incompatible types: Object cannot be converted to CoreLabel

Question

I'm trying to use the Stanford tokenizer with the following example from their website:

import java.io.FileReader;
import java.io.IOException;
import java.util.List;

import edu.stanford.nlp.ling.CoreLabel;
import edu.stanford.nlp.ling.HasWord;
import edu.stanford.nlp.process.CoreLabelTokenFactory;
import edu.stanford.nlp.process.DocumentPreprocessor;
import edu.stanford.nlp.process.PTBTokenizer;

public class TokenizerDemo {

  public static void main(String[] args) throws IOException {
    for (String arg : args) {
      // option #1: By sentence.
      DocumentPreprocessor dp = new DocumentPreprocessor(arg);
      for (List sentence : dp) {
        System.out.println(sentence);
      }
      // option #2: By token
      PTBTokenizer ptbt = new PTBTokenizer(new FileReader(arg),
              new CoreLabelTokenFactory(), "");
      for (CoreLabel label; ptbt.hasNext(); ) {
        label = ptbt.next();
        System.out.println(label);
      }
    }
  }
}

and I get the following error when I try to compile it:

TokenizerDemo.java:24: error: incompatible types: Object cannot be converted to CoreLabel
        label = ptbt.next();

Does anyone know what the reason might be? In case you are interested, I'm using Java 1.8 and made sure that CLASSPATH contains the jar file.

Answer 1

Try parameterizing the PTBTokenizer class. For example:

PTBTokenizer<CoreLabel> ptbt = new PTBTokenizer<>(new FileReader(arg),
          new CoreLabelTokenFactory(), "");