[commons-text] 06/08: Add and use a package-private singleton for LongestCommonSubsequence

[ggregory]

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ggregory pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/commons-text.git

commit 0612dce660cafc4c56f42cea1cff780d36b06d46
Author: Gary Gregory <garydgreg...@gmail.com>
AuthorDate: Sat Jan 14 09:03:06 2023 -0500

    Add and use a package-private singleton for LongestCommonSubsequence
---
 src/changes/changes.xml                                            | 1 +
 .../apache/commons/text/similarity/LongestCommonSubsequence.java   | 5 +++++
 .../commons/text/similarity/LongestCommonSubsequenceDistance.java  | 7 +------
 3 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/changes/changes.xml b/src/changes/changes.xml
index b3d02cd0..c3b33d32 100644
--- a/src/changes/changes.xml
+++ b/src/changes/changes.xml
@@ -52,6 +52,7 @@ The <action> type attribute can be add,update,fix,remove.
     <action issue="TEXT-221" type="fix" dev="aherbert" due-to="Remco 
Riswick">Fix Bundle-SymbolicName to use the package name 
org.apache.commons.text</action>
     <action                  type="fix" dev="ggregory" due-to="Gary 
Gregory">Add and use a package-private singleton for RegexTokenizer.</action>
     <action                  type="fix" dev="ggregory" due-to="Gary 
Gregory">Add and use a package-private singleton for CosineSimilarity.</action>
+    <action                  type="fix" dev="ggregory" due-to="Gary 
Gregory">Add and use a package-private singleton for 
LongestCommonSubsequence.</action>
     <!-- ADD -->
     <!-- UPDATE -->
     <action                  type="update" dev="ggregory" 
due-to="Dependabot">Bump actions/cache from 3.0.8 to 3.0.10 #361, #365.</action>
diff --git 
a/src/main/java/org/apache/commons/text/similarity/LongestCommonSubsequence.java
 
b/src/main/java/org/apache/commons/text/similarity/LongestCommonSubsequence.java
index aaf05900..b91f23c0 100644
--- 
a/src/main/java/org/apache/commons/text/similarity/LongestCommonSubsequence.java
+++ 
b/src/main/java/org/apache/commons/text/similarity/LongestCommonSubsequence.java
@@ -51,6 +51,11 @@ package org.apache.commons.text.similarity;
  */
 public class LongestCommonSubsequence implements SimilarityScore<Integer> {
 
+    /**
+     * Singleton instance.
+     */
+    static final LongestCommonSubsequence INSTANCE = new 
LongestCommonSubsequence();
+
     /**
      * An implementation of "ALG B" from Hirschberg's CACM '71 paper.
      * Assuming the first input sequence is of size <code>m</code> and the 
second input sequence is of size
diff --git 
a/src/main/java/org/apache/commons/text/similarity/LongestCommonSubsequenceDistance.java
 
b/src/main/java/org/apache/commons/text/similarity/LongestCommonSubsequenceDistance.java
index 29745461..f5f5bcf9 100644
--- 
a/src/main/java/org/apache/commons/text/similarity/LongestCommonSubsequenceDistance.java
+++ 
b/src/main/java/org/apache/commons/text/similarity/LongestCommonSubsequenceDistance.java
@@ -36,11 +36,6 @@ package org.apache.commons.text.similarity;
  */
 public class LongestCommonSubsequenceDistance implements EditDistance<Integer> 
{
 
-    /**
-     * Object for calculating the longest common subsequence that we can then 
normalize in apply.
-     */
-    private final LongestCommonSubsequence longestCommonSubsequence = new 
LongestCommonSubsequence();
-
     /**
      * Calculates an edit distance between two {@code CharSequence}'s {@code 
left} and
      * {@code right} as: {@code left.length() + right.length() - 2 * LCS(left, 
right)}, where
@@ -58,7 +53,7 @@ public class LongestCommonSubsequenceDistance implements 
EditDistance<Integer> {
         if (left == null || right == null) {
             throw new IllegalArgumentException("Inputs must not be null");
         }
-        return left.length() + right.length() - 2 * 
longestCommonSubsequence.apply(left, right);
+        return left.length() + right.length() - 2 * 
LongestCommonSubsequence.INSTANCE.apply(left, right);
     }
 
 }