code: /*
   * #%L
   * Simmetrics Core
   * %%
   * Copyright (C) 2014 - 2016 Simmetrics Authors
   * %%
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   * 
   *      http://www.apache.org/licenses/LICENSE-2.0
   * 
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   * #L%
   */
  package org.simmetrics;
  
  /**
   * Measures the unnormalized dissimilarity between two Strings. The
   * measurement results in a non-negative value. A value of zero indicates that
   * the objects are similar.
   * <p>
   * The distance measure should be consistent with equals such that
   * {@code a.equals(b) =>
   * distance(a,b) == 0.0}.
   * <p>
   * The distance measure should be reflexive such that
   * {@code distance(a,a) == 0.0}.
   * <p>
   * The distance measure should be symmetric such that
   * {@code distance(a,b) == distance(b,a)}.
   * <p>
   * The distance measure may be transitive such that
   * {@code distance(a, c) ≤ distance(a, b) +
   * distance(b, c)}
   * <p>
   * The distance measure may satisfy the coincidence axiom such that
   * {@code compare(a, b) = 0 if and only if a.equals(b)}
   * 
   * @see <a href="https://en.wikipedia.org/wiki/Metric_(mathematics)">Wikipedia -
   *      Metric</a>
   */
  public interface StringDistance extends Distance<String> {
  	/**
  	 * Measures the distance between string a and b. The measurement results in a
  	 * non-negative value. A value of {@code 0.0} indicates that {@code a} and
  	 * {@code b} are similar.
  	 * 
  	 * @param a
  	 *            string a to compare
  	 * @param b
  	 *            string b to compare
  	 * @return a non-negative value
  	 * @throws NullPointerException
  	 *             when either a or b is null
  	 */
  	@Override
  	float distance(String a, String b);
  }
  