Add back IntObjectMap.values(Class<V>)

Motivation:

Although the new IntObjectMap.values() that returns Collection is
useful, the removed values(Class<V>) that returns an array is also
useful. It's also good for backward compatibility.

Modifications:

- Add IntObjectMap.values(Class<V>) back
- Miscellaneous improvements
  - Cache the collection returned by IntObjectHashMap.values()
  - Inspector warnings
- Update the IntObjectHashMapTest to test both values()

Result:

- Backward compatibility
- Potential performance improvement of values()

common/src/main/java/io/netty/util/collection/IntObjectHashMap.java

@@ -15,6 +15,7 @@
 
 package io.netty.util.collection;
 
+import java.lang.reflect.Array;
 import java.util.AbstractCollection;
 import java.util.Arrays;
 import java.util.Collection;
@@ -51,6 +52,7 @@ public class IntObjectHashMap<V> implements IntObjectMap<V>, Iterable<IntObjectM
 
     private int[] keys;
     private V[] values;
+    private Collection<V> valueCollection;
     private int size;
 
     public IntObjectHashMap() {
@@ -78,7 +80,7 @@ public class IntObjectHashMap<V> implements IntObjectMap<V>, Iterable<IntObjectM
 
         // Allocate the arrays.
         keys = new int[capacity];
-        @SuppressWarnings({ "unchecked", })
+        @SuppressWarnings({ "unchecked", "SuspiciousArrayCast" })
         V[] temp = (V[]) new Object[capacity];
         values = temp;
 
@@ -190,9 +192,9 @@ public class IntObjectHashMap<V> implements IntObjectMap<V>, Iterable<IntObjectM
     @Override
     public boolean containsValue(V value) {
         V v = toInternal(value);
-        for (int i = 0; i < values.length; ++i) {
+        for (V value1 : values) {
             // The map supports null values; this will be matched as NULL_VALUE.equals(NULL_VALUE).
-            if (values[i] != null && values[i].equals(v)) {
+            if (value1 != null && value1.equals(v)) {
                 return true;
             }
         }
@@ -221,9 +223,24 @@ public class IntObjectHashMap<V> implements IntObjectMap<V>, Iterable<IntObjectM
         return outKeys;
     }
 
+    @Override
+    public V[] values(Class<V> clazz) {
+        @SuppressWarnings("unchecked")
+        V[] outValues = (V[]) Array.newInstance(clazz, size());
+        int targetIx = 0;
+        for (V value : values) {
+            if (value != null) {
+                outValues[targetIx++] = value;
+            }
+        }
+        return outValues;
+    }
+
     @Override
     public Collection<V> values() {
-        return new AbstractCollection<V>() {
+        Collection<V> valueCollection = this.valueCollection;
+        if (valueCollection == null) {
+            this.valueCollection = valueCollection = new AbstractCollection<V>() {
                 @Override
                 public Iterator<V> iterator() {
                     return new Iterator<V>() {
@@ -252,13 +269,16 @@ public class IntObjectHashMap<V> implements IntObjectMap<V>, Iterable<IntObjectM
             };
         }
 
+        return valueCollection;
+    }
+
     @Override
     public int hashCode() {
         // Hashcode is based on all non-zero, valid keys. We have to scan the whole keys
         // array, which may have different lengths for two maps of same size(), so the
         // capacity cannot be used as input for hashing but the size can.
         int hash = size;
-        for (int i = 0; i < keys.length; ++i) {
+        for (int key : keys) {
             // 0 can be a valid key or unused slot, but won't impact the hashcode in either case.
             // This way we can use a cheap loop without conditionals, or hard-to-unroll operations,
             // or the devastatingly bad memory locality of visiting value objects.
@@ -266,7 +286,7 @@ public class IntObjectHashMap<V> implements IntObjectMap<V>, Iterable<IntObjectM
             // of terms, only their values; since the map is an unordered collection and
             // entries can end up in different positions in different maps that have the same
             // elements, but with different history of puts/removes, due to conflicts.
-            hash ^= keys[i];
+            hash ^= key;
         }
         return hash;
     }
@@ -380,8 +400,8 @@ public class IntObjectHashMap<V> implements IntObjectMap<V>, Iterable<IntObjectM
         int nextFree = index;
         for (int i = probeNext(index); values[i] != null; i = probeNext(i)) {
             int bucket = hashIndex(keys[i]);
-            if ((i < bucket && (bucket <= nextFree || nextFree <= i))
+            if (i < bucket && (bucket <= nextFree || nextFree <= i) ||
-                    || (bucket <= nextFree && nextFree <= i)) {
+                bucket <= nextFree && nextFree <= i) {
                 // Move the displaced entry "back" to the first available position.
                 keys[nextFree] = keys[i];
                 values[nextFree] = values[i];
@@ -412,7 +432,7 @@ public class IntObjectHashMap<V> implements IntObjectMap<V>, Iterable<IntObjectM
         V[] oldVals = values;
 
         keys = new int[newCapacity];
-        @SuppressWarnings({ "unchecked" })
+        @SuppressWarnings({ "unchecked", "SuspiciousArrayCast" })
         V[] temp = (V[]) new Object[newCapacity];
         values = temp;
 
@@ -425,8 +445,7 @@ public class IntObjectHashMap<V> implements IntObjectMap<V>, Iterable<IntObjectM
                 // Inlined put(), but much simpler: we don't need to worry about
                 // duplicated keys, growing/rehashing, or failing to insert.
                 int oldKey = oldKeys[i];
-                int startIndex = hashIndex(oldKey);
+                int index = hashIndex(oldKey);
-                int index = startIndex;
 
                 for (;;) {
                     if (values[index] == null) {

common/src/main/java/io/netty/util/collection/IntObjectMap.java

@@ -114,5 +114,10 @@ public interface IntObjectMap<V> {
     /**
      * Gets the values contained in this map.
      */
+    V[] values(Class<V> clazz);
+
+    /**
+     * Gets the values contatins in this map as a {@link Collection}.
+     */
     Collection<V> values();
 }

common/src/main/java/io/netty/util/collection/PrimitiveCollections.java

@@ -106,6 +106,11 @@ public final class PrimitiveCollections {
             return EmptyArrays.EMPTY_INTS;
         }
 
+        @Override
+        public Object[] values(Class<Object> clazz) {
+            return EmptyArrays.EMPTY_OBJECTS;
+        }
+
         @Override
         public Collection<Object> values() {
             return Collections.emptyList();
@@ -185,6 +190,11 @@ public final class PrimitiveCollections {
             return map.keys();
         }
 
+        @Override
+        public V[] values(Class<V> clazz) {
+            return map.values(clazz);
+        }
+
         @Override
         public Collection<V> values() {
             return map.values();

common/src/test/java/io/netty/util/collection/IntObjectHashMapTest.java

@@ -14,12 +14,6 @@
  */
 package io.netty.util.collection;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
-import static org.junit.Assert.assertNull;
-import static org.junit.Assert.assertSame;
-import static org.junit.Assert.assertTrue;
-
 import org.junit.Before;
 import org.junit.Test;
 
@@ -30,6 +24,8 @@ import java.util.HashSet;
 import java.util.Random;
 import java.util.Set;
 
+import static org.junit.Assert.*;
+
 /**
  * Tests for {@link IntObjectHashMap}.
  */
@@ -281,19 +277,28 @@ public class IntObjectHashMapTest {
         map.put(4, new Value("v4"));
         map.remove(4);
 
-        Collection<Value> values = map.values();
+        // Ensure values() return all values.
-        assertEquals(3, values.size());
-
         Set<Value> expected = new HashSet<Value>();
+        Set<Value> actual = new HashSet<Value>();
+
         expected.add(v1);
         expected.add(v2);
         expected.add(v3);
 
-        Set<Value> found = new HashSet<Value>();
+        Value[] valueArray = map.values(Value.class);
-        for (Value value : values) {
+        assertEquals(3, valueArray.length);
-            assertTrue(found.add(value));
+        for (Value value : valueArray) {
+            assertTrue(actual.add(value));
         }
-        assertEquals(expected, found);
+        assertEquals(expected, actual);
+        actual.clear();
+
+        Collection<Value> valueCollection = map.values();
+        assertEquals(3, valueCollection.size());
+        for (Value value : valueCollection) {
+            assertTrue(actual.add(value));
+        }
+        assertEquals(expected, actual);
     }
 
     @Test
@@ -319,14 +324,14 @@ public class IntObjectHashMapTest {
             map2.put(key, key);
         }
         assertEquals(map1.hashCode(), map2.hashCode());
-        assertTrue(map1.equals(map2));
+        assertEquals(map1, map2);
         // Remove one "middle" element, maps should now be non-equals.
         int[] keys = map1.keys();
         map2.remove(keys[50]);
         assertFalse(map1.equals(map2));
         // Put it back; will likely be in a different position, but maps will be equal again.
         map2.put(keys[50], map1.keys()[50]);
-        assertTrue(map1.equals(map2));
+        assertEquals(map1, map2);
         assertEquals(map1.hashCode(), map2.hashCode());
         // Make map2 have one extra element, will be non-equal.
         map2.put(1000, 1000);
@@ -340,7 +345,7 @@ public class IntObjectHashMapTest {
             map2.put(key, key);
         }
         assertEquals(map1.hashCode(), map2.hashCode());
-        assertTrue(map1.equals(map2));
+        assertEquals(map1, map2);
     }
 
     @Test