Question

I am trying to load a file into a Map with a method as below:

private static Map<String,Integer> indexVocabulary;
public static Map<String,Integer> getVocabularyFromFile() throws IOException
{
    FileInputStream fstream = new FileInputStream(VOCABULARY_FILE);
    DataInputStream in = new DataInputStream(fstream);
    BufferedReader br = new BufferedReader(new InputStreamReader(in));      
    String line;
    while( (line = br.readLine()) != null )
    {
        LOG.debug(line);
        String[] kv = line.split(" ");
        LOG.debug(kv[0]);
        LOG.debug(Integer.toString(Integer.parseInt(kv[1])));


        indexVocabulary.put(kv[0], Integer.parseInt(kv[1]));
    }
    return indexVocabulary;
}

I can see output from line‘also from kv[0],kv[1] and Integer.parseInt(kv[1]) However I get a NullPointerException on the line indexVocabulary.put(kv[0], Integer.parseInt(kv[1])); Does anyone know what is wrong with this method?

Answer 1

You don’t initialize indexVocabulary, so it’s null.

Change

private static Map<String,Integer> indexVocabulary;

to

private static Map<String,Integer> indexVocabulary = new HashMap<String,Integer>();