Lab 1: Java Basics, Heap Sort and Eclipse Solution

Objectives




Getting familiar with the Eclipse environment




Creating a Java project; creating and editing a Java program Adding a library to the build path




Running project inside and outside Eclipse







Source files




components.jar HeapSort.java







1 Introduction




Welcome to the first lab. These labs are generally intended to let you explore concepts introduced in the course lectures. During each lab, you need to follow the instructions from problem setup to deliverables. This lab contains 3 deliverables, which you should demo to the lab instructor.




1.1 Eclipse




The Eclipse platform is a generic integrated development environment (IDE) foundation without any focus on a specific programming language. The platform contains IDE functionality and is built with components creating applications by using component subsets. Developers create, share and edit generic projects and files in the platform, while participating within a multiple team development environment repository.




However, it is written mostly in Java and most of the time is used to develop applications in this programming language, but it covers other languages such as: C, C++, Ruby, R, JavaScript, PHP, Python ...




In this lab we will focus on Eclipse usage in writing, editing and running Java programs.







1.2 Java Requirements of Eclipse




Eclipse requires an installed Java runtime (at least Java 5). Java can be downloaded in two flavors, a JRE (Java runtime environment) and a JDK (Java development tools) version. The Eclipse IDE contains its own Java compiler hence a JRE is sufficient for most tasks with Eclipse. The JDK version of Java is required if you compile Java source code on the command line and for advanced development scenarios, for example if you use automatic builds or if you develop Java web applications.

public static void main




1.3 Eclipse Resources

Resource
URL




Eclipse Homepage
http://www.eclipse.org/
Download Eclipse
http://www.eclipse.org/downloads/
Eclipse Online Tutorials
http://www.eclipse.org/resources/









2 Deliverable 1 -- Create and Run a Simple Java Program (Heap Sort)




Sort a list of integers using the heap sort algorithm:




http://www.youtube.com/watch?v=WYII2Oau_VY (Super short, no words, pictures only)




http://www.youtube.com/watch?v=B7hVxCmfPtM (The traditional version from M.I.T., very, very long) Or find your own




Note: Write carefully, you are going to reuse this code later!




Step 1: Launch Eclipse




Open the Eclipse IDE. It can be done at terminal by typing eclipse . Step 2: Create a new project




Select File = New = Java Project = Name your project = Finish. Step 3: Add a new class




Select your project = File = New ⇒ Class = Name the class = check (String[] args) = Finish.







For this lab, just copy the source file HeapSort.java and paste into the src folder of the project. Step 4: Implement your class




Finish the sort method.




Step 5: Run you code




Run the code (Run as = Java application).




DEMO this deliverable to the lab instructor.
























































































3 Deliverable 2 -- Add a Library to the Build Path




In this part, we want you to edit your source code and add a library to the build path.







3.1 Edit Your Code




An import statement is a way of making more of the functionality of Java available to your program. Java can do a lot of things, but you do not need all of them so often. It has its classes divided into packages. Your own classes are part of packages, too. So, anything that isn't in the java.lang package or the local package needs to be imported.







Step 1: Import libraries




Add the two following imports to the beginning of your source code:







import components.simplewriter.SimpleWriter;




import components.simplewriter.SimpleWriter1L;




Step 2: Rewrite the output code







Edit your print / println commands by instantiating an object of SimpleWriter . For example, substitute:







System.out.println(array[c]);




with:







SimpleWriter out = new SimpleWriter1L();

out.println(array[c]);

out.close();

Step 3: Run your code




Run your code and see there are some errors.







The reason for these errors is that the components in the import lines, SimpleWriter and SimpleWriter1L , are from the components.jar, but we have not told Eclipse to use it yet.




3.2 Add the Library to Your Project Build Path




Step 1: Download the library




Save the components.jar in your home directory (or home directory of your project).




Step 2: Configure the project




Right-click on your project = Build Path = Configure Build Path = Add External Jars= Select the library = Finish.




Errors should disappear and you would be able to run your code.




DEMO this deliverable to the lab instructor.







4 Deliverable 3 -- Run Your Java Code outside of Eclipse




Eclipse has implemented its own java compiler called Eclipse Compiler for Java (ECJ), which is based on IBM's Jikes java compiler. Thus, Eclipse is automatically compiling your code on-the-fly to create an instant view of the result. In this part, you need do thing manually.




4.1 Runable JAR




A runnable JAR is just like a EXE file in Windows, which means you can double click it to run. However, what your heap sort is doning is just outputting results into the console, so you still need the terminal/cmd/PowerShell to run it.

Select File = Export... = Java = Runnable JAR file ⇒ Next:




Launch configuration: select your HeapSort;




Export destination: type your target JAR file path and name;




Library handling: choose the last option Copy required libraries into a sub-folder next to the generated JAR.




Click Finish, and you are ready to go:







java −jar HeapSort.jar







4.2 Compile and Run by JDK




Step 1: Copy your source codes to home directory







cp src/HeapSort.java ~ # "~" refers to the home directory of your account cp components.jar ~
Note: your HeapSort.java must use the SimpleWriter and SimpleWriter1L .

































































































Step 2: Configure the CLASSPATH







JDK requires an important environmental variable CLASSPATH to compile and run codes. In Linux, you can do it as follows:

export CLASSPATH="your_class_paths"
#
You need fill in
the actual paths
echo $CLASSPATH
#
Print your class
paths











In this lab, your have two groups of classes:




Your own classes, which in this case is your HeapSort ;




The third party library classes, which is the components.jar.




The CLASSPATH must contain the paths of both groups. Try figure it out.







Step 3: Compile and run




javac HeapSort.java
#
Now you can find the file HeapSort.class at your home directory
java HeapSort
#
Do not add the ".class" extension









DEMO this deliverable to the lab instructor.