Question

Using Java. The following is a constructor I need to implement but I am not sure how. It also must pass the Junit test. Please give reasoning while answering.

public class LZWDictionary {

// FIELDS

// map (for ease of checking existence of entries)

// list (ease of recall of an entry)

LinkedHashMap<String, Integer> map;

List<String> list;

/**

* Initializes the LZWDictionary to have an initial set of entries taken from

* the set of unique characters in a provided string

*

*

*

* Unique characters are added to a map as they are encountered in the provided

* input string, with an increasing index value (beginning at index 0). At the same

* time, the characters are added to a list. The indices associated with each

* dictionary entry in the map thus relate to their index (position) in the list

*

*

*

*

* @param characters a string of initial characters that may include duplicates

*

* @throws an IllegalArgumentException if the characters string is empty

*

*/

public LZWDictionary(String characters) {

// NOTE: Complete the accessors getMap() and getList() first before running

// your tester on this ctor

}

Must pass this Junit Test

Answer 1

import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;

public class LZWDictionary {

   // FIELDS

   // map (for ease of checking existence of entries)

   // list (ease of recall of an entry)

   LinkedHashMap<String, Integer> map;

   List<String> list;

   /**
   *
   * Initializes the LZWDictionary to have an initial set of entries taken from
   *
   * the set of unique characters in a provided string
   *
   *
   *
   *
   *
   *
   *
   * Unique characters are added to a map as they are encountered in the provided
   *
   * input string, with an increasing index value (beginning at index 0). At the
   * same
   *
   * time, the characters are added to a list. The indices associated with each
   *
   * dictionary entry in the map thus relate to their index (position) in the list
   *
   *
   *
   *
   *
   *
   *
   *
   *
   * @param characters a string of initial characters that may include duplicates
   *
   *
   *
   * @throws an IllegalArgumentException if the characters string is empty
   *
   *
   *
   */

   public LZWDictionary(String characters) {

       // NOTE: Complete the accessors getMap() and getList() first before running

       // your tester on this ctor

       //Initialising map
       map = new LinkedHashMap<>();
       //Initialising list
       list = new ArrayList<>();
       //Declaring String variable for holding character
       String str;
       //Declaring index variable for holding Value
       int index;

       //If block for checking empty string.
       if (characters.length() == 0)
           //Throwing IllegealArgumentException if String is empty.
           throw new IllegalArgumentException("Input should not be empty!!!");
       else {

           //Iterating over the String
           for (int i = 0; i < characters.length(); i++) {
               //Taking particular character in the Iteration
               str = "" + characters.charAt(i);
               //Checking value of a particular character in the map
               if(map.get(str)==null) {
                  
                   //If not present in map, then add that to the map and list
                   map.put(str, 1);
                   list.add(str);
               }
              
               else {
                  
                   index = map.get(str);
                   map.replace(str, index+1);
               }
              
           }
       }

   }

   public LinkedHashMap<String, Integer> getMap() {
       return map;
   }

   public List<String> getList() {
       return list;
   }

}