An IDE is a programming environment integrated into a software application that
provides a GUI builder, a text or code editor, a compiler and/or interpreter and a
debugger.
This tutorial uses Ubuntu Dapper as the operating system. Make sure that before you do
this tutorial, you have installed Java and NetBeans in your system. For instructions on
how to install Java and NetBeans, please refer to Appendix A. For the Windows XP
version of this section, please refer to Appendix B.
Before going into details, let us first take a look at the first Java program you will be
writing.
3.3 My First Java Program
public class Hello
{
/**
* My first java program
*/
public static void main(String[] args) {
//prints the string "Hello world" on screen
System.out.println("Hello world!");
}
}
Before we try to explain what the program means, let's first try to write this program in a
file and try to run it.
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3.4 Using a Text Editor and Console
For this example, we will be using a text editor to edit the Java source code. You will also
need to open the Terminal window to compile and execute your Java programs.
Step 1: Start the Text Editor
To start the Text Editor in Linux, click on Applications->Accessories->Text Editor.
Step 2: Open Terminal
To open Terminal in Linux, click on Applications-> Accessories-> Terminal.
Introduction to Programming I 30
Figure 3.1: Text Editor Application in Linux
Figure 3.2: Terminal in Linux
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Step 3: Write your the source code of your Java program in the Text Editor
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Figure 3.3: Writing the Source Code with the Text Editor
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Step 4: Save your Java Program
We will save our program on a file named "Hello.java", and we will be saving it inside a
folder named MYJAVAPROGRAMS.
To open the Save dialog box, click on the File menu found on the menubar and then
click on Save.
After doing the procedure described above, a dialog box will appear as shown in Figure
below.
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Figure 3.4: Save As Dialog
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Click on the browse button, and then click on the Create Folder button.
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Name the new folder MYJAVAPROGRAMS. Now, click on the MYJAPROGRAMS folder in
order to get inside that folder. You will see a similar figure as shown below after you
clicked on MYJAVAPROGRAMS. The folder should be empty for now since it's a newly
created folder and we haven't saved anything in it yet.
Now, in the Selection textbox, type in the filename of your program, which is
"Hello.java", and then click on the SAVE button.
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Now that you've saved your file, notice how the title of the frame changes from "Untitled
Document 1 (modified) – gedit" to "Hello.java (~/MYJAVAPROGRAMS) - gedit". Take
note that if you want to make changes in your file, you can just edit it, and then save it
again by clicking on File -> Save.
Introduction to Programming I 35
Figure 3.5: New Window After Saving
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Step 5: Compiling your program
Now, the next step is to compile your program. Go to the Terminal window we just
opened a while ago.
Typically, when you open the terminal window, it opens up and takes you directly to
what is called your home folder. To see what is inside that home folder, type ls and
then press ENTER. What you wi