1. Getting Started

What We Will Cover 1.1: Course Information Introductions: Name, why taking this course, claim to fame Contact Information Syllabus Schedule Class Expectations Course Web Pages Site Search College Regulations Using WebCT Roll Call Exercise 1.1: Course Questions 1.2: Succeeding in This Course 1.2.1: Elements of Success 1.2.2: Using the CTC for Homework Assignments 1.2.3: Can I Run This On My Own Computer? 1.2.4: Summary Exercise 1.2 1.3: Introduction to Java 1.3.1: History of Java 1.3.2: Java Environment 1.3.3: Java Compared to C++ 1.3.4: How Java Compiles and Interprets Code 1.3.5: Summary Exercise 1.3 1.4: Editing, Compiling and Running Java Programs 1.4.1: Writing, Editing and Saving Source Code 1.4.2: Compiling and Running Programs 1.4.3: Summary Exercise 1.4 1.5: Language Building Blocks 1.5.1: Comments and Whitespace 1.5.2: Identifiers and Keywords 1.5.3: Literals 1.5.4: Classes and main Methods 1.5.5: Summary Exercise 1.5 Wrap Up Assignments Due By Next Meeting: A1: Information Please! (9/10/03) Lab Exercise 1.1 Instructions Use the next 5 minutes to complete the following. Join a group of 3-4 people and prepare an answer to one of the following questions. Select one member from your group as a representative to describe your answer to the class. Exercise Questions How do you plan to balance the work required by this course with the other activities in your life? What can you hope to learn by the time you complete this course? How can someone locate information in the course web pages? ^ top 1.2: Succeeding in This Course Objectives At the end of the lesson the student will be able to: Describe how to study effectively for this course Use computers in the CTC for homework Install software used in this course at home ^ top 1.2.1: Elements of Success Main purpose of grading is to motivate you to learn the course material Secondary purpose is to evaluate how well you completed the course work Not the same as how well you know the material Also must complete the course work on time Can look at the grading policies to analyze what must be done to succeed Homework Assignments Homework designed to have you apply the lecture concepts in more detail Also designed to have you explore ideas in more depth If you get stuck: Read the textbook Contact the instructor Submit homework to WebCT at least the day before it is due Even if you are not done, turn it in Get credit for what you did complete Make sure to state an accurate status in the README.txt file Note that homework deadlines are real -- late homework is not accepted Most homework has extra credit possibilities Exams, Tests and Quizzes Skim through the lecture notes and write a question for each section For example, in this section I might write a question like: How should students prepare for a test? Most times, your question and mine will be close enough for you to answer the question correctly Similarly, review the assigned reading Since exams have programming problems, also review your programming assignments. A few more tips: I avoid using true/false questions Most questions should start with "How" or "Why" rather than "What" Questions starting with "What" are used for definitions I try to use questions containing actual code ^ top 1.2.2: Using the CTC for Homework Assignments First you will need a login and password You can use either Linux, Macintosh or Windows computers for your assignments For more information, follow the link to the CTC homepage ^ top 1.2.3: Can I Run This On My Own Computer? All the technology we use runs on most any computer Instructions for installing Java available from the HowTo's page ^ top 1.2.4: Summary Four elements to success in this course Do your homework assignments and turn them in on time Prepare for the homework quizzes and complete them on time Prepare for the midterm and complete it on time Prepare for and attend the final exam Can complete homework assignments in the CTC Can also install the necessary software at home or work ^ top Exercise 1.2 Take one minute to write one quiz-question for the information we just covered. ^ top 1.3: Introduction to Java Objectives At the end of the lesson the student will be able to: Describe how Java compares with C++ Name and describe three types of programs you can create with Java Explain how a virtual machine helps Java achieve platform independence ^ top 1.3.1: History of Java 1990 - "Green" project started at Sun Java originally called Oak Developed for digitally controlled consumer devices and computers 1991 - Java created by James Gosling, Sun Microsystems, Inc. Inspired by? 1992 - "Green" project finished 1992 - 1994 - Tried to turn "Green" technology into products Failed But then the Internet happened... 1996 - Official launch of JDK 1.0 Primary focus was Applets 1997 - Sun releases JDK 1.1 1998 - Sun releases SDK 1.2 Now called the Java Platform 2000 - Sun releases SDK 1.3 2002 - Sun releases SDK 1.4 Today a general-purpose programming language used extensively More information Java Technology: An Early History The Java Platform: Five Years in Review ^ top 1.3.2: Applications, Applets and Servlets What is java used for today? Applications Applications are programs that perform specific functions for users Wordprocessors Spreadsheets Drawing programs One example: jEdit Text editor written in Java Most modern applications use a Graphical User Interface (GUI) Java provides a complete set of APIs for programming GUIs Will use GUIs in second half of the course Example of GUI application program you will develop in this course: Applets Applet: a Java program that runs in a browser Original impetus for Java was applets Two famous applets captured the attention of Netscape Molecule Viewer SortDemo Web-Based Applications Web applications are programs that perform specific tasks for the Web Java is the dominant programming language for developing these applications Java provides special server-side application known as a servlet Examples of Web-base applications: Web servers such as Apache Tomcat Web services: different applications communicating via open APIs We will write a web browser and web application toward the end of the course More Information Demonstration Applets and Applications Servers and Engines ^ top 1.3.3: Java Compared to C++ Syntax intentionally similar to C++ Easy for C++ programmers to move to Java Has several important advances over C++ All programs are encapsulated in classes "Pure" object-oriented language OOP improves programmer productivity (>2X) Automatic memory management ("garbage" collection) Improves memory management and reliability More intelligent use of pointers (references) No pointer arithmetic Simpler model Less error prone and more reliable Build-in bounds checking of arrays Helps prevent buffer overflow Buffer overflows are one of the leading causes of computer vulnerabilities Built-in support for multithreading Large class-libraries Known as APIs (Application Programming Interfaces) Runs without recompiling on many operating systems and hardware platforms Uses a virtual machine Fastest Java runs slightly slower than fastest C++ Originally about 10x slower, now about 2x with "Hotspot" compiler Compilers exist to translate directly to native machine code (GCJ) Lose portability when compiled Note that Java is usually faster than MS Visual C++ ^ top 1.3.4: How Java Compiles and Interprets Code Three steps to creating a Java program: Editing Write program source code using any text editor Save source code on file system or network Source code files have .java suffix Compilation Use a compiler to translate the source code to bytecodes Files with translated bytecodes have .class suffix Execution Use java interpreter program to run the bytecodes Class Loader: moves bytecodes from file system or network into memory Bytecode Verifier: tests bytecodes to establish safety and security Interpreter (JVM): translates bytecodes into machine language Java Virtual Machine (JVM) makes "write once, run anywhere" possible More Information The Java Language Environment ^ top 1.3.5: Summary Java used to develop many types of programs including: Applications: programs that perform specific functions for users Applets: a Java program that runs in a browser Servlet: server-side application Java often compared to C++ Similar syntax Automatic memory management (not in C++) Better model for using pointers (references) Built-in support for multithreading Runs slightly slower than C++ Java programs require three steps: Created with an editor (or IDE) Compiled to bytecode using a compiler Executed using a JVM ^ top Exercise 1.3 Take one minute to write one quiz-question for the information we just covered. ^ top 1.4: Editing, Compiling and Running Java Programs Objectives At the end of the lesson the student will be able to: Compile and run Java programs, given the source code Display program output to the command line Developing Java code consists of three steps Writing the source code Compiling the source code to bytecode Executing (running) the program This process is repeated many times during development ^ top 1.4.1: Writing, Editing and Saving Source Code Can use most any text editor to write and save Java source code Windows: Notepad, WordPad, Textpad Linux can use VIM, gedit, pico, ... Mac: SimpleCap, ... Must make sure to save the file using the four-letter extension: java About Using IDEs Many Integrated Development Environments (IDEs) available for Java Typically provide visual tools for designing forms and debugging code I do not recommend using an IDE while learning Java IDE will generate code for you, which does not help you learn IDEs are complex tools that themselves are difficult to learn Can distract you from your goal of learning Java I do recommend using IDEs once you have a good understanding of Java Easier to develop user interfaces Improves programmer productivity Any program you submit must run from the command line Sample Program: Hello World Example program we can save as a source code file public class HelloWorld { public static void main(String[] args) { System.out.println("Hello, world!"); } // end method main } // end class HelloWorld Copy this into a text editor so we can save it Next step is to compile and run the program ^ top 1.4.2: Compiling and Running Programs Compiling Source Code Open a window with a command prompt Change directory (cd) to where program source code is stored Type: javac HelloWorld.java If no errors, creates HelloWorld.class Running a Program Type: java HelloWorld Interpreter loads .class file for HelloWorld Note that .class suffix is not typed Interpreter calls the main method by default Using Text Editors Many text editors have provision for compiling within the editor Textpad: Tools menu jEdit: Press the java and javac tabs More Information Use a Windows Console: instructions on using a DOS console on Windows. ^ top 1.4.3: Summary You can use most any text editor for writing and editing source code To compile an application, use the javac command To run an application, use the java command Many text editors provide features to make it easier to compile and run programs Once you have mastered the basics of Java, you should use an IDE While you are learning, it is better to use a text editor ^ top Exercise 1.4 Take one minute to write one quiz-question for the information we just covered. ^ top 1.5: Language Building Blocks Objectives At the end of the lesson the student will be able to: Use comments and whitespace in programs Identify Java keywords Make up valid identifiers Use literals in programs Like all programming languages, Java has grammar rules Rules specify how a correct syntactic structure can be formed from the words and numbers that make up a program Grammar also has a semantic definition specifying the meaning of syntactically correct code ^ top 1.5.1: Comments, Statements and Whitespace Comments Comments are ... comments -- notes to people reading the code Comments ignored by compiler Use comments to document and describe code Comments can start with // and last to end of the line // this is a comment Comments can span multiple lines: /* ... */ /* This is a multi-line comment which can be split over many lines or a portion of one line. */ Javadoc Comments Javadoc utility uses these types of comments to automatically create program documentation Javadoc comment is made up of two parts with a blank line (containing a single asterisk "*") between sections Description of the code Followed by zero or more tags /** * Description part of a Javadoc comment * * @tag Comment for the tag */ Starts with the begin-comment symbol: /** Last line begins with the end-comment symbol */ Notice that the asterisks line up (by convention) Use Javadoc comments before every class and function of your programs More information: How to Write Doc Comments for the JavadocTM Tool For a list of tags: Tag Conventions Important in your Java assignments: Document Java Assignments Statements Statements direct the operation of the program Most statements end in a semicolon (;) However, statements within a set of braces {} end with a right brace Whitespace Whitespace: blank lines, spaces, and tabs Whitespace ignored by compiler Use whitespace to make programs more readable ^ top 1.5.2: Identifiers and Keywords Identifier - the name of something (e.g. variable, object, method or file) used in a program. Purpose of an identifier is to provide a name for something Should always try to make the name meaningful Programmers create identifiers for the names of many things in a program: classes variables methods Identifiers are made up of a sequence of characters Each character can be a: Letter Digit Connecting punctuation (e.g. underscore _) Currency symbol (e.g. $, ¢, £, ¥) Can not start with a digit Can not contain any periods or spaces Can not be a keyword (e.g. "if, "for", etc.: see Java Language Keywords) Are cAsE sEnSiTiVe! id, ID, iD and Id are all valid but different identifiers Identifiers have naming conventions: Use meaningful names Use only letters and digits Start class names with an uppercase letter Start variable and method names with a lowercase letter Capitalize interior words in multi-word names (e.g. myAge) Keywords Keywords are reserved words with predefined meanings We used keywords in our HelloWorld program public class static void public class HelloWorld { public static void main(String[] args) { System.out.println("Hello, world!"); } // end method main } // end class HelloWorld All keywords have special meaning in Java Can only be used for their specified purpose Attempting to use for any other purpose will generate a compiler error Thus cannot use keywords for identifiers For a current list, see Java Language Keywords ^ top 1.5.3: Literals Strings of characters that represent "literal" data values Treated as a constant (i.e. unchanging) value in a program Examples of literals: Integer: int x = 123; Floating-point: double x = 1.23; Character: char x = '1'; Boolean: boolean x = true; String: String x = "123"; ^ top 1.5.4: Classes and main Methods Return to our example program we saved as a source code file public class HelloWorld { public static void main(String[] args) { System.out.println("Hello, world!"); } // end method main } // end class HelloWorld Declaring a class When you develop a Java program, you code one or more classes for it Each class starts with a declaration like the following: public class HelloWorld { // class definition goes here } Keyword public means all parts of the program can use this class Keyword class tells compiler that a class is being defined Left brace { begins body of every class Likewise, right brace } ends body of every class Any code between the curly braces is called the class definition Declaring a main Method Every Java program has one or more methods Methods are blocks of code that perform a task Similar to functions in other programming languages public static void main(String[] args) { Every Java application must have a method called main Applications begin executing at main method Keyword public allows any program to use the main method in this class void means main has no return value args is a parameter of type String[] -- cover later For now, mimic the first line of main Left brace { begins body of every method Right brace } ends body of every method Using Methods and Variables Inside Classes and Objects Recall the line: System.out.println("Hello, world!"); System.out refers to the out variable in the System class Can refer to variables and methods inside a class Join the class name and name of the method or variable separated by a period (".") Similarly, out.println() refers to the println method of the out object For objects, join the object name with the method or variable separated by a period (".") Will cover this in more detail later in the course ^ top 1.5.5: Summary Comments help document what a program does Useful for humans to read Java has three styles of comments // /* ... */ /** ... */ Statements direct what a program does Use whitespace to make programs more readable Identifiers are any name you create in a Java program Keyword is a special word reserved by Java Literals are strings of characters the represent constant data values You develop Java programs writing one or more classes Every Java application starts with a main method ^ top Exercise 1.5 Take one minute to write one quiz question for the information we just covered. ^ top Wrap Up Due Next Class: A1: Information Please! (9/10/03) ^ top Home | WebCT | Announcements | Schedule | Expectations | Syllabus Help | FAQ's | HowTo's | Links Last Updated: September 10 2003 @16:43:41