D-Net

package eu.dnetlib.pace.clustering;

import java.util.Collection;

import java.util.List;

import java.util.Map;

import com.google.common.collect.Lists;

/**

 * The Class NgramPairs.

 */

public class NgramPairs extends Ngrams {

	/**

	 * Instantiates a new ngram pairs.

	 * 

	 * @param params

	 *            the params

	 */

	public NgramPairs(final Map<String, Integer> params) {

		super(params);

	}

	/*

	 * (non-Javadoc)

	 * 

	 * @see eu.dnetlib.pace.clustering.Ngrams#doApply(java.lang.String)

	 */

	@Override

	protected Collection<String> doApply(final String s) {

		return ngramPairs(Lists.newArrayList(getNgrams(s, param("ngramLen"), param("max") * 2, 1, 2)), param("max"));

	}

	/**

	 * Ngram pairs.

	 * 

	 * @param ngrams

	 *            the ngrams

	 * @param maxNgrams

	 *            the max ngrams

	 * @return the collection

	 */

	private Collection<String> ngramPairs(final List<String> ngrams, final int maxNgrams) {

		Collection<String> res = Lists.newArrayList();

		int j = 0;

		for (int i = 0; (i < ngrams.size()) && (res.size() < maxNgrams); i++) {

			if (++j >= ngrams.size()) {

				break;

			}

			res.add(ngrams.get(i) + ngrams.get(j));

			// System.out.println("-- " + concatNgrams);

		}

		return res;

	}

}