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The following commit(s) were added to refs/heads/master by this push:
new 75699fc1c [COLLECTIONS-878] MapUtils.invertMap() improves HashMap
construction (#652).
75699fc1c is described below
commit 75699fc1c5e388ab06f1196cc9bebb078d30f1b5
Author: Gary Gregory <[email protected]>
AuthorDate: Wed Jun 17 22:49:44 2026 +0000
[COLLECTIONS-878] MapUtils.invertMap() improves HashMap construction
(#652).
A version of PR #652 with some refactoring and excluding the test that
doesn't actually test.
---
src/changes/changes.xml | 1 +
.../java/org/apache/commons/collections4/MapUtils.java | 6 +++++-
.../org/apache/commons/collections4/MapUtilsTest.java | 17 +++++++----------
3 files changed, 13 insertions(+), 11 deletions(-)
diff --git a/src/changes/changes.xml b/src/changes/changes.xml
index 5f0b44cdd..3f18bf12d 100644
--- a/src/changes/changes.xml
+++ b/src/changes/changes.xml
@@ -51,6 +51,7 @@
<action type="fix" dev="ggregory" due-to="Suhyeon Park, Gary Gregory"
issue="COLLECTIONS-881">MultiMapUtils.getXXX ensure safe copy (#669).</action>
<action type="fix" dev="ggregory" due-to="Dexter.k, Gary
Gregory">Re-validate entries in PredicatedMap/PredicatedCollection readObject
(#682).</action>
<action type="fix" dev="ggregory" due-to="Ruiqi Dong, Gary Gregory"
issue="COLLECTIONS-889">IndexedCollection.remove(Object) removes all values for
a non-unique index key.</action>
+ <action type="fix" dev="ggregory" due-to="Maxim Safronov, Gary Gregory"
issue="COLLECTIONS-878">MapUtils.invertMap() improves HashMap construction
(#652).</action>
<!-- ADD -->
<action type="add" dev="ggregory" due-to="Gary Gregory">Add generics to
UnmodifiableIterator for the wrapped type.</action>
<action type="add" dev="ggregory" due-to="Gary Gregory">Add a Maven
benchmark profile for JMH.</action>
diff --git a/src/main/java/org/apache/commons/collections4/MapUtils.java
b/src/main/java/org/apache/commons/collections4/MapUtils.java
index 800199dfe..10b560dd5 100644
--- a/src/main/java/org/apache/commons/collections4/MapUtils.java
+++ b/src/main/java/org/apache/commons/collections4/MapUtils.java
@@ -148,6 +148,10 @@ public class MapUtils {
return value == null ? defaultValue : value;
}
+ private static int calculateHashMapCapacity(final int numMappings) {
+ return (int) Math.ceil(numMappings / 0.75d);
+ }
+
/**
* Prints the given map with nice line breaks.
* <p>
@@ -1185,7 +1189,7 @@ public class MapUtils {
*/
public static <K, V> Map<V, K> invertMap(final Map<K, V> map) {
Objects.requireNonNull(map, "map");
- final Map<V, K> out = new HashMap<>(map.size());
+ final Map<V, K> out = new
HashMap<>(calculateHashMapCapacity(map.size()));
for (final Entry<K, V> entry : map.entrySet()) {
out.put(entry.getValue(), entry.getKey());
}
diff --git a/src/test/java/org/apache/commons/collections4/MapUtilsTest.java
b/src/test/java/org/apache/commons/collections4/MapUtilsTest.java
index 1d1efc76c..c047d497d 100644
--- a/src/test/java/org/apache/commons/collections4/MapUtilsTest.java
+++ b/src/test/java/org/apache/commons/collections4/MapUtilsTest.java
@@ -633,11 +633,10 @@ class MapUtilsTest {
private void testInvertMap(final Map<String, String> in) {
// setup
- in.put("1", "A");
- in.put("2", "B");
- in.put("3", "C");
- in.put("4", "D");
- in.put("5", "E");
+ final int entryCount = 32;
+ for (int i = 1; i <= entryCount; i++) {
+ in.put(String.valueOf(i), String.valueOf((char) ('A' + i - 1)));
+ }
final Set<String> inKeySet = new HashSet<>(in.keySet());
final Set<String> inValSet = new HashSet<>(in.values());
// invert
@@ -647,11 +646,9 @@ class MapUtilsTest {
final Set<String> outValSet = new HashSet<>(out.values());
assertEquals(inKeySet, outValSet);
assertEquals(inValSet, outKeySet);
- assertEquals("1", out.get("A"));
- assertEquals("2", out.get("B"));
- assertEquals("3", out.get("C"));
- assertEquals("4", out.get("D"));
- assertEquals("5", out.get("E"));
+ for (int i = 1; i <= entryCount; i++) {
+ assertEquals(String.valueOf((char) ('A' + i - 1)),
in.get(String.valueOf(i)));
+ }
}
@Test
