| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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. |
| */ |
| package org.apache.commons.text.similarity; |
| |
| /** |
| * The hamming distance between two strings of equal length is the number of |
| * positions at which the corresponding symbols are different. |
| * |
| * <p> |
| * For further explanation about the Hamming Distance, take a look at its |
| * Wikipedia page at http://en.wikipedia.org/wiki/Hamming_distance. |
| * </p> |
| * |
| * @since 1.0 |
| */ |
| public class HammingDistance implements EditDistance<Integer> { |
| |
| /** |
| * Find the Hamming Distance between two strings with the same |
| * length. |
| * |
| * <p>The distance starts with zero, and for each occurrence of a |
| * different character in either String, it increments the distance |
| * by 1, and finally return its value.</p> |
| * |
| * <p>Since the Hamming Distance can only be calculated between strings of equal length, input of different lengths |
| * will throw IllegalArgumentException</p> |
| * |
| * <pre> |
| * distance.apply("", "") = 0 |
| * distance.apply("pappa", "pappa") = 0 |
| * distance.apply("1011101", "1011111") = 1 |
| * distance.apply("ATCG", "ACCC") = 2 |
| * distance.apply("karolin", "kerstin" = 3 |
| * </pre> |
| * |
| * @param left the first CharSequence, must not be null |
| * @param right the second CharSequence, must not be null |
| * @return distance |
| * @throws IllegalArgumentException if either input is {@code null} or |
| * if they do not have the same length |
| */ |
| @Override |
| public Integer apply(CharSequence left, CharSequence right) { |
| if (left == null || right == null) { |
| throw new IllegalArgumentException("Strings must not be null"); |
| } |
| |
| if (left.length() != right.length()) { |
| throw new IllegalArgumentException("Strings must have the same length"); |
| } |
| |
| int distance = 0; |
| |
| for (int i = 0; i < left.length(); i++) { |
| if (left.charAt(i) != right.charAt(i)) { |
| distance++; |
| } |
| } |
| |
| return distance; |
| } |
| |
| } |