Question

Can someone please add clear and concise comments thoroughly explaining each line of code below. Just need help understanding the code, don't need to modify it.

The purpose of the code is to count the frequency of words in a text file, and return the most frequent word with its count. It uses two algorithms:

Algorithm 1 is based on the data structure LinkedList. It maintains a list for word frequencies. The algorithm runs by scanning every token in the input stream, and increments its corresponding frequency count.

Algorithm 2 uses two arrays to keep track of the counts.

Code:

import java.io.File;
import java.util.Scanner;
import java.util.Map.Entry;
import java.util.AbstractMap;
import java.util.LinkedList;

public class WordCountLinkedList254{

    public static Entry count_ARRAY(String[] tokens) {

        int CAPACITY = 10000;
        String[] words = new String[CAPACITY];
        int[] counts = new int[CAPACITY];

        for (int j = 0; j < tokens.length; j++) {
            String token = tokens[j];
            for (int i = 0; i < CAPACITY; i++) {
                if (words[i] == null) {
                    words[i] = token;
                    counts[i] = 1;
                    break;
                } else if (words[i].equals(token))
                    counts[i] = counts[i] + 1;
            }
        }
        int maxCount = 0;
        String maxWord = "";
        for (int i = 0; i < CAPACITY & words[i] != null; i++) {
            if (counts[i] > maxCount) {
                maxWord = words[i];
                maxCount = counts[i];
            }
        }
        return new AbstractMap.SimpleEntry < String, Integer > (maxWord, maxCount);
    }
  
   public static Entry count_LINKED_LIST(String[] tokens) {
        LinkedList> list = new LinkedList> ();
        for (int j = 0; j < tokens.length; j++) {
            String word = tokens[j];
            boolean found = false;

            /* for (int i = 0; i < list.size(); i++) {
            Entry e = list.get(i);
            if (word.equals(e.getKey())) {
            e.setValue(e.getValue() + 1);
            list.set(i, e);
            found = true;
            break;
               }
            }*/

            int i = 0;
            for (Entry e: list) {
                if (word.equals(e.getKey())) {
                    e.setValue(e.getValue() + 1);
                    list.set(i, e);
                    i++;
                    found = true;
                    break;
                }
            }

            if (!found)
                list.add(new AbstractMap.SimpleEntry (word, 1));
        }
        int maxCount = 0;
        String maxWord = "";
        for (int i = 0; i < list.size(); i++) {
            int count = list.get(i).getValue();
            if (count > maxCount) {
                maxWord = list.get(i).getKey();
                maxCount = count;
            }
        }
        return new AbstractMap.SimpleEntry < String, Integer > (maxWord, maxCount);
    }
  
    static String[] readText(String PATH) throws Exception {
        Scanner doc = new Scanner(new File(PATH)).useDelimiter("[^a-zA-Z]+");
        int length = 0;
        while (doc.hasNext()) {
            doc.next();
            length++;
        }
      
        String[] tokens = new String[length];
        Scanner s = new Scanner(new File(PATH)).useDelimiter("[^a-zA-Z]+");
        length = 0;
        while (s.hasNext()) {
            tokens[length] = s.next().toLowerCase();
            length++;
        }
        doc.close();
      
        return tokens;
    }
  
    public static void main(String[] args) throws Exception {
      
        String PATH = "/Users/jianguolu/Dropbox/254/code/dblp1k.txt ";
        String[] tokens = readText(PATH);
        long startTime = System.currentTimeMillis();
        Entry entry = count_LINKED_LIST(tokens);
        long endTime = System.currentTimeMillis();
        String time = String.format("%12d", endTime - startTime);
        System.out.println("time\t" + time + "\t" + entry.getKey() + ":" + entry.getValue());
      
        tokens = readText(PATH);
        startTime = System.currentTimeMillis();
        entry = count_ARRAY(tokens);
        endTime = System.currentTimeMillis();
        time = String.format("%12d", endTime - startTime);
        System.out.println("time\t" + time + "\t" + entry.getKey() + ":" + entry.getValue());
    }
}

Answer 1

import java.io.File;
import java.util.Scanner;
import java.util.Map.Entry;
import java.util.AbstractMap;
import java.util.LinkedList;

public class WordCountLinkedList254{

public static Entry count_ARRAY(String[] tokens) {

int CAPACITY = 10000;
// here declaring array to store the 10000 words
String[] words = new String[CAPACITY];
//another integer array to maintain the count of words
int[] counts = new int[CAPACITY];

// iterating the words in the array
// by taking each word
for (int j = 0; j < tokens.length; j++) {
   // pulling out word into token
String token = tokens[j];
// starting from the 0 so compare the selected word with every word in the words list
// so that we will get the count
for (int i = 0; i < CAPACITY; i++) {
   // if words[i] is null than it is first time
   //adding count as 1
if (words[i] == null) {
words[i] = token;
counts[i] = 1;
break;
  
}// if already exist same token increase count at i +1
else if (words[i].equals(token))
counts[i] = counts[i] + 1;
}
}
int maxCount = 0;
String maxWord = "";
// iterating the counts array to find the word which occurs more number of times
for (int i = 0; i < CAPACITY & words[i] != null; i++) {
if (counts[i] > maxCount) {
maxWord = words[i];
maxCount = counts[i];
}
}
// returning the word and its count
return new AbstractMap.SimpleEntry < String, Integer > (maxWord, maxCount);
}
  

// this part the program is not correct. it is wrong
public static Entry count_LINKED_LIST(String[] tokens) {
//created linked list to stored the value
   LinkedList list = new LinkedList ();
  
for (int j = 0; j < tokens.length; j++) {
   // pulling the each token
String word = tokens[j];
boolean found = false;

/* for (int i = 0; i < list.size(); i++) {
Entry e = list.get(i);
if (word.equals(e.getKey())) {
e.setValue(e.getValue() + 1);
list.set(i, e);
found = true;
break;
}
}*/

int i = 0;
//iterating the list
// check if value already exist
for (Entry e: list) {
if (word.equals(e.getKey())) {
e.setValue(e.getValue() + 1);
list.set(i, e);
i++;
found = true;
break;
}
}

if (!found)
list.add(new AbstractMap.SimpleEntry (word, 1));
}
int maxCount = 0;
String maxWord = "";
for (int i = 0; i < list.size(); i++) {
int count = list.get(i).getValue();
if (count > maxCount) {
maxWord = list.get(i).getKey();
maxCount = count;
}
}
return new AbstractMap.SimpleEntry < String, Integer > (maxWord, maxCount);
}
  
// this method reads the words from the file and returns array of words
static String[] readText(String PATH) throws Exception {
Scanner doc = new Scanner(new File(PATH)).useDelimiter("[^a-zA-Z]+");
int length = 0;
//finding the number of words in the file
while (doc.hasNext()) {
doc.next();
length++;
}
  
//creating the array with size number of words
String[] tokens = new String[length];
Scanner s = new Scanner(new File(PATH)).useDelimiter("[^a-zA-Z]+");
length = 0;
// splitting each word
while (s.hasNext()) {
   //putting into the array
tokens[length] = s.next().toLowerCase();
length++;
}
doc.close();
  
//returning array
return tokens;
}
  
public static void main(String[] args) throws Exception {
  
   // path where file exist
String PATH = "/Users/jianguolu/Dropbox/254/code/dblp1k.txt ";
//calling method to get the array of words
String[] tokens = readText(PATH);
// noted starting the timer
long startTime = System.currentTimeMillis();
//calling linked list method
Entry entry = count_LINKED_LIST(tokens);
//noting end time
long endTime = System.currentTimeMillis();
//finding total time it took to compute
String time = String.format("%12d", endTime - startTime);
System.out.println("time\t" + time + "\t" + entry.getKey() + ":" + entry.getValue());
  
//reading tokens into another array
tokens = readText(PATH);
//noting starting time
startTime = System.currentTimeMillis();
///caling array functionality
entry = count_ARRAY(tokens);
//noted end time
endTime = System.currentTimeMillis();
//finding time took to complete functionality
time = String.format("%12d", endTime - startTime);
System.out.println("time\t" + time + "\t" + entry.getKey() + ":" + entry.getValue());
}
}

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