Question

Java Question

I have a Queue containing String type taking in a text file with an iterator.

I need to use ArrayList and HashMap for freqHowMany to get a frequency table in descending order by the highest frequency words in the text. Any help would be much appreciated and thanks!

final Iterator input = new Scanner(System.in).useDelimiter("(?U)[^\\p{Alpha}0-9']+");
        final Queue queueFinal = new CircularFifoQueue<>(wordsLast);

        while (input.hasNext()) {
            final String queueWord = input.next();
            if (queueWord.length() > minimumLength) {
                queueFinal.add(queueWord); // the oldest item automatically gets evicted
            }

            System.out.println(queueFinal);
        }
    }
}

EXAMPLE:

Your program prints an updated word cloud for each sufficiently long word read from the standard input.

The program takes up to three positive command-line arguments:

• freqHowMany indicates the size of the word cloud, i.e., the number of words in descending order of frequency to be shown
• wordMinLength indicates the minimum length of a word to be considered; shorter words are ignored
• wordLastNwords indicates the size of a moving window of n most recent words of sufficient length for which to update the word cloud

Your program then reads a continuous stream of words, separated by whitespace or other non-word characters, from the standard input. (A word can have letters, numbers, or single quotes.) For each word read, your program prints to standard output, on a single line, a textual representation of the word cloud of the form

The idea is to connect this tool to a streaming data source, such as Twitter, or speech-to-text from a 24-hour news channel, and be able to tell from the word cloud in real time what the current "hot" topics are.

THANKS!

Answer 1

There are two ways to handle this.

1) Use a TreeMap which is sorted by values. In this way, you would get the words in the descending order of frequency.

Sample code:

import java.util.*;

public class SortMap {
    public static <K, V extends Comparable<V>> Map<K, V>
    sortByValues(final Map<K, V> map) {
        Comparator<K> valueComparator =
                new Comparator<K>() {
                    public int compare(K k1, K k2) {
                        return map.get(k2).compareTo(map.get(k1));
                    }
                };

        Map<K, V> sortedByValues =
                new TreeMap<K, V>(valueComparator);
        sortedByValues.putAll(map);
        return sortedByValues;
    }


public static void main(String[] args) {        

Queue<String> q = new LinkedList<>();
q.add("a");
q.add("b");
q.add("c");
q.add("b");
q.add("b");
q.add("b");
q.add("b");
q.add("c");
q.add("c");
HashMap<String, Integer> map = new HashMap<>();
while (!q.isEmpty()) {
    map.put(q.peek(), map.getOrDefault(q.poll(), 0) + 1);
}

        TreeMap<String, Integer> sortedMap = (TreeMap<String, Integer>) sortByValues(map);
        sortedMap.keySet().stream().forEach(k -> System.out.println(k+"->"+sortedMap.get(k)));
    }
}

Output:

b->5
c->3
a->1


2) Since the frequency of words is what matters, we can transfer the HashMap<String, Integer> to a TreeMap<Integer, String> which sorts the table in descending order of frequency (i.e.) store the key of HashMap as value and value of HashMap as key.
Sample code:

import java.util.*;

public class SortMap {

public static void main(String[] args) {
Queue<String> q = new LinkedList<>();
q.add("a");
q.add("b");
q.add("c");
q.add("b");
q.add("b");
q.add("b");
q.add("b");
q.add("c");
q.add("c");
HashMap<String, Integer> map = new HashMap<>();
while (!q.isEmpty()) {
    map.put(q.peek(), map.getOrDefault(q.poll(), 0) + 1);
}
        TreeMap<Integer, String> sortedMap = new TreeMap<>((v1,v2) -> (v2 - v1));
        map.keySet().stream().forEach(k -> sortedMap.put(map.get(k), k));
        sortedMap.keySet().stream().forEach(k -> System.out.println(k+"->"+sortedMap.get(k)));
    }
}

Output:

b->5
c->3
a->1