1 | /** this class is fully thread-safe */ |
2 | class Flag {
|
3 | private boolean up; |
4 | private Trigger listeners = new Trigger(); |
5 | |
6 | /** returns true if flag was down before */ |
7 | public synchronized boolean raise() {
|
8 | boolean result = doRaise(); |
9 | if (result) {
|
10 | listeners.trigger(); |
11 | listeners = null; |
12 | } |
13 | return result; |
14 | } |
15 | |
16 | private synchronized boolean doRaise() {
|
17 | if (!up) {
|
18 | up = true; |
19 | notifyAll(); |
20 | return true; |
21 | } else |
22 | return false; |
23 | } |
24 | |
25 | public synchronized void waitUntilUp() {
|
26 | if (!up) {
|
27 | try {
|
28 | wait(); |
29 | } catch (InterruptedException e) {
|
30 | e.printStackTrace(); |
31 | } |
32 | } |
33 | } |
34 | |
35 | public void onRaise(Runnable listener) {
|
36 | if (!addListener(listener)) |
37 | listener.run(); |
38 | } |
39 | |
40 | private synchronized boolean addListener(Runnable listener) {
|
41 | if (!up) {
|
42 | listeners.addListener(listener); |
43 | return true; |
44 | } else |
45 | return false; |
46 | } |
47 | |
48 | public synchronized boolean isUp() {
|
49 | return up; |
50 | } |
51 | |
52 | public String toString() {
|
53 | return isUp() ? "up" : "down"; |
54 | } |
55 | |
56 | // currently does a semi-active wait with latency = 50 ms |
57 | public void waitForThisOr(Flag otherFlag) {
|
58 | while (!isUp() && !otherFlag.isUp()) |
59 | MultiCoreUtil.sleep(50); |
60 | } |
61 | } |
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| Snippet ID: | #1000781 |
| Snippet name: | Flag class with listeners (incomplete) |
| Eternal ID of this version: | #1000781/1 |
| Text MD5: | 83018195c822c1c7aec9305d168dc9b2 |
| Author: | stefan |
| Category: | |
| Type: | JavaX fragment (include) |
| Public (visible to everyone): | Yes |
| Archived (hidden from active list): | No |
| Created/modified: | 2015-08-27 01:57:30 |
| Source code size: | 1307 bytes / 61 lines |
| Pitched / IR pitched: | No / Yes |
| Views / Downloads: | 565 / 495 |
| Referenced in: | [show references] |