leventov commented on a change in pull request #8059: Refactoring to use
`CollectionUtils.mapValues`
URL: https://github.com/apache/incubator-druid/pull/8059#discussion_r303093404
##########
File path: core/src/main/java/org/apache/druid/utils/CollectionUtils.java
##########
@@ -83,6 +86,17 @@ public int size()
return result;
}
+ /**
+ * Returns a transformed map from the given input map where the key is
modified based on the given keyMapper
+ * function.
+ */
+ public static <K, V, K2> Map<K2, V> mapKeys(Map<K, V> map, Function<K, K2>
keyMapper)
+ {
+ final Map<K2, V> result = Maps.newHashMapWithExpectedSize(map.size());
+ map.forEach((k, v) -> result.put(keyMapper.apply(k), v));
Review comment:
I think it's better if this method fails with IllegalStateException on keys
collisions if the key mapper is not a bijection, similar to
[`ImmutableMap.Builder`](https://guava.dev/releases/19.0/api/docs/com/google/common/collect/ImmutableMap.Builder.html).
This should also be reflected in the method's javadoc.
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