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[TEXT-158]: empty strings must have similarity of 1, and distance of 0 (i.e. identical) #142

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Merged
kinow merged 1 commit into from
Jul 31, 2020
+6 −2
Merged

[TEXT-158]: empty strings must have similarity of 1, and distance of 0 (i.e. identical) #142

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1 change: 1 addition & 0 deletions src/changes/changes.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@ The <action> type attribute can be add,update,fix,remove.
</properties>
<body>
<release version="1.9.1" date="202Y-MM-DD" description="Release 1.9.1. Requires Java 8.">
<action issue="TEXT-158" type="fix" dev="kinow">Incorrect values for Jaccard similarity with empty strings</action>
<action issue="TEXT-185" type="add" dev="ggregory" due-to="Larry West, Gary Gregory">Release Notes page hasn't been updated for 1.9 release yet.</action>
<action type="add" dev="ggregory" due-to="Gary Gregory">Update spotbugs.plugin.version 4.0.0 to 4.0.4.</action>
</release>
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3 changes: 3 additions & 0 deletions src/main/java/org/apache/commons/text/similarity/JaccardSimilarity.java
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Expand Up @@ -64,6 +64,9 @@ public Double apply(final CharSequence left, final CharSequence right) {
private Double calculateJaccardSimilarity(final CharSequence left, final CharSequence right) {
final int leftLength = left.length();
final int rightLength = right.length();
if (leftLength == 0 && rightLength == 0) {
return 1d;
}
if (leftLength == 0 || rightLength == 0) {
return 0d;
}
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2 changes: 1 addition & 1 deletion src/test/java/org/apache/commons/text/similarity/JaccardDistanceTest.java
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Expand Up @@ -37,7 +37,7 @@ public static void setUp() {
@Test
public void testGettingJaccardDistance() {
// Expected Jaccard distance = 1.0 - (intersect / union)
assertEquals(1.0, classBeingTested.apply("", ""));
assertEquals(0.0, classBeingTested.apply("", ""));
assertEquals(1.0, classBeingTested.apply("left", ""));
assertEquals(1.0, classBeingTested.apply("", "right"));
assertEquals(1.0 - (3.0 / 4), classBeingTested.apply("frog", "fog"));
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2 changes: 1 addition & 1 deletion src/test/java/org/apache/commons/text/similarity/JaccardSimilarityTest.java
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Expand Up @@ -37,7 +37,7 @@ public static void setUp() {
@Test
public void testGettingJaccardSimilarity() {
// Expected Jaccard similarity = (intersect / union)
assertEquals(0.0, classBeingTested.apply("", ""));
assertEquals(1.0, classBeingTested.apply("", ""));
assertEquals(0.0, classBeingTested.apply("left", ""));
assertEquals(0.0, classBeingTested.apply("", "right"));
assertEquals(3.0 / 4, classBeingTested.apply("frog", "fog"));
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