RFR: 8221473: Configuration::reads can use Set.copyOf

[Claes Redestad]

On 2019-03-26 14:33, Claes Redestad wrote:
> Hi,
> 
> replacing a lingering use of Collections.unmodifiableSet with Set.copyOf
> in java.lang.module.Configuration is a small startup optimization.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8221473

Or with this less verbose comment (suggested offline by Alan):

diff -r 5ee30b6991a7 
src/java.base/share/classes/java/lang/module/Configuration.java
--- a/src/java.base/share/classes/java/lang/module/Configuration.java 
Mon Dec 03 16:25:27 2018 +0100
+++ b/src/java.base/share/classes/java/lang/module/Configuration.java 
Tue Mar 26 14:50:55 2019 +0100
@@ -575,7 +575,8 @@
      }

      Set<ResolvedModule> reads(ResolvedModule m) {
-        return Collections.unmodifiableSet(graph.get(m));
+        // The sets stored in the graph are already immutable sets
+        return Set.copyOf(graph.get(m));
      }

      /**