At the first glance it seems that the head of a noun phrase is

the deepest place in the grammar where the decision is made

whether the complete noun phrase is in singular or plural.

Regards,

Joachim

Thanks Joachim.

Finally I solved it by Stanford Tools:

for (Tree subtree : parse) {

if ((subtree.label().value().equals("NP") )) {

System.out.println(subtree.getLeaves());

System.out.println(subtree.headTerminal(headFinder,null));

}

}