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>
(cherry picked from commit efe9042ecb51521850d9b90f4d8460a35c9bd9ea)

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 bace161c8f6971f4b114196ad5606ac43eca4581..53d214f4140078ddf2342b3040d2fe2c474260d2 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;
     }
 
     /**