Programming and Databases

Transcription

1

2 Programming and Databases SECOND EDITION Joy T. de Jesus, Jr. Lesley Abe, M.S. Ma. Sheila A. Magboo, M.S. Vincent Peter C. Magboo, M.D., M.S. Jaime D.L. Caro, Ph.D. i

3 Trademark of TechFactors Inc. by TechFactors Inc. All rights reserved. No part of this courseware may be reproduced or copied in any form, in whole or in part, without written consent of the copyright owner. Fourth printing of the second edition, 2015 ISBN Published by TechFactors Inc. Printed in the Philippines Authors Joy T. de Jesus, Jr., Lesley Abe, M.S., Ma. Sheila A. Magboo, M.S., and Vincent Peter C. Magboo, M.D., M.S. Series Editor Jaime D.L. Caro, Ph.D. Cover Design Gilbert Lavides Content and Editorial Alvin Ramirez, Frances Ibañez, M.A., and Alexander Lim, MBA Creatives Jiyas Suministrado, Gilbert Lavides, and Regina Zapata Systems Kim Benebese, Caseylyn Dionisio, and Mark Abliter Exclusively distributed by TechFactors Inc. 101 V. Luna Road Ext., Sikatuna Village Diliman, Quezon City 1101 Philippines Telephone number: (632) address: Website: I.C.Topia is an independent publication and has not been authorized, sponsored, or otherwise approved by Microsoft Corporation or any company stated herein. All other trademarks are registered trademarks of their respective companies. ii

4 FOREWORD The difference between high school students who are introduced to practical computing proficiencies and those who are not is their capacity to carry-over what they ve learned about information technology into college and consequently apply them, resulting in more productivity inside and outside of the school environment. The TechFactors I.C.Topia courseware series gives high school students the means to make this happen with the use of the Department of Education (DepEd) curriculum. The I.C.Topia courseware is a complete system for learning specific skill sets in relation to popular productivity applications used at home, the office, and in school. Such programs both proprietary and open source have been selected and highlighted in the series of books as integrated subjects in the lessons. Each I.C.Topia book title is carefully chosen for its relevance to current trends of use. They combine applications and defined output processes specifically for their related aspects of use. Word processing, desktop publishing, and office applications are the basis for the office productivity courseware; Web development and javascripting are used for the Internet learning set; programming and database are taken up in the software development kit; and lastly, digital photography, videography, and project management comprise the multimedia production book. As a server- and Internet-based courseware series, I.C.Topia gives the benefit of onthe-go-learning that s relevant in today s interconnected world. It serves to develop practical know-how and adeptness in using networks during the skills-mastery process. I.C.Topia serves to produce productive graduates in a country that grows to be more technologically-dependent, connected, and conscious of projecting it s presence to the rest of the world. Jaime D.L. Caro, Ph.D. Series Editor iii

5 ABOUT THE AUTHORS Joy T. de Jesus, Jr. is currently working as a full-time anlayst/programmer at Rizal Commercial Banking Corporation. He specializes in ATM-based and ATM-related systems. He has served as trainer and content developer of Techfactors Inc., co-authoring the following books: Office Productivity, IT Project Management, Java Programming By Example, Animation in a Flash, and C++ Programming Fundamentals. He studied Computer Science major in Software Technology at De La Salle University and pursued further studies at Mapua Information Technology Center. Lesley Abe, M.S. holds a Master of Science in Computer Science degree from De La Salle University and graduated cum laude with a Bachelor in Information Technology from the Polytechnic University of the Philippines. She is an experienced educator in Computer Science and Information Technology. She now works parttime as faculty of De La Salle University Main College of Computer Studies and is also an IT consultant for various companies. Prof. Ma. Sheila A. Magboo, M.S. is an Assistant Professor at the Mathematical and Computing Sciences Unit, Department of Physical Sciences and Mathematics, University of the Philippines Manila where she teaches file processing, database systems, software engineering, systems analysis and design, introduction to bioinformatics, among others, both at the undergraduate and graduate level. She has also handled several short courses at UPITTC and served as guest lecturer at TechFactors on several occasions. She is currently Program Manager of a research project named Virholex or Virus-Host Interaction Lexicon, a comprehensive information system envisioned for use by research groups studying virus-host interaction dynamics with a systems biology approach. Sheila earned her BS Mathematics degree at the University of the Philippines Manila and her MS Information Technology at De La Salle University. Her current research interest is on the development of web-based applications in the field of systems biology and bioinformatics. Dr. Vincent Peter C. Magboo, M.D., M.S. is an Associate Professor and former Chair of the Mathematical and Computing Sciences Unit, Department of Physical Sciences and Mathematics, University of the Philippines Manila where he teaches statistics, differential equations, calculus, algebra, discrete mathematics, computer organization, software engineering, practicum, research methods, introduction to bioinformatics, among others, both at the undergraduate and graduate level. He spearheaded the institution of revisions in the existing BS Computer Science curriculum by creating two tracks, the BS Computer Science Major in Health Informatics and the BS Computer Science Major in Statistical Computing, as well as the institution of a new graduate program, the Master of Science in Health Informatics. He frequently serves as statistics consultant to medical doctors undergoing research and regularly presents posters at the National Academy of Science and Technology. He earned his BS Mathematics and Master of Statistics degree at the University of the Philippines Diliman and his Doctor of Medicine with specialization in Nuclear Medicine at the University of Santo Tomas. iv

6 ABOUT THE SERIES EDITOR Jaime D.L. Caro, Ph.D. has more than 20 years of experience in education and research in the areas of Computer Science, Information Technology, and Mathematics. He received the degrees of Bachelor of Science major in Mathematics (cum laude) in 1986, Master of Science in Mathematics in 1994, and Doctor of Philosophy in Mathematics in 1996, all from the University of the Philippines Diliman. He spent a year as a post doctorate research fellow at the University of Oxford from 1997 to He is presently Assistant Vice President for Development of the University of the Philippines, Program Director of the UP Information Technology Training Center (UP ITTC), and a professor of Computer Science in UP Diliman. He is an honorary member of the Philippine Society of Information Technology Educators (PSITE), President of the Computing Society of the Philippines (CSP), and a member of the Technical Panel on Information Technology Education of the Commission on Higher Education (CHED). Dr. Caro is a recognized expert on Complexity Theory, Combinatorial Network Theory, Online Communities, and e-learning. v

7 TABLE OF CONTENTS Lesson 01: Getting Acquainted with Java 3 Designs Goals Behind the Java Language Versions of Java Lesson 02: Understanding the Java Program 9 Programming Java with BlueJ Creating Java Programs with BlueJ Compiling Your Program Using BlueJ Executing Your Program Using BlueJ What Can Go Wrong and Some Common Programming Errors Analyzing Welcome.java Analyzing Main.java Lesson 03: Java Names and Labels 22 Java Keywords Identifiers Data Types Variables Constants Casting Lesson 04: Connecting Data Through Operators 32 Operators Operator Precedence Lesson 05: Conditions for Decisions 46 If Statement If-Else Statement Nested-If Statement Switch Statement vi

8 Lesson 06: Loops and Exceptions 56 What Are Loops? For Loop While Loop Do-While Loop Nested Loops What Are Exceptions? Error-Handling Try and Catch Statements Lesson 07: Creating Classes 70 Classes Methods Inheritance Method Overloading Overriding Lesson 08: Arranging with Arrays 89 Single-Dimensional Arrays Array of Objects Lesson 09: Introduction to Databases 97 What Is a Database? Hierarchy of Data in a Database Why Use a Database? What Is a Database Management System? Lesson 10: Introducing MySQL and phpmyadmin 104 What Is MySQL? MySQL Data Types MySQL STRING Data Type MySQL NUMERIC Data Type MySQL DATE and TIME Data Type Designing Our Sample Database: My Friends Database Lesson 11: Introducing phpmyadmin 113 What Is phpmyadmin? Creating a MySQL Database from phpmyadmin Adding Records vii

9 Editing Records Deleting Records Displaying the Contents of My Database Lesson 12: More MySQL and phpmyadmin 123 Altering the Structure of My Table Making a Backup of My MySQL Database Dropping a Database Restoring My Database from the Backup Querying My MySQL Database Lesson 13: SQL 140 What is SQL? The Data Definition Language (DDL) The Data Manipulation Language (DML) The Data Control Language (DCL) Making Our Java Programs Access a Database Lesson 14: Accessing MySQL Databases with JDBC 158 JDBC and the MySQL Connector/J Registering MySQL Connector/J in BlueJ Accessing the MySQL Database with a Simple Java Program Lesson 15: Sample Java Program Accessing a Database 172 Sample Application: Friends Database Displaying Friend Information (Display.java) Adding a New Friend (Insert.java) Lesson 16: Updating and Deleting 196 Updating a Friend s Record (Update.java) Deleting a Friend s Record (Delete.java) Conclusion Expand 210 viii

10 INTRODUCTION In this course, the student will find object-oriented programming using Java enjoyable. Basic Java concepts and principles are discussed, alongside with the explanation of sample executable programs. The student does not need prior knowledge of any programming language to understand Java. And learning Java does not end after going through this courseware. Additional information, samples, and references can be found in various resources such as the Internet. The student will also be trained in the various concepts and models necessary to store, manipulate and handle data using MySQL. This will involve creating forms and reports from queries based on data present in an existing database. LEARNING GOALS By the end of this courseware, the student is expected to: 1. Appreciate Java as a programming language. 2. Define commonly used terms in object-oriented programming such as classes and objects. 3. Apply the different language elements and constructs of Java to solve simple programming problems. 4. Create a database using MySQL through phpmyadmin. FORMATTING CONVENTIONS Italics used to distinguish filenames, directories, or class names Boldface used to indicate important terms in the lesson Courier used to represent Java syntaxes DISCLAIMER Every effort has been made to make this courseware as accurate as possible, but no warranty or fitness is implied. The authors and publishers shall have neither liability nor responsibility to any person or entity with respect to any loss or damage arising from the information contained herein. 1

11 2

12 LESSON 01 Getting Acquainted with Java Object-oriented programming ( OOP for short) was conceived to model real-world objects. In OOP, a class defines the common variables (attributes) and methods (functions) of a set of objects. An object is an instance of a class. For example, all humans have common attributes: name, age, birthday, etc.; and functions: getting old or growing up. CLASS OBJECT name Andres Bonifacio age 33 birthday November 30, 1863 At the end of this lesson, the student will be able to: 1. Compile and run a sample program in Java using an IDE. 2. Debug common errors. 3. Define classes and objects. Benefits of Java Java is simple The Java programming language was designed to make OOP easier. Once you understand how components in a program are treated as objects, you will find Java fairly simple. In addition, using other predefined and more complex components will be effortless since they are implemented and utilized in the same way. Java is reliable Java is reliable because it excludes some components that are error-prone. It also provides a way for programmers to anticipate and handle errors in their program. 3 Philippine Copyright 2009

13 Getting Acquainted with Java Java is dynamic Java makes it possible to reuse previously written programs to lessen the workload of a programmer. Aside from this, it also allows programmers to make revisions, additions, and alterations to a program without affecting other programs that might already be using it. Classes are loaded while the program is run either from your own computer, from another computer in your network, or from a computer connected to the Internet. Java is used in networking The Java language has many classes to facilitate Internet communications. Java classes can be loaded in most browsers to facilitate secure transactions over the Internet. Java is secure Java ensures that a program can go only where it was designed to go. It eliminates the possibility of altering system data unintentionally. During program execution, the Java Virtual Machine makes sure that loaded classes cannot access the file system except in the manner permitted by the client or the user. Java is free NOTE Java can be downloaded from the Internet for FREE. Just visit The sample programs in this book were compiled using J2SE SDK. We suggest that you acquire the same version to avoid getting errors due to some version differences of Java compilers. Java is portable Java codes have the filename extension.java. When compiled, a class file with.class extension is created. This file can then run on any machine which has the Java Virtual Machine, thus, making it portable. Java-enabled devices such as mobile phones are commonly used today. This means that programs developed in Java can be loaded and used in these devices. 4

14 Java code (*.java) Java Compiler bytecodes (*.class) Java Virtual Machine MAC PC UNIX Java codes written once can be executed almost anywhere. Compiling and Executing a Java Program Using an IDE In this book, BlueJ an Integrated Development Environment (IDE) that is freely available on the Internet was used to compile and run the Java applications provided. To download it, type this in your browser: NOTE Download the appropriate version depending on the computer that you have. Before you install BlueJ, check the system requirements to make sure that BlueJ can run properly on your PC. For BlueJ 1.3 and above, you need a PC with a Pentium II processor or its equivalent and 64 MB main memory. However, it is better to have a PC with a 400MHz Pentium III processor or above and 128 MB main memory for BlueJ to run smoothly. Also, you need to install J2SE or newer first before installing BlueJ. Let s use BlueJ to compile and run our Java applications: 1. Run BlueJ by double-clicking the BlueJ icon on the desktop or running it from Start > All Programs > BlueJ > BlueJ. Getting Acquainted with Java 5

15 Getting Acquainted with Java If this is your first time to run BlueJ, you will see the following screen: 2. Click Advanced so that the BlueJ window looks similar to the one below. 3. Click Browse for a specific Java Version and browse to the bin directory within your Java installation folder. Click on the file named java and click Open. 6

16 4. Click the Java version that appears and click Launch BlueJ. 5. To create a new project, click Project > New Project. 6. The New Project dialog box will appear. In the File name field, input the name of your project. Click Create. Getting Acquainted with Java 7

17 Getting Acquainted with Java 7. The BlueJ window will look similar to the following picture. Double-click this icon to open README.TXT. 8. Type the appropriate information. 9. After updating README.TXT, click Class > Close. 10. Click Edit > New Class or press Ctrl+N at the same time. 8

18 11. Type Welcome as the name of the new class then click Ok. 12. Double-click the Welcome icon to open the Welcome class. 13. Delete all the text included within the editor and type the following: //Welcome to Java public class Welcome{ public void printwelcome(){ System.out.println( Welcome to Java! ); } } 14. Click Class > Close or press Ctrl+W at the same time. Getting Acquainted with Java 9

19 Getting Acquainted with Java 15. Create another class and name it Main. Edit the Main class by double-clicking the Main icon. Delete all the text included within the editor and type the following: /* This class contains the main() method */ public class Main{ public static void main(string[] args){ Welcome Greet = new Welcome(); Greet.printWelcome(); } } Compiling Your Program Using BlueJ To compile all classes in a specific package, go to the package to be compiled and click Compile. Executing Your Program Using BlueJ 1. Right-click the Main icon and select void main(string[] args). 2. Click Ok. 3. The terminal window of BlueJ will appear to show the output. After you are done, close all BlueJ windows. 10

20 Compiling and Running Your Java Program Using the Command Prompt Your Java file, say Welcome.java, can be encoded using any plain text editor (e.g., Notepad). 1. Open Notepad from Start > All Programs > Accessories and type the Java code from Welcome.java. 2. Open another instance of Notepad and type the Java code from Main.java. 3. Save both files as Welcome.java and Main.java respectively in the bin directory within your Java installation folder. When saving in Notepad, place the filename within quotation marks. To compile our Java application using the Java Software Development Kit (SDK), we use the javac command. Go to the bin directory within your Java installation folder using the command line prompt and press Enter after typing the following: javac Welcome.java NOTE All Java files must have a.java filename extension. Java is case-sensitive. If there are no errors encountered while the file Welcome.java was compiled using the code above, then a file named Welcome.class will be created. If there are errors reported, check whether you have typed the code for Welcome.java correctly. Do the same for Main.java. javac Main.java To run our Java application, we use the java command. Press Enter after typing the following on the command prompt. java Main Observe that when compiling a Java file, we use the javac command followed by the filename and file extension of the file to be compiled. If you would like to run your Java application, then use the java command followed by the filename (without the filename extension) of the application to be run. Getting Acquainted with Java 11

21 Getting Acquainted with Java SYNTAX To compile a Java file named Welcome.java, press Enter after typing the following at the command prompt. javac Welcome.java To run a Java file named Main.java, press Enter after typing the following at the command prompt. java Main What Can Go Wrong and Some Common Programming Errors Errors encountered when you compile your application are called compile-time errors. Errors encountered during program execution are called runtime errors. Here are some compile-time errors that you may encounter: A. Line 7 is highlighted indicating that there is an error on that line, which is this: the letter w in welcome() is in lowercase. Since the Welcome class we created has a capital letter, it should be in uppercase as well. B. 12

22 Line 8 is highlighted but the error is not on line 8 but on the previous line: line 7. Apparently, line 7 has no semicolon to end the statement. There are times that the compiler may be reporting an error on a line but the real error is on another line. This kind of error reporting normally happens when a semicolon is missing at the end of a line of code. NOTE Every line of code in Java should be terminated by a semicolon (;) except for lines that include specific commands. title bar menu bar tool bar tool bar C. status bar question mark Line 5 is highlighted. It seems correct but if you look closely, the l (letter l ) in println is actually a 1 (one). When you can t figure out the error at times, the best thing to do is to retype your code. Aside from the error message on the status bar, BlueJ also provides its users with suggestions on possible causes of the detected error through dialog boxes which will appear if you click the question mark. For now, we will leave the programs we created as they are. You will be eventually taught how each command or line of code affects your programs in the next lessons. Getting Acquainted with Java 13

23 Getting Acquainted with Java Java is an object-oriented language. In this paradigm, objects are class instances. Like other object-oriented languages, you can reuse codes and create dynamic applications. Moreover, you can use its extensive builtin library to create a wide variety of programs. 14

24 Programming and Databases L1 SCORE NAME: SECTION: DATE: A. Match the Java related concepts with their corresponding meanings. 1. Java 2. Object-Oriented Programming 3. Class 4. Object a. a type of error that can be encountered during the execution of a compiled Java program b. a type of error that can be encountered while compiling your code c. these are ready-made chunks of code that can be used and reused in many applications 5. Encapsulation d. the software that executes compiled Java codes 6. Library 7. BlueJ 8. Runtime error 9. Compile-time error e. defines all the common variables and methods of a particular set of objects f. an instance of a class g. the process of combining data and function to form a class or object CUT THIS PAGE 10. Java Virtual Machine h. a programming paradigm that was conceived to model real world objects i. an object-oriented programming language that can be downloaded from for free j. a free IDE of the program discussed in this book that can be downloaded from load.html Getting Acquainted with Java 15

25 Getting Acquainted with Java B. Take a look at the following statements below. Write True on the blank provided if the statement is true, otherwise write False. 1. The Java programming language makes object-oriented programming easier. 2. Programmers should be careful in writing code for Java since it is almost impossible to anticipate and handle errors in Java programs. 3. It is possible to reuse Java classes previously written for other projects. 4. The Java Virtual Machine on your computer can load and execute Java classes stored on a different computer. 5. The Java Virtual Machine can access and modify any file on your computer. 6. Java can be downloaded from the Internet for free. 7. It is possible for a Java class compiled in a Macintosh to be executed on a PC provided that the Java Virtual Machine is properly installed. 8. The Java programming language is case-insensitive. 9. To compile a Java application using the JDK, we use the java command. 10. When a Java source code is compiled, a new file with the *.java extension will be created. 16

26 THIS IS A SAMPLE COPY To purchase the full version of this book, go to