CODEWITHSUNDEEP
javaandroidnulltreemap
user1173527
user1173527

Reputation: 21

TreeMap returns null value in field that was just changed

I'm trying to count the frequency of words in a TreeMap. I'm reading a file and passing the lines to a StringTokenizer and converting it afterwards to a string word by word (currentword).

If currentword = "one" then it puts it on the map, but if the second word is one again instead of fetching frequency = 1 it gets null again!

final StringTokenizer parser = new StringTokenizer(currentLine, " \0\t\n\r\f.,;:!?'"); 

while (parser.hasMoreTokens()) { 

        String currentWord = parser.nextToken();

        Integer frequency = frequencyMap.get(currentWord); 

        if (frequency == null) { 
            frequency = 0; 
        } 
        frequency++;
        frequencyMap.put(currentWord, frequency);
    }

Upvotes: 2

Views: 239

Answers (1)

Jon Skeet
Jon Skeet

Reputation: 1500485

Looks like it works fine to me:

import java.util.*;

public class Test
{
    public static void main(String[] args) {
        Map<String, Integer> map = new TreeMap<String, Integer>();
        String[] words = { "x", "one", "y", "one" };

        for (String word : words) {
            Integer frequency = map.get(word);
            if (frequency == null) {
                frequency = 0;
            }
            frequency++;
            map.put(word, frequency);
        }

        System.out.println(map);
    }
}

Output:

{one=2, x=1, y=1}

See if you can come up with a similar short but complete program which demonstrates your problem - possibly by gradually cutting down your "real" code to something similar.

Upvotes: 3

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