George Blank University Lecturer

CS 602 Java and the Web Object Oriented Software Development Using Java Chapter 3

Chapter Overview Chapter 3 is an introduction to the Java language. Java is available in various subsets of the language so that different editions can serve uses ranging from supporting large enterprise application distributed over many systems to small embedded controllers running devices such as a home thermostat and even smart cards. Understand the features of the language, the various editions of Java, the run-time architecture, applications and applets.

Editions for this course This course is based on the Java 2 Standard Edition (J2SE), version 1.7 or later. If you choose to do a project from chapter 12, you may wish to use the Java 2 Enterprise Edition (J2EE) instead. You should be able to give a short explanation of the difference between the various editions of Java.

Run-time Architecture The text has a good, concise basic explanation of the Java run-time architecture (Section 3.2). It is important to understand this material. I have discovered that many employers have been very concerned with security, so study and understand the supplemental lecture on Java Security as well.

Getting Started Most common problems in Java development come from setting up the environment, especially the classpath.

Hello From Venus Code /* * Copyright (c) , Xiaoping Jia. All Rights Reserved. */ import java.awt.*; import java.applet.Applet; public class HelloFromVenus extends Applet { public void paint(Graphics g) { Dimension d = getSize(); g.setColor(Color.black); g.fillRect(0,0,d.width,d.height); g.setFont(new Font("Helvetica", Font.BOLD, 24)); g.setColor(new Color(255, 215, 0)); // gold color g.drawString("Hello From Venus!", 40, 25); g.drawImage(getImage(getCodeBase(), "Venus.gif"), 20, 60, this); }

Programming Problems Be familiar with the common problems and solutions on page 72 of the text. The primary means of technical support in this class will be self help from your classmates in the Technical Support thread on Moodle. You must learn to describe your problem well. You will also be expected to become familiar with the Java Documentation.

Most common problem in Java - Setting Environment You can set the class path for Java from the operating system with set classpath= {your class location} In most Windows systems, you can search Help for “environment variables” to find out how to set your classpath.

Other common problems The command to compile is javac {yourfilename}.java On AFS, you cannot connect to afs.njit.edu. You must specify a specific host between afsaccess1.njit.edu and afsacess4.njit.edu. Typing java – version will tell you what version of Java is currently active on your system. If you have multiple versions installed, you might have problems.

Works on Windows, not UCS If your program works in Windows, but not on Unix or OSX: Programs loaded over a network cannot access files and libraries on the local machine without policy files, signed jars, or security managers. Windows allows spaces in file names. Unix requires them to be filled. (Use %20 in HTML) Unix requires shorter filenames. Unix and Java are case sensitive, Windows ignores case, so MyFile.Class = myfile.class. Windows allows \ in pathnames. Unix requires /. If you neet to run and applet, Appletviewer is less restrictive than browsers.

Some useful links at NJIT This is the main help site: If you use a Virtual Private Network get software and installation instructions here:

Bibliography Be especially familiar with the documentation accessed from the Reference menu on the left side of this page. This is also where you can download Java. Jia, Xiaoping, Object Oriented Software Development Using Java. Addison Wesley, 2003