org.apache.commons.text.similarity.HammingDistance Maven / Gradle / Ivy
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/*
* 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.
*
*
* For further explanation about the Hamming Distance, take a look at its Wikipedia page at https://en.wikipedia.org/wiki/Hamming_distance.
*
*
* @since 1.0
*/
public class HammingDistance implements EditDistance {
/**
* Computes the Hamming Distance between two strings with the same length.
*
*
* 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.
*
*
*
* Since the Hamming Distance can only be calculated between strings of equal length, input of different lengths will throw IllegalArgumentException
*
*
*
* distance.apply("", "") = 0
* distance.apply("pappa", "pappa") = 0
* distance.apply("1011101", "1011111") = 1
* distance.apply("ATCG", "ACCC") = 2
* distance.apply("karolin", "kerstin" = 3
*
*
* @param left the first input, must not be null.
* @param right the second input, 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(final CharSequence left, final CharSequence right) {
return apply(SimilarityInput.input(left), SimilarityInput.input(right));
}
/**
* Computes the Hamming Distance between two strings with the same length.
*
*
* 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.
*
*
* Since the Hamming Distance can only be calculated between strings of equal length, input of different lengths will throw IllegalArgumentException
*
*
*
* distance.apply("", "") = 0
* distance.apply("pappa", "pappa") = 0
* distance.apply("1011101", "1011111") = 1
* distance.apply("ATCG", "ACCC") = 2
* distance.apply("karolin", "kerstin" = 3
*
*
* @param The type of similarity score unit.
* @param left the first input, must not be null.
* @param right the second input, must not be null.
* @return distance.
* @throws IllegalArgumentException if either input is {@code null} or if they do not have the same length.
* @since 1.13.0
*/
public Integer apply(final SimilarityInput left, final SimilarityInput right) {
if (left == null || right == null) {
throw new IllegalArgumentException("SimilarityInput must not be null");
}
if (left.length() != right.length()) {
throw new IllegalArgumentException("SimilarityInput must have the same length");
}
int distance = 0;
for (int i = 0; i < left.length(); i++) {
if (!left.at(i).equals(right.at(i))) {
distance++;
}
}
return distance;
}
}