Let's go through the following steps:

1. Add the following imports to the project:

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import opennlp.tools.lemmatizer.LemmatizerME;
import opennlp.tools.lemmatizer.LemmatizerModel;

2. Add the following try block to the main method. An input stream and model are created, followed by the instantiation of the lemmatization model:

LemmatizerModel lemmatizerModel = null;
try (InputStream modelInputStream = new FileInputStream(
        "C:\Downloads\OpenNLP\en-lemmatizer.bin")) {
    lemmatizerModel = new LemmatizerModel(modelInputStream);
    LemmatizerME lemmatizer = new LemmatizerME(lemmatizerModel);
    …
} catch (FileNotFoundException e) {
    // Handle exception
} catch (IOException e) {
    // Handle exception
}

3. Add the following code to the end of the try block. It sets up arrays holding the words of the sample text and their POS tags. It then performs the lemmatization and displays the results:

String[] tokens = new String[] { 
    "The", "girls", "were", "leaving", "the", 
    "clubhouse", "for", "another", "adventurous", 
    "afternoon", "." };
String[] posTags = new String[] { "DT", "NNS", "VBD", 
    "VBG", "DT", "NN", "IN", "DT", "JJ", "NN", "." };
String[] lemmas = lemmatizer.lemmatize(tokens, posTags);
for (int i = 0; i < tokens.length; i++) {
    System.out.println(tokens[i] + " - " + lemmas[i]);
}

4. Upon executing the program, you will get the following output that displays each word and then its lemma:

The - the
girls - girl
were - be
leaving - leave
the - the
clubhouse - clubhouse
for - for
another - another
adventurous - adventurous
afternoon - afternoon
. - .