COMP3021: Java Programming

COMP3021: Java Programming (Spring 2016)

Lab 1(Date 12/02/2016)

Objectives

Java Development Environment Setup

Set up Java in local machine

Try to run Sample Java programs in Environment

Debugging Basics

Learn some simple but efficient tricks for debugging Java programs

Eclipse Tutorial

Get familiar with Eclipse IDE

Java development in Eclipse

Assessment

Try to fix all the bugs in few demo programs

Procedure to set up Environment

Set up Java development environment in local machine

Download and install Java Development Kit (JDK) on your local machine. Helpful video for installation
The bin folder contains all the java tools like compilation (javac), execution (java/javaw), applet viewer (appletviewer) and so on. To use the command javac to compile Java source code, you need to set the system environment variable: PATH and CLASSPATH, so that the system knows where to find the command and the class (libraries).
In Windows 95/98/ME, add the following lines at the end of c:\autoexec.bat

set PATH=C:\Program Files\Java\jdk1.7.0_18\bin;%PATH%
set CLASSPATH=.;C:\Program Files\Java\jdk1.7.0_18\jre\lib;%CLASSPATH%
set JAVA_HOME=C:\Program Files\Java\jdk1.7.0_18

In Windows 2000/XP professional:

Click Control Panel > System > Advanced > Environment Variables.
Double click PATH, CLASSPATH and JAVA_HOME, to edit the values; or click "New..." to add a new variable.

Windows 7:

Select Computer from the Start menu
Choose System Properties from the context menu
Click Advanced system settings > Advanced tab
Click on Environment Variables, under System Variables, find PATH, and click on it.
In the Edit windows, modify PATH by adding the location of the class to the value for PATH. If you do not have the item PATH, you may select to add a new variable and add PATH as the name and the location of the class as the value. Reopen Command prompt window, and run your java code.

Helpful Site to set or change the PATH system variable (Windows)
In Unix, edit ~/.cshrc_user

setenv PATH /usr/local/packages/java/bin:${PATH}
setenv CLASSPATH .:/usr/local/packages/java/jre/lib
setenv JAVA_HOME /usr/local/packages/java
Helpful Site to Set JAVA_HOME / PATH variables Under Linux Bash Profile

Mac OSX 10.5 or later,

$ vim .bash_profile
export JAVA_HOME=$(/usr/libexec/java_home)
$ source .bash_profile
$ echo $JAVA_HOME /Library/Java/JavaVirtualMachines/1.7.0.jdk/Contents/Home
Helpful Site to Set $JAVA_HOME environment variable on Mac OS X

Try two toy Java programs

Download HelloWorld.java Program
Open a command prompt by clicking: start > run > type in " cmd" > OK
To compile HelloWorld.java, type: (.java is needed)

javac HelloWorld.java

To execute it, type: (.class CANNOT be specified)

java HelloWorld

To compile and run StdIOTest.java:

javac StdIOTest.java
java StdIOTest > StdIOTest.html

To end std input, use ctrl+Z in Windows, or ctrl+D in Linux.

Useful Tricks for Debugging

Here we introduce some simple tricks for debugging Java programs. For more sophisticated debugging techniques, refer to Eclipse tutorial
An efficient way for tracking Java programs is to print or log the values of the variables with code like this:

System.out.println("x=" + x);
mylogger.info("x=" + x); after creating a Logger named "mylogger" using Logger mylogger = Logger.getLogger("mylogger");

We can set the level to which the messages will be logged:

mylogger.setLevel(Level.ALL);
mylogger.setLevel(Level.OFF); // turns off the logger

Here is an example, FactorialLog.java, which uses Logger to track the computation of factorials.
Instead of the default Logger, we can use customized loggers for advanced features. An example is given in HelloWorldLog.java.

Eclipse Tutorial

Download the Eclipse tutorial
Follow the steps in the tutorial.
Click here to download Eclipse tutorial

Assessment

Could you try to fix all the bugs in the simple programs using Eclipse?
Click here to download Lab1 Assignments