RFR 8233187: Return Empty List if 0 Copies Requested in Collections nCopies

[Kiran Ravikumar]

Hi Guys,


Please review the following optimization to nCopies method to return 
empty list and to avoid instantiating an empty CopiesList object.


JBS link : https://bugs.openjdk.java.net/browse/JDK-8233187


Patch:

diff -r f279d8a9bb78 src/java.base/share/classes/java/util/Collections.java
--- a/src/java.base/share/classes/java/util/Collections.java Wed Nov 13 
11:27:50 2019 +0000
+++ b/src/java.base/share/classes/java/util/Collections.java Thu Nov 14 
09:37:56 2019 +0000
@@ -5105,6 +5105,8 @@
      public static <T> List<T> nCopies(int n, T o) {
          if (n < 0)
              throw new IllegalArgumentException("List length = " + n);
+        if (n == 0)
+            return Collections.emptyList();
          return new CopiesList<>(n, o);
      }


Thanks,

Kiran