2. A Visit to the United Nations At the UN some 200 different languages are spoken. To illustrate the complex task of allowing all of the world leaders to communicate, the example on the next slide simply shows 12 world leaders.

3. President Bush United States English Spanish President Great Brittan English Prime Minister President Putin Russia Russian President Rau Germany German President Ciampi Italy Italian President Schirac France French President Fox Mexico Spanish President Zemin China Chinese Prime Minister Balkenende Holland Dutch President Mbeki South Africa Afrikaans Prime Minister Koizumi Junichirp Japan Japanesse For example: President Bush would need different translators for Dutch, German, Spanish, French, Italian, Russian, Chinese, Japanese, and Afrikaans.

4. President Bush United States English Spanish President Great Brittan English Prime Minister President Putin Russia Russian President Rau Germany German President Ciampi Italy Italian President Schirac France French President Fox Mexico Spanish President Zemin China Chinese Prime Minister Balkenende Holland Dutch President Mbeki South Africa Afrikaans Prime Minister Koizumi Junichirp Japan Japanesse With 200 world leaders, if we want to be able to translate instantly (as in one single step) from any language to any other language about 20,000 translators would be needed.

5. President Bush United States English Spanish President Great Brittan English Prime Minister President Putin Russia Russian President Rau Germany German President Ciampi Italy Italian President Schirac France French President Fox Mexico Spanish President Zemin China Chinese Prime Minister Balkenende Holland Dutch President Mbeki South Africa Afrikaans Prime Minister Koizumi Junichirp Japan Japanesse The solution is not to try to translate in one step, but to allow the translation to occur in 2 steps. Every world leader brings one translator that knows their native language, and English.

6. President Bush United States English Spanish President Great Brittan English Prime Minister President Putin Russia Russian President Rau Germany German President Ciampi Italy Italian President Schirac France French President Fox Mexico Spanish President Zemin China Chinese Prime Minister Balkenende Holland Dutch President Mbeki South Africa Afrikaans Prime Minister Koizumi Junichirp Japan Japanesse Translator

7. What does the UN have to do with Java? MAC InterpreterCompaq InterpreterHP Interpreter Compiler

8. Platform Independence A programming language is considered platform independent or portable if program source code created on one type of computer platform can execute on another computer platform without any difficulty.

9. Bytecode Bytecode is a low level-level code file that cannot execute as a regular machine code file. Bytecode is understood, and executed, by a Java interpreter, called a Java Virtual Machine (JVM).

10. Java Uses a Compiler AND an Interpreter Java uses a compiler to translate the program source code created by the programmer into bytecode. Java then continues and uses an interpreter to translate the bytecode into executable machine code line by line.

11. Applet or Application? A Java program designed to operate inside a web page is called an applet. A Java program designed to operate in a stand-alone environment is called an application.

12. The Basic Java Tools A text editor to write Java program source code A compiler to translate source code into bytecode An interpreter to translate and execute bytecode

26. Downloading JCreator JCreator 3.50 LE is FREEWARE distributed and copyrighted by Xinox Software. This means you can download it at home for free to work on your Java assignments. The next few slides will demonstrate the downloading process:

28. If you have not already downloaded the JDK, you can do it from here. This is the one you want.

29. JCreator has a new system where you are required to provide an email address and then they will email you the download link.

32. NOTE: After saving JCreator is NOT yet installed! All you have done is to download a zipped file that must still be extracted and installed.

39. This is probably the most important step! (And unfortunately the step that people mess up the most!) You must specify the directory where the JDK has already been installed. The author chose the default shown below.

40. These 2 windows are not needed. Click the [x] to close each one.

42. If you have difficulty seeing small letters on the screen, you can adjust the font and size of the text here. Click [Configure] -- [Options] -- [+] of Java -- [Font]

43. Click [Configure] -- [Options] -- [Workspace] (not the [+]) Remove all the checks in the Workspace window and click OK.

45. The Programs in this Chapter There are 11 programs in this chapter. The first 5 program, Java0201 - Java0205 are meant just to show the process of compiling and executing Java applications and Applets. The actual code in these examples is not important at this time. Programs Java0206 - Java0211 show the introductory Java commands explained in this chapter. The code is very important in these program examples.

48. Remember to Re-Compile! After any change to a program, no matter how small, you must recompile the program before testing the execution!

49. Wrong Way to Execute an Applet While compiling an applet is the same as compiling an application, the actual executing of an applet is different.

50. Two Ways to Run an Applet Use a web browser and load the HTML file that includes the Java applet. Load the HTML file in JCreator and execute that instead of the.java file.

53. Windows 2000/XP Notice The graphics display of program Java0203 may only show diagonal lines when you try it on a computer running Windows 2000 or Windows XP. Move your mouse slightly and the other lines will show up. This does not appear to happen with later versions of Windows XP.

54. College Board View on Input/Output 11. User input is not part of the AP Java subset. There are many possible ways for supplying user input; e.g., by reading from a BufferedReader that is wrapped around System.in, reading from a stream (such as a file or an URL), or from a dialog box. 12. Testing of output is restricted to System.out.print and System.out.println. As with user input, there are many possible ways for directing the output of a program, for example to System.out, to a file, or to a text area in a graphical user interface.

56. A Note About Warning Notes The messages after Note: are NOT error messages that will prevent a program from compiling and executing. These Note: messages are warnings.

57. Frozen Images of Java0205

58. // Java0206.java // This program demonstrates text output with println. // Note how the file name, Java0206, is the same as the // class identifier Java0206. // Make sure that you observe "case-sensitivity". public class Java0206 { public static void main (String args[]) { System.out.println("Plain Simple Text Output"); }

59. Java Keywords and Program Statements A Java keyword is a word that has a special meaning in the program or performs a special function. One or more keywords combine to make a program statement. Keywords in Java are case-sensitive. This means that print is a Java keyword, which is not the same as Print.

60. // Java0207.java // This program demonstrates // how to display four lines of text // using the keyword. public class Java0207 { public static void main(String args[]) { System.out.println("Line 1"); System.out.println("Line 2"); System.out.println("Line 3"); System.out.println("Line 4"); }

61. // Java0208.java // This program demonstrates the // difference between and //. The // command adds a "line feed" // after the output display. public class Java0208 { public static void main(String args[]) { System.out. print ("Line 1"); System.out. print ("Line 2"); System.out.println("Line 3"); System.out.println("Line 4"); }

62. // Java0209.java // This program shows how to skip a line between statements. // Using with empty parentheses will generate // a carriage-return/line-feed. public class Java0209 { public static void main (String args[]) { System.out.println("Text Output on Line 1"); System.out.println(); System.out.println("Text Output on Line 3"); }

63. System.out.print & System.out.println Both keywords println and print generate an output display of characters contained between double quotes. Both println and print follow keywords System.out. println("Java is an island in Indonesia.") will display: Java is an island in Indonesia. print("Java is an island in Indonesia.") will also display: Java is an island in Indonesia. The keyword println generates display followed by a carriage- return/linefeed (crlf). The keyword print generates display without a crlf. The statement System.out.println(); generates a crlf, meaning skip a line, without any other display.

64. // Java0210.java // This program demonstrates that the file name of a program // and the public class name must be identical. // This program will not compile. public class Boohiss { public static void main (String args[]) { System.out.println("The bytecode file name"); System.out.println("will be the same as the"); System.out.println("public class identifier."); }

65. File Names and Class Names The external file name of your program needs to be identical to the public class name inside your program, minus the java extension. For example: If you use public class Howdy in your program then you need to save the program with Howdy.java.

66. // Java0211.java // This program has an intentional mistake. // The output window indicates an error and the program does not execute. // Many error messages provide important clues to help fix the problem. public class Java0211 { public static void main (String args[]) { System.out.println("In English..."); System.out.println("Every sentence ends with a period (.)"); System.out.println("In Java...") System.out.println("Every statement ends with a semicolon (;)"); }

67. // Template.java // This program does not display any text, nor does it // process any information. // It is a template for an application, text-output, program. public class Template { public static void main (String args[]) { // The comments need to be replaced with // program statements that process and // display information. }

68. Important Template Program Points  Comments are optional in any program, including your templated program.  Start your program with the program statement: public class  In the example the class identifier is Template, which is not a required name.  Use the four braces as shown in the example.  Use the following statement exactly as shown: public static void main (String args[])  Write the program code that you create between the inner braces, replacing the comments.

69. Identifier Rules Identifiers can use alpha-numeric characters and the underscore character. External file names can start with any legal character. However, class identifiers, which must match the external file name must start with an alpha character.

70. Java Keywords  Reserved Words  Pre-defined Java Identifiers  User-defined Identifiers

71. The 3 Steps of a Java Program 1.Write the Java source in some text editor. The source code file must end with.java. 2.Translate the source code file with a Java compiler into an intermediate bytecode file that will end with.class. 3.Execute the bytecode file with a Java Virtual Machine (JVM) program, which is an interpreter. Note: All three of these steps can be done with a text editor and the command prompt or an Integrated Development Environment (IDE), like JCreator.

73. Protect Your Computer From the Environment Computers and computer information are vulnerable. Computers can be physically damaged. RAM is temporary, save often! Disk, CDs and even hard drives can go bad. Back up your stuff! Blackouts and Power Surges are major problems. Backup Batteries and Surge Protectors are useful.

74. Protect Your Computer From Viruses A virus is a special program that has these two qualities: The ability to duplicate itself to spread to other systems. The payload it carries, which is a program that will do some type harm to the computer.

75. Protect Your Computer From Improper Access Don't leave your computer unattended and logged in. Information can easily be copied or erased from an unattended computer. Unattended laptops are easily stolen. Label and guard your stuff!

76. The Ethical Use of Computer Software Copying copyrighted software is illegal. Companies have been sued and people have been arrested for not taking this seriously.

77. Hacking Some confused people think that if you hack into a network, it is fine as long as you don't steal any money or damage any information. Just attempting to hack into a network is a misdemeanor. If you actually succeed at getting in, you have already committed a felony. Yes, high school students have been prosecuted for this!

78. Vandalism Physical computer vandalism is bad, but typically not a problem in high school. You also need to make sure you do not alter ANY settings on the computer or install ANY software unless directed to do so by your teacher. Altering settings can prevent the computer from working properly. Downloading software has legal issues and can also cause the spread of viruses.