Finding repeated words on a string and counting the repetitions

Question

I need to find repeated words on a string, and then count how many times they were repeated. So basically, if the input string is this:

String s = "House, House, House, Dog, Dog, Dog, Dog";

I need to create a new string list without repetitions and save somewhere else the amount of repetitions for each word, like such:

New String: "House, Dog"

New Int Array: [3, 4]

Is there a way to do this easily with Java? I've managed to separate the string using s.split() but then how do I count repetitions and eliminate them on the new string? Thanks!

Answer 1

You've got the hard work done. Now you can just use a Map to count the occurrences:

Map<String, Integer> occurrences = new HashMap<String, Integer>();

for ( String word : splitWords ) {
   Integer oldCount = occurrences.get(word);
   if ( oldCount == null ) {
      oldCount = 0;
   }
   occurrences.put(word, oldCount + 1);
}

Using map.get(word) will tell you many times a word occurred. You can construct a new list by iterating through map.keySet():

for ( String word : occurrences.keySet() ) {
  //do something with word
}

Note that the order of what you get out of keySet is arbitrary. If you need the words to be sorted by when they first appear in your input String, you should use a LinkedHashMap instead.

Answer 2

Once you have got the words from the string it is easy. From Java 10 onwards you can try the following code:

import java.util.Arrays;
import java.util.stream.Collectors;

public class StringFrequencyMap {
    public static void main(String... args) {
        String[] wordArray = {"House", "House", "House", "Dog", "Dog", "Dog", "Dog"};
        var freq = Arrays.stream(wordArray)
                         .collect(Collectors.groupingBy(x -> x, Collectors.counting()));
        System.out.println(freq);
    }
}

Output:

{House=3, Dog=4}

Answer 3

Try this,

public class DuplicateWordSearcher {
@SuppressWarnings("unchecked")
public static void main(String[] args) {

    String text = "a r b k c d se f g a d f s s f d s ft gh f ws w f v x s g h d h j j k f sd j e wed a d f";

    List<String> list = Arrays.asList(text.split(" "));

    Set<String> uniqueWords = new HashSet<String>(list);
    for (String word : uniqueWords) {
        System.out.println(word + ": " + Collections.frequency(list, word));
    }
}

}

Answer 4

public class StringsCount{

    public static void main(String args[]) {

        String value = "This is testing Program testing Program";

        String item[] = value.split(" ");

        HashMap<String, Integer> map = new HashMap<>();

        for (String t : item) {
            if (map.containsKey(t)) {
                map.put(t, map.get(t) + 1);

            } else {
                map.put(t, 1);
            }
        }
        Set<String> keys = map.keySet();
        for (String key : keys) {
            System.out.println(key);
            System.out.println(map.get(key));
        }

    }
}

Answer 5

As mentioned by others use String::split(), followed by some map (hashmap or linkedhashmap) and then merge your result. For completeness sake putting the code.

import java.util.*;

public class Genric<E>
{
    public static void main(String[] args) 
    {
        Map<String, Integer> unique = new LinkedHashMap<String, Integer>();
        for (String string : "House, House, House, Dog, Dog, Dog, Dog".split(", ")) {
            if(unique.get(string) == null)
                unique.put(string, 1);
            else
                unique.put(string, unique.get(string) + 1);
        }
        String uniqueString = join(unique.keySet(), ", ");
        List<Integer> value = new ArrayList<Integer>(unique.values());

        System.out.println("Output = " + uniqueString);
        System.out.println("Values = " + value);

    }

    public static String join(Collection<String> s, String delimiter) {
        StringBuffer buffer = new StringBuffer();
        Iterator<String> iter = s.iterator();
        while (iter.hasNext()) {
            buffer.append(iter.next());
            if (iter.hasNext()) {
                buffer.append(delimiter);
            }
        }
        return buffer.toString();
    }
}

New String is Output = House, Dog

Int array (or rather list) Values = [3, 4] (you can use List::toArray) for getting an array.