How to do it...

Let's go through the following steps:

1. Open a command-line window. We used the Window's cmd program in this example
2. Set up a path for the OpenNLP tool's bin directory and then navigate to the directory containing the en-lemmatizer.dict file.
3. Execute the following command:

opennlp LemmatizerTrainerME -model en-lemmatizer.bin -lang en -data en-lemmatizer.dict -encoding UTF-8

You will get the following output. It has been shortened here to save space:

Indexing events with TwoPass using cutoff of 5
        Computing event counts...  done. 301403 events        Indexing...  done.

Sorting and merging events... done. Reduced 301403 events to 297777.
Done indexing in 9.09 s.

Incorporating indexed data for training...
done.
   Number of Event Tokens: 297777
   Number of Outcomes: 432
   Number of Predicates: 69122
...done.

Computing model parameters ...
Performing 100 iterations.
  1:  ... loglikelihood=-1829041.6775780176     3.317817009120679E-6
  2:  ... loglikelihood=-452333.43760414346     0.876829361353404
  3:  ... loglikelihood=-211099.05280473927     0.9506806501594212
  4:  ... loglikelihood=-132195.3981804198      0.9667554735686108
...
 98:  ... loglikelihood=-6702.5821153954375     0.9988420818638168
 99:  ... loglikelihood=-6652.6134177562335     0.998845399680826
100:  ... loglikelihood=-6603.518040975329      0.9988553531318534

Writing lemmatizer model
... done (1.274s)
Wrote lemmatizer model to
path: C:\Downloads\OpenNLP\en-lemmatizer.bin

Execution time: 275.369 seconds