miro-bezak / pb162-hw03-find

Third graded assigment from the course PB162 Programming in Java

Homework assignment no. 3, Find

Publication date: December 6th

Submission deadline: December 23rd

Changelog

General information

In this assignment you will implement a command line utility used for file search. You can think of it as a simplified version of find or grep utilities known from unix.

Your program will allow its users to search for files and directories using various filters and specify the ordering used to print out the result.

The maximum number of points for this assignment is 11.

• 6.5 points for passing tests (attached tests do not guarantee a 100% correctness).
• 3.5 points for correct implementation (evaluated by your class teacher).
• 1 point for clean and elegant implementation (code conventions, minimal code repetition).

In cases when provided tests do not pass with submitted solution you can be granted no more than 4 points (this means that you can be granted 0 points as well)!

Preconditions

To succesfuly implement this assignment you need to know the following

1. Work with collection.
2. Work with comparators
3. Work with some of the classes from java.nio package
4. Understand more complex code provided by 3rd party.

Project structure

The structure of project provided as a base for your implementation should meet the following criteria.

1. Package cz.muni.fi.pb162.find contains classes and interfaces provided as part of the assignment.

• Do not modify or add any classes or subpackages into this package.

2. Package cz.muni.fi.pb162.find.impl should contain your implementation.

• Anything outside this package will be ignored during evaluation.

Names in this document

Unless fully classified name is provided, all class names are relative to package cz.muni.fi.pb162.find or cz.muni.fi.pb162.find.impl for classes implemented as part of your solution.

Assignment description/documentation

The following is only a high-level description of given assignment. For specifics please consult the detailed javadoc documentation provided for each class and interface.

Compiling the project

The project can be compiled and packaged in the same way you already know.

$ mvn clean compile

The only difference is, that unlike with seminar project, this time checks for missing documentation and style violation will produce an error. You can temporarily disable this behavior when running this command.

$ mvn clean compile -Dcheckstyle.fail=false

You can consult your seminar teacher to help you set the checkstyle.fail property in your IDE (or just google it).

If you wish to run tests from IDE, make sure you set the working directory is set to the root of the project.

Submitting the assignment

The procedure to submit your solution may differ based on your seminar group. However generally it should be ok to submit target/hw03-find-1.0-SNAPSHOT-sources.jar to the homework vault. While working on ths assignment you are free to create any additional classes/interfaces/methods/... as long as they are kept within the cz.muni.fi.pb162.find.impl package

Step 1: Gather directories and files

Before we start doing anything fancy (e.g. applying filters) we actually need a list of entries (files and directories) to work with.

Create a class impl.FSWalkResultImpl extending cz.muni.fi.pb162.find.filesystem.FSWalkResult.

Looking at FSWalkResult you may notice that it extends -- java.nio.file.SimpleFileVisitor<Path>. This class provides the necessary methods for traversing the filesystem, stopping at each file or directory and performing some actions with it.

SimpleFileVisitor is a regular class and as such provides an implementation for all its methods. However this implementation doesn't really do anything except looking at the visited entry and continuing the walk. This means your FSWalkResultImpl will have to override some of these methods. It shouldn't be too hard to determine which. If you are not sure, this task is a great candidate for a discussion with your classmates on course forums.

Yes we know, SimpleFileVisitor was not taught at the lecture and this may seem a bit confusing. However part of what makes a great software engineer is the ability to study and understand documentation and code written by somebody else. Take a deep breath and go through the documentation for these classes. Things should start making sense pretty fast.

Step 2: Implement Filters

In order to narrow the result set to only those files and directories we are interested in, we will implement a number of filters. Filter classes should extend cz.muni.fi.pb162.find.filters.BasicFilter and should be placed inside cz.muni.fi.pb162.find.impl.filters package. All filter classes should also have a constructor accepting the list of entries to be filtered (List<SearchEntry>).

Implement the following filters:

filter class	additional constructor parameter	description	Additional info
FileNameFilter	String regex	filter based on file/directory name.	String#matches(String)
MaxSizeFilter	long maxSize	filter based on maximum size of file/directory
MinSizeFilter	long minSize	filter based on minimum size of file/directory
FileContentFilter	String regex	filter based on the content of a file	String#matches(String) is sufficient

By examining the BasicFilter class, it should be clear that you only need to create a constructor and implement the filter(SearchEntry path) method.

Step 3: Implement Comparators

The last bit of functionality we want to add to our application is the ability to sort the result of our search. This means implementing a bunch of comparators. Comparator classes should implement cz.muni.fi.pb162.find.comparators.BasicComparator and should be placed inside cz.muni.fi.pb162.find.impl.comparators package. All comparator classes (except FilePathComparator) should also have a constructor accepting the next comparator (BasicComparator). The next comparator is used if compared entries are equal.

Implement the following comparators:

comparator class	description
FilePathComparator	Compare entries based on their absolute path
FileNameComparator	Compare entries based on their name.
FileExtensionComparator	Compare entries based on their extension (files only)
FileSizeComparator	Compare entries based on their size

The reason why FilePathComparator doesn't accept a next comparator is that there can't be two entries with the same absolute path on the filesystem. Step 4: Implement Actions

Create an implementations of cz.muni.fi.pb162.find.actions.FilterAction interface in impl.actions.FilterActionImpl. This class represents a main execution point for filtering the result of the walk over filesystem we have done earlier.

Create an implementations of cz.muni.fi.pb162.find.actions.SortAction interface in impl.actions.SortActionImpl. This class represents a main execution point for ordering the filtered results.

More information can be obtained by reading provided javadoc for these classes. Also have a look at how are these used in the code provided as part of the assignment.

Running the program

Once you are done with your implementation you can build the program by executing

mvn clean install

This will build an executable jar file inside target directory. The following command will print the basic usage help.

java -jar find-1.0-SNAPSHOT.jar --help