package jboost.examples.ngram;/** * This is the class for sparse ngrams, i.e., all ngrams up to a given * length, including those with wildcards. * * @author Rob Schapire (rewritten by Aaron Arvey) */public class SparseNgram extends AbstractNgram {    /** current ngram pattern */    private int n = 1;            /** stopping position for constructing ngrams */     private int end;          /**     * Constructor.  ngrams will be constructed from string s and have     * length up to the given size.  The given size cannot exceed 25     * for overflow reasons (really its 31, but we use 25 out of     * paranoia).     * @param s string from which ngrams are constructed     * @param size maximum size of all ngrams returned     */    public SparseNgram(String s, int size) {	super(s);	if (size > 25) {	    throw new IllegalArgumentException("cannot have window size bigger "					       + "than 25 in SparseNgram"); 	}	enumer = new PatternNgram(words, new boolean[] {true});	end = 1 << size;    }    public boolean hasMoreElements() {	if (n >= end)	    return false;	while (!enumer.hasMoreElements() && (n += 2) < end) {	    int pos = 0;	    for (int i = n; i != 0; i >>= 1)		pos++;	    boolean[] pat = new boolean[pos];	    pos = 0;	    for (int i = n; i != 0; i >>= 1) {		pat[pos] = ((i & 1) != 0);		pos++;	    }	    enumer = new PatternNgram(words, pat);	}	return (n < end);    }}