| 17 |
|
* adjustable expected concurrency for updates. This class obeys the |
| 18 |
|
* same functional specification as {@link java.util.Hashtable}, and |
| 19 |
|
* includes versions of methods corresponding to each method of |
| 20 |
< |
* <tt>Hashtable</tt> . However, even though all operations are |
| 20 |
> |
* <tt>Hashtable</tt>. However, even though all operations are |
| 21 |
|
* thread-safe, retrieval operations do <em>not</em> entail locking, |
| 22 |
|
* and there is <em>not</em> any support for locking the entire table |
| 23 |
|
* in a way that prevents all access. This class is fully |
| 24 |
|
* interoperable with <tt>Hashtable</tt> in programs that rely on its |
| 25 |
|
* thread safety but not on its synchronization details. |
| 26 |
|
* |
| 27 |
< |
* <p> Retrieval operations (including <tt>get</tt>) ordinarily |
| 28 |
< |
* overlap with update operations (including <tt>put</tt> and |
| 29 |
< |
* <tt>remove</tt>). Retrievals reflect the results of the most |
| 30 |
< |
* recently <em>completed</em> update operations holding upon their |
| 31 |
< |
* onset. For aggregate operations such as <tt>putAll</tt> and |
| 32 |
< |
* <tt>clear</tt>, concurrent retrievals may reflect insertion or |
| 27 |
> |
* <p> Retrieval operations (including <tt>get</tt>) generally do not |
| 28 |
> |
* block, so may overlap with update operations (including |
| 29 |
> |
* <tt>put</tt> and <tt>remove</tt>). Retrievals reflect the results |
| 30 |
> |
* of the most recently <em>completed</em> update operations holding |
| 31 |
> |
* upon their onset. For aggregate operations such as <tt>putAll</tt> |
| 32 |
> |
* and <tt>clear</tt>, concurrent retrievals may reflect insertion or |
| 33 |
|
* removal of only some entries. Similarly, Iterators and |
| 34 |
|
* Enumerations return elements reflecting the state of the hash table |
| 35 |
|
* at some point at or since the creation of the iterator/enumeration. |
| 36 |
< |
* They do <em>not</em> throw <tt>ConcurrentModificationException</tt>. |
| 37 |
< |
* However, Iterators are designed to be used by only one thread at a |
| 38 |
< |
* time. |
| 36 |
> |
* They do <em>not</em> throw |
| 37 |
> |
* <tt>ConcurrentModificationException</tt>. However, Iterators are |
| 38 |
> |
* designed to be used by only one thread at a time. |
| 39 |
|
* |
| 40 |
|
* <p> The allowed concurrency among update operations is guided by |
| 41 |
|
* the optional <tt>concurrencyLevel</tt> constructor argument |
| 44 |
|
* number of concurrent updates without contention. Because placement |
| 45 |
|
* in hash tables is essentially random, the actual concurrency will |
| 46 |
|
* vary. Ideally, you should choose a value to accommodate as many |
| 47 |
< |
* threads as will ever concurrently access the table. Using a |
| 47 |
> |
* threads as will ever concurrently modify the table. Using a |
| 48 |
|
* significantly higher value than you need can waste space and time, |
| 49 |
|
* and a significantly lower value can lead to thread contention. But |
| 50 |
|
* overestimates and underestimates within an order of magnitude do |
| 51 |
< |
* not usually have much noticeable impact. |
| 51 |
> |
* not usually have much noticeable impact. A value of one is |
| 52 |
> |
* appropriate when it is known that only one thread will modify |
| 53 |
> |
* and all others will only read. |
| 54 |
|
* |
| 55 |
|
* <p>This class implements all of the <em>optional</em> methods |
| 56 |
|
* of the {@link Map} and {@link Iterator} interfaces. |
