[GitHub] aherbert commented on a change in pull request #103: TEXT-126: Adding Sorensen-Dice similarity algoritham

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aherbert commented on a change in pull request #103: TEXT-126: Adding Sorensen-Dice similarity algoritham
URL: https://github.com/apache/commons-text/pull/103#discussion_r261708871
 
 

 ##########
 File path: src/main/java/org/apache/commons/text/similarity/SorensenDicesSimilarity.java
 ##########
 @@ -0,0 +1,74 @@
+/*
+ * 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;
+
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ *
+ * @since 1.7
+ */
+public class SorensenDicesSimilarity implements SimilarityScore<Double> {
+
+    /**
+     * @param left  the first CharSequence, must not be null
+     * @param right the second CharSequence, must not be null
+     * @return result similarity
+     * @throws IllegalArgumentException if either CharSequence input is {@code null}
+     */
+
+    @Override
+    public Double apply(final CharSequence left, final CharSequence right) {
+
+        if (left == null || right == null) {
+            throw new IllegalArgumentException("CharSequences must not be null");
+        }
+
+        if (left.equals(right)) {
+            return 1d;
+        }
+
+        if ("".equals(left) || "".equals(right)) {
 
 Review comment:
   Not a good benchmark since you only tested empty strings and the same string at that. This is testing the reference is the same (effectively String.equals(String s) { return this == s; }) and not even looking at the characters in the string.
   
   What about strings that are 10, 20, 100+ characters long?
   
   Plus what about CharSequence where String.equals will not work? Did you look at String.contentEquals?
   

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