1 |
/* |
2 |
* Written by Doug Lea with assistance from members of JCP JSR-166 |
3 |
* Expert Group and released to the public domain, as explained at |
4 |
* http://creativecommons.org/publicdomain/zero/1.0/ |
5 |
*/ |
6 |
|
7 |
package jsr166x; // XXX This belongs in java.util!!! XXX |
8 |
|
9 |
import java.util.concurrent.*; // XXX This import goes away XXX |
10 |
import java.util.*; |
11 |
|
12 |
/** |
13 |
* A {@link Deque} that additionally supports operations that wait for |
14 |
* the deque to become non-empty when retrieving an element, and wait |
15 |
* for space to become available in the deque when storing an |
16 |
* element. These methods are summarized in the following table:<p> |
17 |
* |
18 |
* <table BORDER CELLPADDING=3 CELLSPACING=1> |
19 |
* <tr> |
20 |
* <td></td> |
21 |
* <td ALIGN=CENTER COLSPAN = 2> <b>First Element (Head)</b></td> |
22 |
* <td ALIGN=CENTER COLSPAN = 2> <b>Last Element (Tail)</b></td> |
23 |
* </tr> |
24 |
* <tr> |
25 |
* <td></td> |
26 |
* <td ALIGN=CENTER><em>Block</em></td> |
27 |
* <td ALIGN=CENTER><em>Time out</em></td> |
28 |
* <td ALIGN=CENTER><em>Block</em></td> |
29 |
* <td ALIGN=CENTER><em>Time out</em></td> |
30 |
* </tr> |
31 |
* <tr> |
32 |
* <td><b>Insert</b></td> |
33 |
* <td>{@link #putFirst putFirst(e)}</td> |
34 |
* <td>{@link #offerFirst(Object, long, TimeUnit) offerFirst(e, time, unit)}</td> |
35 |
* <td>{@link #putLast putLast(e)}</td> |
36 |
* <td>{@link #offerLast(Object, long, TimeUnit) offerLast(e, time, unit)}</td> |
37 |
* </tr> |
38 |
* <tr> |
39 |
* <td><b>Remove</b></td> |
40 |
* <td>{@link #takeFirst takeFirst()}</td> |
41 |
* <td>{@link #pollFirst(long, TimeUnit) pollFirst(time, unit)}</td> |
42 |
* <td>{@link #takeLast takeLast()}</td> |
43 |
* <td>{@link #pollLast(long, TimeUnit) pollLast(time, unit)}</td> |
44 |
* </tr> |
45 |
* </table> |
46 |
* |
47 |
* <p>Like any {@link BlockingQueue}, a {@code BlockingDeque} is |
48 |
* thread safe and may (or may not) be capacity-constrained. A |
49 |
* {@code BlockingDeque} implementation may be used directly as a |
50 |
* FIFO {@code BlockingQueue}. The blocking methods inherited from |
51 |
* the {@code BlockingQueue} interface are precisely equivalent to |
52 |
* {@code BlockingDeque} methods as indicated in the following table:<p> |
53 |
* |
54 |
* <table BORDER CELLPADDING=3 CELLSPACING=1> |
55 |
* <tr> |
56 |
* <td ALIGN=CENTER> <b>{@code BlockingQueue} Method</b></td> |
57 |
* <td ALIGN=CENTER> <b>Equivalent {@code BlockingDeque} Method</b></td> |
58 |
* </tr> |
59 |
* <tr> |
60 |
* <tr> |
61 |
* <td>{@link java.util.concurrent.BlockingQueue#put put(e)}</td> |
62 |
* <td>{@link #putLast putLast(e)}</td> |
63 |
* </tr> |
64 |
* <tr> |
65 |
* <td>{@link java.util.concurrent.BlockingQueue#take take()}</td> |
66 |
* <td>{@link #takeFirst takeFirst()}</td> |
67 |
* </tr> |
68 |
* <tr> |
69 |
* <td>{@link java.util.concurrent.BlockingQueue#offer(Object, long, TimeUnit) offer(e, time. unit)}</td> |
70 |
* <td>{@link #offerLast(Object, long, TimeUnit) offerLast(e, time, unit)}</td> |
71 |
* </tr> |
72 |
* <tr> |
73 |
* <td>{@link java.util.concurrent.BlockingQueue#poll(long, TimeUnit) poll(time, unit)}</td> |
74 |
* <td>{@link #pollFirst(long, TimeUnit) pollFirst(time, unit)}</td> |
75 |
* </tr> |
76 |
* </table> |
77 |
* |
78 |
* <p>This interface is a member of the |
79 |
* <a href="{@docRoot}/../guide/collections/index.html"> |
80 |
* Java Collections Framework</a>. |
81 |
* |
82 |
* @since 1.6 |
83 |
* @author Doug Lea |
84 |
* @param <E> the type of elements held in this collection |
85 |
*/ |
86 |
public interface BlockingDeque<E> extends Deque<E>, BlockingQueue<E> { |
87 |
|
88 |
/** |
89 |
* Adds the specified element as the first element of this deque, |
90 |
* waiting if necessary for space to become available. |
91 |
* @param o the element to add |
92 |
* @throws InterruptedException if interrupted while waiting |
93 |
* @throws NullPointerException if the specified element is {@code null} |
94 |
*/ |
95 |
void putFirst(E o) throws InterruptedException; |
96 |
|
97 |
/** |
98 |
* Adds the specified element as the last element of this deque, |
99 |
* waiting if necessary for space to become available. |
100 |
* @param o the element to add |
101 |
* @throws InterruptedException if interrupted while waiting |
102 |
* @throws NullPointerException if the specified element is {@code null} |
103 |
*/ |
104 |
void putLast(E o) throws InterruptedException; |
105 |
|
106 |
/** |
107 |
* Retrieves and removes the first element of this deque, waiting |
108 |
* if no elements are present on this deque. |
109 |
* @return the head of this deque |
110 |
* @throws InterruptedException if interrupted while waiting |
111 |
*/ |
112 |
E takeFirst() throws InterruptedException; |
113 |
|
114 |
/** |
115 |
* Retrieves and removes the last element of this deque, waiting |
116 |
* if no elements are present on this deque. |
117 |
* @return the head of this deque |
118 |
* @throws InterruptedException if interrupted while waiting |
119 |
*/ |
120 |
E takeLast() throws InterruptedException; |
121 |
|
122 |
/** |
123 |
* Inserts the specified element as the first element of this deque, |
124 |
* waiting if necessary up to the specified wait time for space to |
125 |
* become available. |
126 |
* @param o the element to add |
127 |
* @param timeout how long to wait before giving up, in units of |
128 |
* {@code unit} |
129 |
* @param unit a {@code TimeUnit} determining how to interpret the |
130 |
* {@code timeout} parameter |
131 |
* @return {@code true} if successful, or {@code false} if |
132 |
* the specified waiting time elapses before space is available |
133 |
* @throws InterruptedException if interrupted while waiting |
134 |
* @throws NullPointerException if the specified element is {@code null} |
135 |
*/ |
136 |
boolean offerFirst(E o, long timeout, TimeUnit unit) |
137 |
throws InterruptedException; |
138 |
|
139 |
/** |
140 |
* Inserts the specified element as the last element of this deque, |
141 |
* waiting if necessary up to the specified wait time for space to |
142 |
* become available. |
143 |
* @param o the element to add |
144 |
* @param timeout how long to wait before giving up, in units of |
145 |
* {@code unit} |
146 |
* @param unit a {@code TimeUnit} determining how to interpret the |
147 |
* {@code timeout} parameter |
148 |
* @return {@code true} if successful, or {@code false} if |
149 |
* the specified waiting time elapses before space is available |
150 |
* @throws InterruptedException if interrupted while waiting |
151 |
* @throws NullPointerException if the specified element is {@code null} |
152 |
*/ |
153 |
boolean offerLast(E o, long timeout, TimeUnit unit) |
154 |
throws InterruptedException; |
155 |
|
156 |
|
157 |
/** |
158 |
* Retrieves and removes the first element of this deque, waiting |
159 |
* if necessary up to the specified wait time if no elements are |
160 |
* present on this deque. |
161 |
* @param timeout how long to wait before giving up, in units of |
162 |
* {@code unit} |
163 |
* @param unit a {@code TimeUnit} determining how to interpret the |
164 |
* {@code timeout} parameter |
165 |
* @return the head of this deque, or {@code null} if the |
166 |
* specified waiting time elapses before an element is present |
167 |
* @throws InterruptedException if interrupted while waiting |
168 |
*/ |
169 |
E pollFirst(long timeout, TimeUnit unit) |
170 |
throws InterruptedException; |
171 |
|
172 |
/** |
173 |
* Retrieves and removes the last element of this deque, waiting |
174 |
* if necessary up to the specified wait time if no elements are |
175 |
* present on this deque. |
176 |
* @param timeout how long to wait before giving up, in units of |
177 |
* {@code unit} |
178 |
* @param unit a {@code TimeUnit} determining how to interpret the |
179 |
* {@code timeout} parameter |
180 |
* @return the head of this deque, or {@code null} if the |
181 |
* specified waiting time elapses before an element is present |
182 |
* @throws InterruptedException if interrupted while waiting |
183 |
*/ |
184 |
E pollLast(long timeout, TimeUnit unit) |
185 |
throws InterruptedException; |
186 |
|
187 |
/** |
188 |
* Adds the specified element as the last element of this deque, |
189 |
* waiting if necessary for space to become available. This |
190 |
* method is equivalent to putLast. |
191 |
* @param o the element to add |
192 |
* @throws InterruptedException if interrupted while waiting |
193 |
* @throws NullPointerException if the specified element is {@code null} |
194 |
*/ |
195 |
void put(E o) throws InterruptedException; |
196 |
|
197 |
/** |
198 |
* Inserts the specified element as the lest element of this |
199 |
* deque, if possible. When using deques that may impose |
200 |
* insertion restrictions (for example capacity bounds), method |
201 |
* {@code offer} is generally preferable to method {@link |
202 |
* Collection#add}, which can fail to insert an element only by |
203 |
* throwing an exception. This method is equivalent to |
204 |
* offerLast. |
205 |
* |
206 |
* @param o the element to add |
207 |
* @return {@code true} if it was possible to add the element to |
208 |
* this deque, else {@code false} |
209 |
* @throws NullPointerException if the specified element is {@code null} |
210 |
*/ |
211 |
boolean offer(E o, long timeout, TimeUnit unit) |
212 |
throws InterruptedException; |
213 |
|
214 |
/** |
215 |
* Retrieves and removes the first element of this deque, waiting |
216 |
* if no elements are present on this deque. |
217 |
* This method is equivalent to takeFirst. |
218 |
* @return the head of this deque |
219 |
* @throws InterruptedException if interrupted while waiting |
220 |
*/ |
221 |
E take() throws InterruptedException; |
222 |
|
223 |
/** |
224 |
* Retrieves and removes the first element of this deque, waiting |
225 |
* if necessary up to the specified wait time if no elements are |
226 |
* present on this deque. This method is equivalent to |
227 |
* pollFirst. |
228 |
* @param timeout how long to wait before giving up, in units of |
229 |
* {@code unit} |
230 |
* @param unit a {@code TimeUnit} determining how to interpret the |
231 |
* {@code timeout} parameter |
232 |
* @return the head of this deque, or {@code null} if the |
233 |
* specified waiting time elapses before an element is present |
234 |
* @throws InterruptedException if interrupted while waiting |
235 |
*/ |
236 |
E poll(long timeout, TimeUnit unit) |
237 |
throws InterruptedException; |
238 |
} |