Optimize AbstractTypeGenerator.listKeys()

In case of an empty key definition we end up allocating
short-lived empty ArrayLists, which is not efficient. Also lists
typically have a few elements, so we end up over-allocating them.

This fixes both cases, by checking the definition first and
returning an empty list in case the definition is empty, as well
as properly allocating efficient implementation where needed.

Change-Id: I99e8843abf6040654fab96052352cbfb29590ecf
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>

diff --git a/binding/mdsal-binding-generator-impl/src/main/java/org/opendaylight/mdsal/binding/generator/impl/AbstractTypeGenerator.java b/binding/mdsal-binding-generator-impl/src/main/java/org/opendaylight/mdsal/binding/generator/impl/AbstractTypeGenerator.java
index cace43fe7963fea4f45abe2ad20e42bf189b1584..c9e43e795a2d23b749a6cdeebd843ec77480c8d6 100644 (file)
--- a/binding/mdsal-binding-generator-impl/src/main/java/org/opendaylight/mdsal/binding/generator/impl/AbstractTypeGenerator.java
+++ b/binding/mdsal-binding-generator-impl/src/main/java/org/opendaylight/mdsal/binding/generator/impl/AbstractTypeGenerator.java
@@ -51,6 +51,7 @@ import edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
 import java.util.AbstractMap.SimpleImmutableEntry;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -1788,15 +1789,19 @@ abstract class AbstractTypeGenerator {
      *         an empty list is returned.
      */
     private static List<String> listKeys(final ListSchemaNode list) {
-        final List<String> listKeys = new ArrayList<>();
-
         final List<QName> keyDefinition = list.getKeyDefinition();
-        if (keyDefinition != null) {
-            for (final QName keyDef : keyDefinition) {
-                listKeys.add(keyDef.getLocalName());
-            }
+        switch (keyDefinition.size()) {
+            case 0:
+                return Collections.emptyList();
+            case 1:
+                return Collections.singletonList(keyDefinition.get(0).getLocalName());
+            default:
+                final List<String> listKeys = new ArrayList<>(keyDefinition.size());
+                for (final QName keyDef : keyDefinition) {
+                    listKeys.add(keyDef.getLocalName());
+                }
+                return listKeys;
         }
-        return listKeys;
     }
 
     /**