src/share/classes/java/util/concurrent/ConcurrentMap.java
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rev 6858 : 8004518: Add in-place operations to Map
8010122: Add defaults for ConcurrentMap operations to Map
Reviewed-by: darcy, briangoetz, mduigou, dholmes, ulfzibis
Contributed-by: Doug Lea <dl at cs.oswego.edu>, Henry Jen <henry.jen@oracle.com>, Akhil Arora <akhil.arora@oracle.com>, Peter Levart <peter.levart@gmail.com>
*** 36,46 ****
package java.util.concurrent;
import java.util.Map;
/**
* A {@link java.util.Map} providing additional atomic
! * <tt>putIfAbsent</tt>, <tt>remove</tt>, and <tt>replace</tt> methods.
*
* <p>Memory consistency effects: As with other concurrent
* collections, actions in a thread prior to placing an object into a
* {@code ConcurrentMap} as a key or value
* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
--- 36,46 ----
package java.util.concurrent;
import java.util.Map;
/**
* A {@link java.util.Map} providing additional atomic
! * {@code putIfAbsent}, {@code remove}, and {@code replace} methods.
*
* <p>Memory consistency effects: As with other concurrent
* collections, actions in a thread prior to placing an object into a
* {@code ConcurrentMap} as a key or value
* <a href="package-summary.html#MemoryVisibility"><i>happen-before</i></a>
*** 55,64 ****
--- 55,79 ----
* @author Doug Lea
* @param <K> the type of keys maintained by this map
* @param <V> the type of mapped values
*/
public interface ConcurrentMap<K, V> extends Map<K, V> {
+
+ /**
+ * {@inheritDoc}
+ *
+ * @implNote This implementation assumes that the ConcurrentMap cannot
+ * contain null values and get() returning null unambiguously means no
+ * mapping is present. Implementations which support null values must
+ * override this default implementation.
+ */
+ @Override
+ default V getOrDefault(Object key, V defaultValue) {
+ V v;
+ return (null != (v = get(key))) ? v : defaultValue;
+ }
+
/**
* If the specified key is not already associated
* with a value, associate it with the given value.
* This is equivalent to
* <pre> {@code
*** 89,110 ****
/**
* Removes the entry for a key only if currently mapped to a given value.
* This is equivalent to
* <pre> {@code
! * if (map.containsKey(key) && map.get(key).equals(value)) {
* map.remove(key);
* return true;
* } else
* return false;}</pre>
*
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param value value expected to be associated with the specified key
! * @return <tt>true</tt> if the value was removed
! * @throws UnsupportedOperationException if the <tt>remove</tt> operation
* is not supported by this map
* @throws ClassCastException if the key or value is of an inappropriate
* type for this map
* (<a href="../Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified key or value is null,
--- 104,125 ----
/**
* Removes the entry for a key only if currently mapped to a given value.
* This is equivalent to
* <pre> {@code
! * if (map.containsKey(key) && Objects.equals(map.get(key), value)) {
* map.remove(key);
* return true;
* } else
* return false;}</pre>
*
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param value value expected to be associated with the specified key
! * @return {@code true} if the value was removed
! * @throws UnsupportedOperationException if the {@code remove} operation
* is not supported by this map
* @throws ClassCastException if the key or value is of an inappropriate
* type for this map
* (<a href="../Collection.html#optional-restrictions">optional</a>)
* @throws NullPointerException if the specified key or value is null,
*** 115,137 ****
/**
* Replaces the entry for a key only if currently mapped to a given value.
* This is equivalent to
* <pre> {@code
! * if (map.containsKey(key) && map.get(key).equals(oldValue)) {
* map.put(key, newValue);
* return true;
* } else
* return false;}</pre>
*
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param oldValue value expected to be associated with the specified key
* @param newValue value to be associated with the specified key
! * @return <tt>true</tt> if the value was replaced
! * @throws UnsupportedOperationException if the <tt>put</tt> operation
* is not supported by this map
* @throws ClassCastException if the class of a specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if a specified key or value is null,
* and this map does not permit null keys or values
--- 130,152 ----
/**
* Replaces the entry for a key only if currently mapped to a given value.
* This is equivalent to
* <pre> {@code
! * if (map.containsKey(key) && Objects.equals(map.get(key), oldValue)) {
* map.put(key, newValue);
* return true;
* } else
* return false;}</pre>
*
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param oldValue value expected to be associated with the specified key
* @param newValue value to be associated with the specified key
! * @return {@code true} if the value was replaced
! * @throws UnsupportedOperationException if the {@code put} operation
* is not supported by this map
* @throws ClassCastException if the class of a specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if a specified key or value is null,
* and this map does not permit null keys or values
*** 152,166 ****
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param value value to be associated with the specified key
* @return the previous value associated with the specified key, or
! * <tt>null</tt> if there was no mapping for the key.
! * (A <tt>null</tt> return can also indicate that the map
! * previously associated <tt>null</tt> with the key,
* if the implementation supports null values.)
! * @throws UnsupportedOperationException if the <tt>put</tt> operation
* is not supported by this map
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if the specified key or value is null,
* and this map does not permit null keys or values
--- 167,181 ----
* except that the action is performed atomically.
*
* @param key key with which the specified value is associated
* @param value value to be associated with the specified key
* @return the previous value associated with the specified key, or
! * {@code null} if there was no mapping for the key.
! * (A {@code null} return can also indicate that the map
! * previously associated {@code null} with the key,
* if the implementation supports null values.)
! * @throws UnsupportedOperationException if the {@code put} operation
* is not supported by this map
* @throws ClassCastException if the class of the specified key or value
* prevents it from being stored in this map
* @throws NullPointerException if the specified key or value is null,
* and this map does not permit null keys or values