StefanRRichter commented on code in PR #22788:
URL: https://github.com/apache/flink/pull/22788#discussion_r1235425320
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flink-core/src/main/java/org/apache/flink/util/CollectionUtil.java:
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@@ -133,4 +140,71 @@ public static <K, V> Map<K, V> map(Map.Entry<K, V>...
entries) {
}
return Collections.unmodifiableMap(map);
}
+
+ /**
+ * Creates a new {@link HashMap} of the expected size, i.e. a hash map
that will not rehash if
+ * expectedSize many keys are inserted, considering the load factor.
+ *
+ * @param expectedSize the expected size of the created hash map.
+ * @return a new hash map instance with enough capacity for the expected
size.
+ * @param <K> the type of keys maintained by this map.
+ * @param <V> the type of mapped values.
+ */
+ public static <K, V> HashMap<K, V> newHashMapWithExpectedSize(int
expectedSize) {
+ return new HashMap<>(computeRequiredCapacity(expectedSize),
HASH_MAP_DEFAULT_LOAD_FACTOR);
+ }
+
+ /**
+ * Creates a new {@link LinkedHashMap} of the expected size, i.e. a hash
map that will not
+ * rehash if expectedSize many keys are inserted, considering the load
factor.
+ *
+ * @param expectedSize the expected size of the created hash map.
+ * @return a new hash map instance with enough capacity for the expected
size.
+ * @param <K> the type of keys maintained by this map.
+ * @param <V> the type of mapped values.
+ */
+ public static <K, V> LinkedHashMap<K, V>
newLinkedHashMapWithExpectedSize(int expectedSize) {
+ return new LinkedHashMap<>(
+ computeRequiredCapacity(expectedSize),
HASH_MAP_DEFAULT_LOAD_FACTOR);
Review Comment:
Yes, that was the plan because every place that initializes a map with the
end size to avoid rehashing is actually causing a guaranteed rehash to happen
today. But I'd do that in a separate refactoring PR.
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