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Stanford CoreNLP provides a set of natural language analysis tools which can take raw English language text input and give the base forms of words, their parts of speech, whether they are names of companies, people, etc., normalize dates, times, and numeric quantities, mark up the structure of sentences in terms of phrases and word dependencies, and indicate which noun phrases refer to the same entities. It provides the foundational building blocks for higher level text understanding applications.

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package edu.stanford.nlp.util;

import java.util.*;

/**
 * Implements a finite beam, taking a comparator (default is
 * ScoredComparator.ASCENDING_COMPARATOR, the MAX object according to
 * the comparator is the one to be removed) and a beam size on
 * construction (default is 100).  Adding an object may cause the
 * worst-scored object to be removed from the beam (and that object
 * may well be the newly added object itself).
 *
 * @author Dan Klein
 * @version 1.0
 */
public class Beam extends AbstractSet {

  protected final int maxBeamSize;
  protected final Heap elements;

  public int capacity() {
    return maxBeamSize;
  }

  @Override
  public int size() {
    return elements.size();
  }

  @Override
  public Iterator iterator() {
    return asSortedList().iterator();
  }

  public List asSortedList() {
    LinkedList list = new LinkedList<>();
    for (Iterator i = elements.iterator(); i.hasNext();) {
      list.addFirst(i.next());
    }
    return list;
  }

  @Override
  public boolean add(T o) {
    boolean added = true;
    elements.add(o);
    while (size() > capacity()) {
      Object dumped = elements.extractMin();
      if (dumped.equals(o)) {
        added = false;
      }
    }
    return added;
  }

  @Override
  public boolean remove(Object o) {
    //return elements.remove(o);
    throw new UnsupportedOperationException();
  }

  public Beam() {
    this(100);
  }

  // TODO dlwh: This strikes me as unsafe even now.
  public Beam(int maxBeamSize) {
    this(maxBeamSize, ErasureUtils.>uncheckedCast(ScoredComparator.ASCENDING_COMPARATOR));
  }

  public Beam(int maxBeamSize, Comparator cmp) {
    elements = new ArrayHeap<>(cmp);
    this.maxBeamSize = maxBeamSize;
  }

  /*
   * This is a test
  public static void main(String[] args) {
    Beam b = new Beam(2, ScoredComparator.ASCENDING_COMPARATOR);
    b.add(new ScoredObject("1", 1.0));
    b.add(new ScoredObject("2", 2.0));
    b.add(new ScoredObject("3", 3.0));
    b.add(new ScoredObject("0", 0.0));
    for (Iterator bI = b.iterator(); bI.hasNext();) {
      ScoredObject sO = bI.next();
      System.out.println(sO);
    }
  }
  */

}