| 15 |
|
* element, and wait for space to become available in the queue when |
| 16 |
|
* storing an element. |
| 17 |
|
* |
| 18 |
< |
* <p><tt>BlockingQueue</tt> methods come in four forms, with different ways |
| 18 |
> |
* <p>{@code BlockingQueue} methods come in four forms, with different ways |
| 19 |
|
* of handling operations that cannot be satisfied immediately, but may be |
| 20 |
|
* satisfied at some point in the future: |
| 21 |
|
* one throws an exception, the second returns a special value (either |
| 22 |
< |
* <tt>null</tt> or <tt>false</tt>, depending on the operation), the third |
| 22 |
> |
* {@code null} or {@code false}, depending on the operation), the third |
| 23 |
|
* blocks the current thread indefinitely until the operation can succeed, |
| 24 |
|
* and the fourth blocks for only a given maximum time limit before giving |
| 25 |
|
* up. These methods are summarized in the following table: |
| 56 |
|
* </tr> |
| 57 |
|
* </table> |
| 58 |
|
* |
| 59 |
< |
* <p>A <tt>BlockingQueue</tt> does not accept <tt>null</tt> elements. |
| 60 |
< |
* Implementations throw <tt>NullPointerException</tt> on attempts |
| 61 |
< |
* to <tt>add</tt>, <tt>put</tt> or <tt>offer</tt> a <tt>null</tt>. A |
| 62 |
< |
* <tt>null</tt> is used as a sentinel value to indicate failure of |
| 63 |
< |
* <tt>poll</tt> operations. |
| 64 |
< |
* |
| 65 |
< |
* <p>A <tt>BlockingQueue</tt> may be capacity bounded. At any given |
| 66 |
< |
* time it may have a <tt>remainingCapacity</tt> beyond which no |
| 67 |
< |
* additional elements can be <tt>put</tt> without blocking. |
| 68 |
< |
* A <tt>BlockingQueue</tt> without any intrinsic capacity constraints always |
| 69 |
< |
* reports a remaining capacity of <tt>Integer.MAX_VALUE</tt>. |
| 59 |
> |
* <p>A {@code BlockingQueue} does not accept {@code null} elements. |
| 60 |
> |
* Implementations throw {@code NullPointerException} on attempts |
| 61 |
> |
* to {@code add}, {@code put} or {@code offer} a {@code null}. A |
| 62 |
> |
* {@code null} is used as a sentinel value to indicate failure of |
| 63 |
> |
* {@code poll} operations. |
| 64 |
> |
* |
| 65 |
> |
* <p>A {@code BlockingQueue} may be capacity bounded. At any given |
| 66 |
> |
* time it may have a {@code remainingCapacity} beyond which no |
| 67 |
> |
* additional elements can be {@code put} without blocking. |
| 68 |
> |
* A {@code BlockingQueue} without any intrinsic capacity constraints always |
| 69 |
> |
* reports a remaining capacity of {@code Integer.MAX_VALUE}. |
| 70 |
|
* |
| 71 |
< |
* <p><tt>BlockingQueue</tt> implementations are designed to be used |
| 71 |
> |
* <p>{@code BlockingQueue} implementations are designed to be used |
| 72 |
|
* primarily for producer-consumer queues, but additionally support |
| 73 |
|
* the {@link java.util.Collection} interface. So, for example, it is |
| 74 |
|
* possible to remove an arbitrary element from a queue using |
| 75 |
< |
* <tt>remove(x)</tt>. However, such operations are in general |
| 75 |
> |
* {@code remove(x)}. However, such operations are in general |
| 76 |
|
* <em>not</em> performed very efficiently, and are intended for only |
| 77 |
|
* occasional use, such as when a queued message is cancelled. |
| 78 |
|
* |
| 79 |
< |
* <p><tt>BlockingQueue</tt> implementations are thread-safe. All |
| 79 |
> |
* <p>{@code BlockingQueue} implementations are thread-safe. All |
| 80 |
|
* queuing methods achieve their effects atomically using internal |
| 81 |
|
* locks or other forms of concurrency control. However, the |
| 82 |
< |
* <em>bulk</em> Collection operations <tt>addAll</tt>, |
| 83 |
< |
* <tt>containsAll</tt>, <tt>retainAll</tt> and <tt>removeAll</tt> are |
| 82 |
> |
* <em>bulk</em> Collection operations {@code addAll}, |
| 83 |
> |
* {@code containsAll}, {@code retainAll} and {@code removeAll} are |
| 84 |
|
* <em>not</em> necessarily performed atomically unless specified |
| 85 |
|
* otherwise in an implementation. So it is possible, for example, for |
| 86 |
< |
* <tt>addAll(c)</tt> to fail (throwing an exception) after adding |
| 87 |
< |
* only some of the elements in <tt>c</tt>. |
| 86 |
> |
* {@code addAll(c)} to fail (throwing an exception) after adding |
| 87 |
> |
* only some of the elements in {@code c}. |
| 88 |
|
* |
| 89 |
< |
* <p>A <tt>BlockingQueue</tt> does <em>not</em> intrinsically support |
| 89 |
> |
* <p>A {@code BlockingQueue} does <em>not</em> intrinsically support |
| 90 |
|
* any kind of "close" or "shutdown" operation to |
| 91 |
|
* indicate that no more items will be added. The needs and usage of |
| 92 |
|
* such features tend to be implementation-dependent. For example, a |
| 96 |
|
* |
| 97 |
|
* <p> |
| 98 |
|
* Usage example, based on a typical producer-consumer scenario. |
| 99 |
< |
* Note that a <tt>BlockingQueue</tt> can safely be used with multiple |
| 99 |
> |
* Note that a {@code BlockingQueue} can safely be used with multiple |
| 100 |
|
* producers and multiple consumers. |
| 101 |
|
* <pre> {@code |
| 102 |
|
* class Producer implements Runnable { |
| 152 |
|
/** |
| 153 |
|
* Inserts the specified element into this queue if it is possible to do |
| 154 |
|
* so immediately without violating capacity restrictions, returning |
| 155 |
< |
* <tt>true</tt> upon success and throwing an |
| 156 |
< |
* <tt>IllegalStateException</tt> if no space is currently available. |
| 155 |
> |
* {@code true} upon success and throwing an |
| 156 |
> |
* {@code IllegalStateException} if no space is currently available. |
| 157 |
|
* When using a capacity-restricted queue, it is generally preferable to |
| 158 |
|
* use {@link #offer(Object) offer}. |
| 159 |
|
* |
| 160 |
|
* @param e the element to add |
| 161 |
< |
* @return <tt>true</tt> (as specified by {@link Collection#add}) |
| 161 |
> |
* @return {@code true} (as specified by {@link Collection#add}) |
| 162 |
|
* @throws IllegalStateException if the element cannot be added at this |
| 163 |
|
* time due to capacity restrictions |
| 164 |
|
* @throws ClassCastException if the class of the specified element |
| 172 |
|
/** |
| 173 |
|
* Inserts the specified element into this queue if it is possible to do |
| 174 |
|
* so immediately without violating capacity restrictions, returning |
| 175 |
< |
* <tt>true</tt> upon success and <tt>false</tt> if no space is currently |
| 175 |
> |
* {@code true} upon success and {@code false} if no space is currently |
| 176 |
|
* available. When using a capacity-restricted queue, this method is |
| 177 |
|
* generally preferable to {@link #add}, which can fail to insert an |
| 178 |
|
* element only by throwing an exception. |
| 179 |
|
* |
| 180 |
|
* @param e the element to add |
| 181 |
< |
* @return <tt>true</tt> if the element was added to this queue, else |
| 182 |
< |
* <tt>false</tt> |
| 181 |
> |
* @return {@code true} if the element was added to this queue, else |
| 182 |
> |
* {@code false} |
| 183 |
|
* @throws ClassCastException if the class of the specified element |
| 184 |
|
* prevents it from being added to this queue |
| 185 |
|
* @throws NullPointerException if the specified element is null |
| 208 |
|
* |
| 209 |
|
* @param e the element to add |
| 210 |
|
* @param timeout how long to wait before giving up, in units of |
| 211 |
< |
* <tt>unit</tt> |
| 212 |
< |
* @param unit a <tt>TimeUnit</tt> determining how to interpret the |
| 213 |
< |
* <tt>timeout</tt> parameter |
| 214 |
< |
* @return <tt>true</tt> if successful, or <tt>false</tt> if |
| 211 |
> |
* {@code unit} |
| 212 |
> |
* @param unit a {@code TimeUnit} determining how to interpret the |
| 213 |
> |
* {@code timeout} parameter |
| 214 |
> |
* @return {@code true} if successful, or {@code false} if |
| 215 |
|
* the specified waiting time elapses before space is available |
| 216 |
|
* @throws InterruptedException if interrupted while waiting |
| 217 |
|
* @throws ClassCastException if the class of the specified element |
| 237 |
|
* specified wait time if necessary for an element to become available. |
| 238 |
|
* |
| 239 |
|
* @param timeout how long to wait before giving up, in units of |
| 240 |
< |
* <tt>unit</tt> |
| 241 |
< |
* @param unit a <tt>TimeUnit</tt> determining how to interpret the |
| 242 |
< |
* <tt>timeout</tt> parameter |
| 243 |
< |
* @return the head of this queue, or <tt>null</tt> if the |
| 240 |
> |
* {@code unit} |
| 241 |
> |
* @param unit a {@code TimeUnit} determining how to interpret the |
| 242 |
> |
* {@code timeout} parameter |
| 243 |
> |
* @return the head of this queue, or {@code null} if the |
| 244 |
|
* specified waiting time elapses before an element is available |
| 245 |
|
* @throws InterruptedException if interrupted while waiting |
| 246 |
|
*/ |
| 250 |
|
/** |
| 251 |
|
* Returns the number of additional elements that this queue can ideally |
| 252 |
|
* (in the absence of memory or resource constraints) accept without |
| 253 |
< |
* blocking, or <tt>Integer.MAX_VALUE</tt> if there is no intrinsic |
| 253 |
> |
* blocking, or {@code Integer.MAX_VALUE} if there is no intrinsic |
| 254 |
|
* limit. |
| 255 |
|
* |
| 256 |
|
* <p>Note that you <em>cannot</em> always tell if an attempt to insert |
| 257 |
< |
* an element will succeed by inspecting <tt>remainingCapacity</tt> |
| 257 |
> |
* an element will succeed by inspecting {@code remainingCapacity} |
| 258 |
|
* because it may be the case that another thread is about to |
| 259 |
|
* insert or remove an element. |
| 260 |
|
* |
| 264 |
|
|
| 265 |
|
/** |
| 266 |
|
* Removes a single instance of the specified element from this queue, |
| 267 |
< |
* if it is present. More formally, removes an element <tt>e</tt> such |
| 268 |
< |
* that <tt>o.equals(e)</tt>, if this queue contains one or more such |
| 267 |
> |
* if it is present. More formally, removes an element {@code e} such |
| 268 |
> |
* that {@code o.equals(e)}, if this queue contains one or more such |
| 269 |
|
* elements. |
| 270 |
< |
* Returns <tt>true</tt> if this queue contained the specified element |
| 270 |
> |
* Returns {@code true} if this queue contained the specified element |
| 271 |
|
* (or equivalently, if this queue changed as a result of the call). |
| 272 |
|
* |
| 273 |
|
* @param o element to be removed from this queue, if present |
| 274 |
< |
* @return <tt>true</tt> if this queue changed as a result of the call |
| 274 |
> |
* @return {@code true} if this queue changed as a result of the call |
| 275 |
|
* @throws ClassCastException if the class of the specified element |
| 276 |
|
* is incompatible with this queue |
| 277 |
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
| 281 |
|
boolean remove(Object o); |
| 282 |
|
|
| 283 |
|
/** |
| 284 |
< |
* Returns <tt>true</tt> if this queue contains the specified element. |
| 285 |
< |
* More formally, returns <tt>true</tt> if and only if this queue contains |
| 286 |
< |
* at least one element <tt>e</tt> such that <tt>o.equals(e)</tt>. |
| 284 |
> |
* Returns {@code true} if this queue contains the specified element. |
| 285 |
> |
* More formally, returns {@code true} if and only if this queue contains |
| 286 |
> |
* at least one element {@code e} such that {@code o.equals(e)}. |
| 287 |
|
* |
| 288 |
|
* @param o object to be checked for containment in this queue |
| 289 |
< |
* @return <tt>true</tt> if this queue contains the specified element |
| 289 |
> |
* @return {@code true} if this queue contains the specified element |
| 290 |
|
* @throws ClassCastException if the class of the specified element |
| 291 |
|
* is incompatible with this queue |
| 292 |
|
* (<a href="../Collection.html#optional-restrictions">optional</a>) |
| 300 |
|
* to the given collection. This operation may be more |
| 301 |
|
* efficient than repeatedly polling this queue. A failure |
| 302 |
|
* encountered while attempting to add elements to |
| 303 |
< |
* collection <tt>c</tt> may result in elements being in neither, |
| 303 |
> |
* collection {@code c} may result in elements being in neither, |
| 304 |
|
* either or both collections when the associated exception is |
| 305 |
|
* thrown. Attempts to drain a queue to itself result in |
| 306 |
< |
* <tt>IllegalArgumentException</tt>. Further, the behavior of |
| 306 |
> |
* {@code IllegalArgumentException}. Further, the behavior of |
| 307 |
|
* this operation is undefined if the specified collection is |
| 308 |
|
* modified while the operation is in progress. |
| 309 |
|
* |
| 324 |
|
* Removes at most the given number of available elements from |
| 325 |
|
* this queue and adds them to the given collection. A failure |
| 326 |
|
* encountered while attempting to add elements to |
| 327 |
< |
* collection <tt>c</tt> may result in elements being in neither, |
| 327 |
> |
* collection {@code c} may result in elements being in neither, |
| 328 |
|
* either or both collections when the associated exception is |
| 329 |
|
* thrown. Attempts to drain a queue to itself result in |
| 330 |
< |
* <tt>IllegalArgumentException</tt>. Further, the behavior of |
| 330 |
> |
* {@code IllegalArgumentException}. Further, the behavior of |
| 331 |
|
* this operation is undefined if the specified collection is |
| 332 |
|
* modified while the operation is in progress. |
| 333 |
|
* |
