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8245677: Optimize lookups in empty HashMaps

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Reviewed-by: jlaskey, redestad
This commit is contained in:
Christoph Dreis 2020-05-25 22:21:45 +02:00 committed by Claes Redestad
parent e04e052889
commit 742d35e08a
2 changed files with 16 additions and 16 deletions
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26
src/java.base/share/classes/java/util/HashMap.java
View File

@ -555,20 +555,19 @@ public class HashMap<K,V> extends AbstractMap<K,V>
*/ */
public V get(Object key) { public V get(Object key) {
Node<K,V> e; Node<K,V> e;
return (e = getNode(hash(key), key)) == null ? null : e.value; return (e = getNode(key)) == null ? null : e.value;
} }
/** /**
* Implements Map.get and related methods. * Implements Map.get and related methods.
* *
* @param hash hash for key
* @param key the key * @param key the key
* @return the node, or null if none * @return the node, or null if none
*/ */
final Node<K,V> getNode(int hash, Object key) { final Node<K,V> getNode(Object key) {
Node<K,V>[] tab; Node<K,V> first, e; int n; K k; Node<K,V>[] tab; Node<K,V> first, e; int n, hash; K k;
if ((tab = table) != null && (n = tab.length) > 0 && if ((tab = table) != null && (n = tab.length) > 0 &&
(first = tab[(n - 1) & hash]) != null) { (first = tab[(n - 1) & (hash = hash(key))]) != null) {
if (first.hash == hash && // always check first node if (first.hash == hash && // always check first node
((k = first.key) == key || (key != null && key.equals(k)))) ((k = first.key) == key || (key != null && key.equals(k))))
return first; return first;
@ -594,7 +593,7 @@ public class HashMap<K,V> extends AbstractMap<K,V>
* key. * key.
*/ */
public boolean containsKey(Object key) { public boolean containsKey(Object key) {
return getNode(hash(key), key) != null; return getNode(key) != null;
} }
/** /**
@ -1105,7 +1104,7 @@ public class HashMap<K,V> extends AbstractMap<K,V>
return false; return false;
Map.Entry<?,?> e = (Map.Entry<?,?>) o; Map.Entry<?,?> e = (Map.Entry<?,?>) o;
Object key = e.getKey(); Object key = e.getKey();
Node<K,V> candidate = getNode(hash(key), key); Node<K,V> candidate = getNode(key);
return candidate != null && candidate.equals(e); return candidate != null && candidate.equals(e);
} }
public final boolean remove(Object o) { public final boolean remove(Object o) {
@ -1141,7 +1140,7 @@ public class HashMap<K,V> extends AbstractMap<K,V>
@Override @Override
public V getOrDefault(Object key, V defaultValue) { public V getOrDefault(Object key, V defaultValue) {
Node<K,V> e; Node<K,V> e;
return (e = getNode(hash(key), key)) == null ? defaultValue : e.value; return (e = getNode(key)) == null ? defaultValue : e.value;
} }
@Override @Override
@ -1157,7 +1156,7 @@ public class HashMap<K,V> extends AbstractMap<K,V>
@Override @Override
public boolean replace(K key, V oldValue, V newValue) { public boolean replace(K key, V oldValue, V newValue) {
Node<K,V> e; V v; Node<K,V> e; V v;
if ((e = getNode(hash(key), key)) != null && if ((e = getNode(key)) != null &&
((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) { ((v = e.value) == oldValue || (v != null && v.equals(oldValue)))) {
e.value = newValue; e.value = newValue;
afterNodeAccess(e); afterNodeAccess(e);
@ -1169,7 +1168,7 @@ public class HashMap<K,V> extends AbstractMap<K,V>
@Override @Override
public V replace(K key, V value) { public V replace(K key, V value) {
Node<K,V> e; Node<K,V> e;
if ((e = getNode(hash(key), key)) != null) { if ((e = getNode(key)) != null) {
V oldValue = e.value; V oldValue = e.value;
e.value = value; e.value = value;
afterNodeAccess(e); afterNodeAccess(e);
@ -1260,8 +1259,7 @@ public class HashMap<K,V> extends AbstractMap<K,V>
if (remappingFunction == null) if (remappingFunction == null)
throw new NullPointerException(); throw new NullPointerException();
Node<K,V> e; V oldValue; Node<K,V> e; V oldValue;
int hash = hash(key); if ((e = getNode(key)) != null &&
if ((e = getNode(hash, key)) != null &&
(oldValue = e.value) != null) { (oldValue = e.value) != null) {
int mc = modCount; int mc = modCount;
V v = remappingFunction.apply(key, oldValue); V v = remappingFunction.apply(key, oldValue);
@ -1271,8 +1269,10 @@ public class HashMap<K,V> extends AbstractMap<K,V>
afterNodeAccess(e); afterNodeAccess(e);
return v; return v;
} }
else else {
int hash = hash(key);
removeNode(hash, key, null, false, true); removeNode(hash, key, null, false, true);
}
} }
return null; return null;
} }

6
src/java.base/share/classes/java/util/LinkedHashMap.java
View File

@ -438,7 +438,7 @@ public class LinkedHashMap<K,V>
*/ */
public V get(Object key) { public V get(Object key) {
Node<K,V> e; Node<K,V> e;
if ((e = getNode(hash(key), key)) == null) if ((e = getNode(key)) == null)
return null; return null;
if (accessOrder) if (accessOrder)
afterNodeAccess(e); afterNodeAccess(e);
@ -450,7 +450,7 @@ public class LinkedHashMap<K,V>
*/ */
public V getOrDefault(Object key, V defaultValue) { public V getOrDefault(Object key, V defaultValue) {
Node<K,V> e; Node<K,V> e;
if ((e = getNode(hash(key), key)) == null) if ((e = getNode(key)) == null)
return defaultValue; return defaultValue;
if (accessOrder) if (accessOrder)
afterNodeAccess(e); afterNodeAccess(e);
@ -685,7 +685,7 @@ public class LinkedHashMap<K,V>
return false; return false;
Map.Entry<?,?> e = (Map.Entry<?,?>) o; Map.Entry<?,?> e = (Map.Entry<?,?>) o;
Object key = e.getKey(); Object key = e.getKey();
Node<K,V> candidate = getNode(hash(key), key); Node<K,V> candidate = getNode(key);
return candidate != null && candidate.equals(e); return candidate != null && candidate.equals(e);
} }
public final boolean remove(Object o) { public final boolean remove(Object o) {