Question

java programming

You will be given two interfaces and two abstract classes, FileTextReader, FileTextWriter, AbstractFileMonitor, and AbstractDictionary. Your job is to create two classes the first class should be named FileManager, the second class should be named Dictionary. The FileManager will implement the interfaces FileTextReader and FileTextWriter and extend the clas AbstractFileMonitor. Your class signature would look something like the following:

public class FileManager extends AbstractFileMonitor implements FileTextReader, FileTextWriter{...

The constructor signature of the FileManager should look like the following:

public FileManager(String filePath){...

The Dictionary will extend the abstract class AbstractDictionary. Your class signature would look something like the following:

public class Dictionary extends AbstractDictionary {...

The constructor signature of the Dictionary should look like the following:

public Dictionary(String path, FileManager fileManager) throws IOException {...

Please read the programmatic documentation of the two interfaces and abstract classes to gain an understanding of what each function should do. This assignment will test your knowledge of reading and writing to a text file, implementing interfaces, extending abstract classes, throwing exceptions and working with collections specifically sets.

This project is accompanied by two test classes, ManagerTest, and DictionaryTest. They will test the functionality of the functions in the interfaces and the abstract methods of classes. Its recommended that you implement the FileManager before working on the AbstractDictionary.

Abstract Dictionary

package homework;

import java.io.IOException;
import java.util.Objects;
import java.util.Set;

* A class that holds a collection of words read from a text file. The collection of words is used in the methods of this class
* methods provided in this class.

public abstract class AbstractDictionary {
  
   private final FileTextReader FILE_READER;
   private final Set ALL_WORDS;
  
   /**
   * Creates an abstract dictionary of words using the text file at the specified path.
   * @param path a path to a text file containing a dictionary of words
   * @param dictionaryFileReader the FileReader used to read from the text file at the specified path
   * @throws IOException thrown if there is a problem reading the file at the path
   */
  

public AbstractDictionary(String path, FileTextReader dictionaryFileReader) throws IOException {
       Objects.requireNonNull(dictionaryFileReader, "The File reader can not be null");
       Objects.requireNonNull(path, "The path can not be null");

      FILE_READER = dictionaryFileReader;

       ALL_WORDS = FILE_READER.getAllLines(path);
   }
  
   /**
   * Returns a set of all the words contained in the dictionary text file.
   * @return a set containing all the words in the dictionary file.
   */
  

public Set getAllWords(){
       return ALL_WORDS;
   }
   /**
   * Counts the number of words in this Dictionary that start with the specified prefix and have a length that is equal or greater
   * than the specified size. If size the specified size is less than 1 then word size is not taken into account.
   * @param prefix the prefix to be found
   * @param size the length that the word must equal or be greater than. If a value less than 1 is specified, all words regardless of their
   * characters size should be considered. In other words if the size parameter is < 1 word size is disregarded in the calculations.
   * @param ignoreCase if true this will ignore case differences when matching the strings. If false this considers
   * case differences when matching the strings
   * @return The number of words that start with the specified prefix
   * @throws IllegalArgumentException if the specified string is null or empty (Meaning contains no characters or only white space or blank)
   */

public abstract int countWordsThatStartWith(String prefix, int size, boolean ignoreCase) throws IllegalArgumentException;

   /**
   * Tests if this Dictionary contains at least one word with a length equal to or greater than the specified size that starts with the specified prefix.
   * If size the specified size is less than 1 then word size is not taken into account.
   * @param prefix the prefix to be found
   * @param size the length that the word must equal or be greater than. If a value less than 1 is specified, all words regardless of their
   * characters size should be considered. In other words if the size parameter is < 1 word size is disregarded in the calculations.
   * @param ignoreCase if true this will ignore case differences when matching the strings. If false this considers
   * case differences when matching the strings
   * @return The number of words that start with the specified prefix
   * @throws IllegalArgumentException if the specified string is null or empty (Meaning contains no characters or only white space)
   */
  

public abstract boolean containsWordsThatStartWith(String prefix, int size, boolean ignoreCase) throws IllegalArgumentException;
   * Returns a set of all the words within in this Dictionary that start with the specified prefix and have a length that is equal or greater
   * than the specified size. If size the specified size is less than 1 then word size is not taken into account.
   * @param prefix the prefix to be found
   * @param size the length that the word must equal or be greater than. If a value less than 1 is specified, all words regardless of their
   * characters size should be considered. In other words if the size parameter is < 1 word size is disregarded in the calculations.
   * @param ignoreCase if true this will ignore case differences when matching the strings. If false this considers
   * case differences when matching the strings
   * @return A list of all strings that start with the specified prefix
   * @throws IllegalArgumentException if the specified string is null or empty (Meaning contains no characters or only white space)

   public abstract Set getWordsThatStartWith(String prefix, int size, boolean ignoreCase) throws IllegalArgumentException;
}

AbstractFileMonitor

package homework;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
* A class with methods to monitor a text file.

public abstract class AbstractFileMonitor {

   private MessageDigest messageDigest;
   private int currentCheckSum;
   private boolean hasChanged = false;
   private long nextUpateTime = 0;
  
   public AbstractFileMonitor(String path){
setFilePath(path);
}
   * Updates the variables that correspond to the file being monitored
   * This function has been throttled such that it will only update values every 250 ms. In other words successive calls to this
   * function in time intervals that are less than 250 ms will yield no change.
   * @throws IOException Thrown if any type of I/O exception occurs while writing to the file
   * @throws IllegalStateException If the {@link #setFile(String)} method in not invoked with a proper file prior to invocation of this
   * @throws NoSuchAlgorithmException If the computer's OS is missing the SHA-256 hashing algorithm
   * method. In other words if no file is currently set to be monitored.

   public void update() throws IOException, IllegalStateException, NoSuchAlgorithmException {

      if(messageDigest == null){
           messageDigest = MessageDigest.getInstance("SHA-256");
       }
      
       if(nextUpateTime > System.currentTimeMillis()) {
           hasChanged = false;
          
          return;
       }
      
      nextUpateTime = System.currentTimeMillis() + 250;
      
       File file = new File(getFilePath());
      
       if(!file.exists()) return;
      
try (DigestInputStream dis = new DigestInputStream(new FileInputStream(getFilePath()), messageDigest)) {
while (dis.read() != -1) ;
messageDigest = dis.getMessageDigest();
}

StringBuilder result = new StringBuilder();
for (byte b : messageDigest.digest()) {
result.append(String.format("%02x", b));
}
  
hasChanged = currentCheckSum != result.toString().hashCode();
  
currentCheckSum = result.toString().hashCode();
   }
   * Tests if the file being monitored has changed since the last time {@link #update()} was invoked
   public boolean hasChanged(){
       return hasChanged;
}
   public abstract void setFilePath(String path);
   public abstract String getFilePath() throws IllegalStateException;
}

FileTextReader

package homework;

import java.io.IOException;
import java.util.Collection;
import java.util.List;
import java.util.Set;

public interface FileTextReader{
   public String readText(String path) throws IOException;
   * @throws IOException Thrown if any type of I/O exception occurs while writing to the file

public Set getAllLines(String path) throws IOException;
   * @throws IOException Thrown if any type of I/O exception occurs while writing to the file
public String getLastLine(String path) throws IOException;
}

FileTextWriter

package homework;

import java.io.IOException;

public interface FileTextWriter {
   * @throws IOException Thrown if any type of I/O exception occurs while writing to the file
   * @throws IllegalArgumentException if the specified string is null or empty (Meaning contains no characters or only white space)
   public void writeToFile(String string, String path) throws IOException, IllegalArgumentException;
}

Answer 1

Java code for FileManager class and Dictionary class and test classes for both are given below.

FileManager class

package filedemo;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.HashSet;
import java.util.Set;

public class FileManager extends AbstractFileMonitor implements FileTextReader, FileTextWriter{
    String filePath;
    public FileManager(String filePath){
        super(filePath);
        this.filePath=filePath;
    }

    @Override
    public void setFilePath(String path) {
        filePath=path;
    }

    @Override
    public String getFilePath() throws IllegalStateException {
        return filePath;
    }

    @Override
    public String readText(String path) throws IOException {
        String ot="";
        File file = new File(path); 
        BufferedReader br = new BufferedReader(new FileReader(file));  
        String st;
        while ((st = br.readLine()) != null) {
        ot+=st+"\n"; 
        } 
        return ot;
    }

    @Override
    public Set getAllLines(String path) throws IOException {
        Set<String> set = new HashSet<String>();
        File file = new File(path); 
        BufferedReader br = new BufferedReader(new FileReader(file));  
        String st;
        while ((st = br.readLine()) != null) {
        set.add(st);
        } 
        
        return set;
    }

    @Override
    public String getLastLine(String path) throws IOException {
        String st="";
        String ot="";
        File file = new File(path); 
        BufferedReader br = new BufferedReader(new FileReader(file));  
        while ((st = br.readLine()) != null) {
           ot=st;
        }
        return ot;
    }

    @Override
    public void writeToFile(String string, String path) throws IOException, IllegalArgumentException {
       File myObj = new File(path);
       if(myObj==null)
       {
           myObj.createNewFile();
       }
       else
       {
            FileWriter myWriter = new FileWriter(path);
            myWriter.write(string);
            myWriter.close();
       }
    }
}
    

ManagerTest class

/*
 * To test FileManager
 */
package filedemo;

import java.io.IOException;

public class ManagerTest {
    
    public void Test()throws IOException
    {
     String filename="E:\\Words.txt";
     String filenamew="E:\\Wordsw.txt";
     FileManager obj=new FileManager(filename);
     System.out.println("Read Text");
     System.out.println(obj.readText(filename));
     System.out.println("All Lines using set");
     System.out.println(obj.getAllLines(filename));
     System.out.println("Last line in file");
     System.out.println(obj.getLastLine(filename));
     obj.writeToFile("HaiWr", filenamew);
    }   
    
}

input

content in Words.txt

output

Dictionary Class

package filedemo;

import java.io.IOException;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class Dictionary extends AbstractDictionary{
    Set<String> set = new HashSet<String>();
    public Dictionary(String path, FileManager fileManager) throws IOException {
        super(path,fileManager);
        set=getAllWords();
    
    }

    @Override
    public int countWordsThatStartWith(String prefix, int size, boolean ignoreCase) throws IllegalArgumentException {
        int count=0;     
        String st;       
        for(Iterator<String> it = set.iterator(); it.hasNext();) {
            st=it.next();
            if(ignoreCase)
            {
               prefix=prefix.toUpperCase();
               st=st.toUpperCase();               
            }
            if(st.startsWith(prefix) && st.length()>=size)
            {
                count++;
            }
         }        
        return count;
    }

    @Override
    public boolean containsWordsThatStartWith(String prefix, int size, boolean ignoreCase) throws IllegalArgumentException {
       
        boolean result=false;
        int count=0;
      
        String st;
        
        for(Iterator<String> it = set.iterator(); it.hasNext();) {
            st=it.next();
            if(ignoreCase)
            {
               prefix=prefix.toUpperCase();
               st=st.toUpperCase();               
            }
            if(st.startsWith(prefix) && st.length()>=size)
            {
                count++;
            }
         }
        if(count==0)
        {
            result=false;
        }else
        {
            result=true;
        }
        return result;
    }

    @Override
    public Set getWordsThatStartWith(String prefix, int size, boolean ignoreCase) throws IllegalArgumentException {
        Set<String> seto = new HashSet<String>();
         String st;       
        for(Iterator<String> it = set.iterator(); it.hasNext();) {
            st=it.next();
            if(ignoreCase)
            {
               prefix=prefix.toUpperCase();
               st=st.toUpperCase();               
            }
            if(st.startsWith(prefix) && st.length()>=size)
            {
                seto.add(st);
            }
         }        
        return seto;
    }
    
    
}

DictionaryTest class

/*
 * To test dictionary.
 
 */
package filedemo;

import java.io.IOException;

public class DictionaryTest {
    public void run() throws IOException    
    {
         String filename="E:\\Words.txt";       
        FileManager objf=new FileManager(filename);
        Dictionary obj=new Dictionary(filename,objf);
        System.out.println("Count of words start with He not ignore case");
        System.out.println(obj.countWordsThatStartWith("He", 0, false));
        System.out.println("exist or not words start with He ignore case");
        System.out.println(obj.containsWordsThatStartWith("He", 0, true));
        System.out.println("set of words start with He not ignore case");
        System.out.println(obj.getWordsThatStartWith("He", 0, false));
    }
    
}

Driver program

package filedemo;

import java.io.IOException;

public class FileDemo {

    public static void main(String[] args)throws IOException {
        ManagerTest obj=new ManagerTest();
        obj.Test();
        DictionaryTest dobj=new DictionaryTest();
        dobj.run();
    }
    
}

*please change the package name.

package filedemo; to your package name.

output