Lab 1 Instructor: Jolanta Soltis

Check where java is installed: C:\ProgramFiles\Java\jdk1.6.0_03\bin Save your files on AFS server. Use SSH to connect or H: drive in the lab. Before you can develop an application written in the Java programming language, you will need the Java Platform Standard Edition (Java SE) development kit. It has the necessary Java Virtual Machine1 (JVM), core Application Programming Interfaces (API)s, and the compiler you'll need for most and perhaps all of your development. Note: Mac users should go to Apple's Mac OS X Java Runtime Environment. Download the JDK Download java JDK 6 Update 6: http://java.sun.com Check where java is installed: C:\ProgramFiles\Java\jdk1.6.0_03\bin J2SE 5.0 documentation: http://java.sun.com/j2se/1.5.0/download.jsp The Java Tutorial: http://java.sun.com/docs/books/tutorial

Java SE: This kit is necessary for developing all applications, except those designed for consumer devices. Java SE comes bundled with the compiler, a runtime environment, and core API. Java Platform Enterprise Edition (Java EE): This packages includes an application server, web server, J2EE APIs, support for Enterprise JavaBeans, Java Servlets API, and JavaServer Pages (JSP) technology. Use J2EE with the Java SE. Java Platform Micro Edition (Java ME): If you are interested in developing programs for Palm Pilots, screen phones, and other consumer devices, this kit provides tools for compiling, deployment and device configuration, and APIs that are specialized for each type of device. JavaFX Script Technology is a highly productive scripting language that enables content developers to create rich media and content for deployment on Java environments.

The development kits include the APIs necessary to whatever type of applications you develop in the Java programming language. Java APIs are libraries of compiled code let you add ready-made and customizable functionality to your programs to save coding time. Java programs are executed within a program called the JVM. Rather than running directly on the native operating system, the program is interpreted by the JVM for the native operating system. This is key to making your programs portable from one platform to another. In other words, you can develop your programs on a Solaris, Linux, Macintosh, or Windows, then run it on another server or platform.

Once you have the development kits you need, you are ready to begin writing code in the Java programming language. Programs are written in three basic flavors: applets, applications, and servlets/JSP pages. Applets run in the JVM built into a web browser; applications run in the JVM installed on a computer system; and servlets/JSP run in the JVM installed on a web server.

Each release of the Java 2 SDK, Standard Edition contains: Java Compiler Java Virtual Machine* Java Class Libraries Java AppletViewer Java Debugger and other tools Documentation (in a separate download bundle) 1-6

Find the directory where it was installed C:\Program Files\Java\jdk1.6.0_03\bin 1-7

PATH Do you get the following error message? Exception in thread "main" java.lang.NoSuchMethodError: main The Java runtime system needs to know where to find programs that you want to run and libraries that are needed. It knows where the predefined Java packages are, but if you are using additional packages, you must tell specify where they are located. PATH tells Java where to search for programs 1-8

Setting PATH on Windows XP The PATH variable can be set on Windows XP with the following steps. Click the Start button in the lower left of the screen. Select Control Panel from the pop-up menu. Choose System from the submenu. Click the Advanced tab. Click the Environment Variables button near the bottom and you will see two lists of variables. Look in the System variables list for a variable named PATH. If you find it, click Edit. If you don't find it, click New and enter PATH in the Variable name field. 1-9

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Compiling a Java program in DOS Create the source program with a text editor (eg, DOS, Eclipse, jEdit, TextPad, ...). DOS: Open a DOS command window and cd to the directory containing the source file. Compile the source program (Greeting.java in this example) with the following DOS command: javac Greeting.java This produces one or more ".class" files, which are the object (Java byte code) form of Java programs. You can produce a ".exe" file from this, but that isn't normally done. Run it with: java Greeting This loads the Greeting.class file and all necessary classes. 1-11

Programs to use to compile java applications: TextPad Minimum Requirements: IBM Compatible PC Microsoft Windows 95 (SP#1), NT 4 (SP#6), or later versions of Windows. COMCTL32.DLL 4.70 or later (can be downloaded from http://support.microsoft.com/default.aspx?scid=KB;en-us;q186176). 3.5MB free disk space 1. From the Configure menu, choose Preferences. 2. Select the Tools page on the Preferences dialog box. 3. Click Add. 4. Select "Java SDK Commands" from the drop down menu. 5. Click OK. The Java SDK commands are automatically added to the Tools menu, if the Java SDK is installed before TextPad is first run on a PC. 1-12

Programs to use to compile java applications: Eclipse Link to download Eclipse http://www.eclipse.org/ Tutorial: http://web.njit.edu/~soltis/cis114.htm

Exercise 1 What is the problem with the following code fragment: num = 50; while (num >= 0) { System.out.println (num); Num – num + 1; }

Answer 1: This is an infinite loop. The loop will never terminate because the condition will always be true. © 2004 Pearson Addison-Wesley. All rights reserved

Exercise 2: Using a for loop, write a program that displays that squares of all integers greater than 0 and less than or equal to a given number n. © 2004 Pearson Addison-Wesley. All rights reserved

Answer 2: public class ex3 { public static void main (String[] args) int n = 5; int square = 1; for (int i = 1; i <=n; i++) square = i * i; System.out.println(square); } © 2004 Pearson Addison-Wesley. All rights reserved

Exercise 3: Which of the following is a legal Java identifier? 1ForAll oneForAll one/4/all 1_4_all 1forall © 2004 Pearson Addison-Wesley. All rights reserved

Answer 3: b. Explanation: Java identifiers cannot start with a number (so the answers in a, d and e are illegal) and cannot include the “/” character, so the answer in c is illegal. © 2004 Pearson Addison-Wesley. All rights reserved

Exercise 4: Show the output that would occur from the following code, including proper spacing. for (j = 0; j < 5; j++) { for (k = 0; k < 5; k++) if (j!=k) System.out.print(' '); else System.out.print('*'); System.out.println( ); }  

Answer: * © 2004 Pearson Addison-Wesley. All rights reserved

Explanation: The outer loop iterates from 0 to 4, and for each iteration, the inner loop also iterates from 0 to 4. For iteration of the inner loop, if j and k are not the same, a blank is output, otherwise an *. So, if j = 0 and k = 2, then two blanks are output before an *, followed by two more blanks. At the end of each iteration of the inner loop, the cursor is returned to start a new line.