ICU-13620 Adding more comments on CollectionSet.

X-SVN-Rev: 41302

diff --git a/icu4j/main/classes/core/src/com/ibm/icu/impl/CollectionSet.java b/icu4j/main/classes/core/src/com/ibm/icu/impl/CollectionSet.java
index 4f7eb9ce789b2fac27dc0d895764209ca3ce9ee8..095661929b860422e596d6e539ac96e7feff7397 100644 (file)
--- a/icu4j/main/classes/core/src/com/ibm/icu/impl/CollectionSet.java
+++ b/icu4j/main/classes/core/src/com/ibm/icu/impl/CollectionSet.java
@@ -9,6 +9,10 @@ import java.util.Set;
 /**
  * A wrapper around java.util.Collection that implements java.util.Set. This class keeps a pointer to the
  * Collection and does not persist any data on its own.
+ *
+ * Useful when you need a Set but creating a HashSet is too expensive.
+ *
+ * IMPORTANT: The elements of the Collection *must* be unique! This class does not check.
  */
 public class CollectionSet<E> implements Set<E> {