Accidentally Returning Early
| ||||
| Copyright 1999 Sams Publishing |
| | ||
| | |
| Watching It Work with SureStopDemo |
| | |
| SureStopDemo (see Listing 16.3) starts several threads to demonstrate how SureStop works. But instead of SureStop , SureStopVerbose is used so that more detail about what is going on internally is printed. Although the threads running in SureStopDemo could have been stopped in a more orderly fashion by using interrupt() , they are not so that the functionality of SureStop can be fully exercised. SureStopDemo runs for about 25 seconds before automatically exiting the VM. |
| | |
| Listing 16.3 SureStopDemo.javaDemonstration Code for SureStopVerbose |
| | |
| 1: public class SureStopDemo extends Object { |
| 2: private static Thread launch( |
| 3: final String name , |
| 4: long lifeTime |
| 5: ) { |
| 6: |
| 7: final int loopCount = (int) (lifeTime / 1000); |
| 8: |
| 9: Runnable r = new Runnable() { |
| 10: public void run() { |
| 11: try { |
| 12: for (int i = 0; i < loopCount; i++) { |
| 13: Thread.sleep(1000); |
| 14: System.out.println( |
| 15: -> Running - + name); |
| 16: } |
| 17: } catch (InterruptedException x) { |
| 18: // ignore |
| 19: } |
| 20: } |
| 21: }; |
| 22: |
| 23: Thread t = new Thread(r); |
| 24: t.setName(name); |
| 25: t.start(); |
| 26: |
| 27: return t; |
| 28: } |
| 29: |
| 30: public static void main(String[] args) { |
| 31: Thread t0 = launch(T0, 1000); |
| 32: Thread t1 = launch(T1, 5000); |
| 33: Thread t2 = launch(T2, 15000); |
| 34: |
| 35: try { Thread.sleep(2000); } |
| 36: catch (InterruptedException x) { } |
| 37: |
| 38: SureStopVerbose.ensureStop(t0, 9000); |
| 39: SureStopVerbose.ensureStop(t1, 10000); |
| 40: SureStopVerbose.ensureStop(t2, 12000); |
| 41: |
| 42: try { Thread.sleep(20000); } |
| 43: catch (InterruptedException x) { } |
| 44: |
| 45: Thread t3 = launch(T3, 15000); |
| 46: SureStopVerbose.ensureStop(t3, 5000); |
| 47: |
| 48: try { Thread.sleep(1000); } |
| 49: catch (InterruptedException x) { } |
| 50: |
| 51: Thread t4 = launch(T4, 15000); |
| 52: SureStopVerbose.ensureStop(t4, 3000); |
| 53: } |
| 54: } |
| | |
| The launch() method (lines 228) is used to create a new thread and start it running. A name for the thread is passed in along with the amount of time that the thread should keep running before dying on its own. About once per second, the thread prints a message (lines 1216). z reference to the Thread created is returned (line 27). |
| | |
| The main() method launches three of these threads (lines 3133) and then sleeps for 2 seconds (lines 3536). It then specifies that SureStopVerbose should make certain that the threads are stopped (lines 3840). The main() method requests that t0 be stopped in 9 seconds, but t0 should have already died on its own about 1 second ago. It requests that t1 be stopped in 10 seconds, but t1 should stop on its own in about 3 more seconds. It requests that t2 be stopped in 12 seconds, and it will need to be stopped because t2 is scheduled to run for about 13 more seconds. The main thread then sleeps for 20 seconds to allow all this to play out (lines 4243). After this, two more threads are launched and monitored (lines 4552). |
| | |
| Listing 16.4 shows possible output when SureStopDemo is run. Your output should match closely, but some of the timing might be slightly different. |
| | |
| Listing 16.4 Possible Output from SureStopDemo |
| | |
| 1: -> Running - T0 |
| 2: -> Running - T1 |
| 3: -> Running - T2 |
| 4: -> Running - T1 |
| 5: -> Running - T2 |
| 6: main: SureStopVerbose instance created. |
| 7: SureStopThread: about to sleep for 0.5 seconds |
| 8: main: entering ensureStop() - name=T0, msGracePeriod=9000 |
| 9: main: already stopped, not added to list - T0 |
| 10: main: entering ensureStop() - name=T1, msGracePeriod=10000 |
| 11: main: added entry to pendingList, name=T1, stopTime=924307803230, in 9840 ms |
| 12: main: leaving ensureStop() - name=T1 |
| 13: main: entering ensureStop() - name=T2, msGracePeriod=12000 |
| 14: main: added entry to pendingList, name=T2, stopTime=924307805390, in 12000 ms |
| 15: main: leaving ensureStop() - name=T2 |
| 16: SureStopThread: done with sleep for 0.5 seconds |
| 17: SureStopThread: entering checkStopList() - stopList. size ()=0 |
| 18: SureStopThread: leaving checkStopList() - stopList.size()=0 |
| 19: SureStopThread: back from checkStopList(), sleepTime=9223371112546982037 |
| 20: SureStopThread: copying 2 elements from pendingList to stopList |
| 21: SureStopThread: pendingList.size()=0, stopList grew by 2 |
| 22: SureStopThread: about to sleep for 0.5 seconds |
| 23: -> Running - T1 |
| 24: -> Running - T2 |
| 25: SureStopThread: done with sleep for 0.5 seconds |
| 26: SureStopThread: entering checkStopList() - stopList.size()=2 |
| 27: SureStopThread: thread is alive - T1 |
| 28: SureStopThread: new minTime=924307803230 |
| 29: SureStopThread: thread is alive - T2 |
| 30: SureStopThread: new minTime=924307803230 |
| 31: SureStopThread: leaving checkStopList() - stopList.size()=2 |
| 32: SureStopThread: back from checkStopList(), sleepTime=8960 |
| 33: SureStopThread: about to wait on pendingList for 8960 ms |
| 34: -> Running - T1 |
| 35: -> Running - T2 |
| 36: -> Running - T1 |
| 37: -> Running - T2 |
| 38: -> Running - T2 |
| 39: -> Running - T2 |
| 40: -> Running - T2 |
| 41: -> Running - T2 |
| 42: -> Running - T2 |
| 43: -> Running - T2 |
| 44: -> Running - T2 |
| 45: SureStopThread: waited on pendingList for 8960 ms |
| 46: SureStopThread: about to sleep for 0.5 seconds |
| 47: SureStopThread: done with sleep for 0.5 seconds |
| 48: SureStopThread: entering checkStopList() - stopList.size()=2 |
| 49: SureStopThread: thread died on its own - T1 |
| 50: SureStopThread: thread is alive - T2 |
| 51: SureStopThread: new minTime=924307805390 |
| 52: SureStopThread: leaving checkStopList() - stopList.size()=1 |
| 53: SureStopThread: back from checkStopList(), sleepTime=1620 |
| 54: SureStopThread: about to wait on pendingList for 1620 ms |
| 55: -> Running - T2 |
| 56: -> Running - T2 |
| 57: SureStopThread: waited on pendingList for 1650 ms |
| 58: SureStopThread: about to sleep for 0.5 seconds |
| 59: SureStopThread: done with sleep for 0.5 seconds |
| 60: SureStopThread: entering checkStopList() - stopList.size()=1 |
| 61: SureStopThread: thread is alive - T2 |
| 62: SureStopThread: timed out, stopping - T2 |
| 63: SureStopThread: leaving checkStopList() - stopList.size()=0 |
| 64: SureStopThread: back from checkStopList(), sleepTime=9223371112546969897 |
| 65: SureStopThread: about to wait on pendingList for 9223371112546969897 ms |
| 66: main: entering ensureStop() - name=T3, msGracePeriod=5000 |
| 67: main: added entry to pendingList, name=T3, stopTime=924307818440, in 5000 ms |
| 68: SureStopThread: waited on pendingList for 7530 ms |
| 69: SureStopThread: copying 1 elements from pendingList to stopList |
| 70: SureStopThread: pendingList.size()=0, stopList grew by 1 |
| 71: SureStopThread: about to sleep for 0.5 seconds |
| 72: main: leaving ensureStop() - name=T3 |
| 73: SureStopThread: done with sleep for 0.5 seconds |
| 74: SureStopThread: entering checkStopList() - stopList.size()=1 |
| 75: SureStopThread: thread is alive - T3 |
| 76: SureStopThread: new minTime=924307818440 |
| 77: SureStopThread: leaving checkStopList() - stopList.size()=1 |
| 78: SureStopThread: back from checkStopList(), sleepTime=4510 |
| 79: SureStopThread: about to wait on pendingList for 4510 ms |
| 80: main: entering ensureStop() - name=T4, msGracePeriod=3000 |
| 81: main: added entry to pendingList, name=T4, stopTime=924307817430, in 3000 ms |
| 82: SureStopThread: waited on pendingList for 500 ms |
| 83: SureStopThread: copying 1 elements from pendingList to stopList |
| 84: SureStopThread: pendingList.size()=0, stopList grew by 1 |
| 85: SureStopThread: about to sleep for 0.5 seconds |
| 86: main: leaving ensureStop() - name=T4 |
| 87: -> Running - T3 |
| 88: SureStopThread: done with sleep for 0.5 seconds |
| 89: SureStopThread: entering checkStopList() - stopList.size()=2 |
| 90: SureStopThread: thread is alive - T3 |
| 91: SureStopThread: new minTime=924307818440 |
| 92: SureStopThread: thread is alive - T4 |
| 93: SureStopThread: new minTime=924307817430 |
| 94: SureStopThread: leaving checkStopList() - stopList.size()=2 |
| 95: SureStopThread: back from checkStopList(), sleepTime=2510 |
| 96: SureStopThread: about to wait on pendingList for 2510 ms |
| 97: -> Running - T4 |
| 98: -> Running - T3 |
| 99: -> Running - T4 |
| 100: -> Running - T3 |
| 101: -> Running - T4 |
| 102: -> Running - T3 |
| 103: SureStopThread: waited on pendingList for 2530 ms |
| 104: SureStopThread: about to sleep for 0.5 seconds |
| 105: SureStopThread: done with sleep for 0.5 seconds |
| 106: SureStopThread: entering checkStopList() - stopList.size()=2 |
| 107: SureStopThread: thread is alive - T3 |
| 108: SureStopThread: new minTime=924307818440 |
| 109: SureStopThread: thread is alive - T4 |
| 110: SureStopThread: timed out, stopping - T4 |
| 111: SureStopThread: leaving checkStopList() - stopList.size()=1 |
| 112: SureStopThread: back from checkStopList(), sleepTime=500 |
| 113: SureStopThread: about to wait on pendingList for 500 ms |
| 114: -> Running - T3 |
| 115: SureStopThread: waited on pendingList for 500 ms |
| 116: SureStopThread: about to sleep for 0.5 seconds |
| 117: SureStopThread: done with sleep for 0.5 seconds |
| 118: SureStopThread: entering checkStopList() - stopList.size()=1 |
| 119: SureStopThread: thread is alive - T3 |
| 120: SureStopThread: timed out, stopping - T3 |
| 121: SureStopThread: leaving checkStopList() - stopList.size()=0 |
| 122: SureStopThread: back from checkStopList(), sleepTime=9223371112546956877 |
| 123: SureStopThread: about to wait on pendingList for 9223371112546956877 ms |
| | |
| Notice that as predicted , t0 stopped on its own before being monitored by SureStopVerbose (line 9). Monitoring began on t1 (lines 11, 27), but the thread died on its own before timing out (line 49). Similarly, monitoring began on t2 (lines 14, 29, 50, 61), and the thread timed out and was stopped by SureStopVerbose (line 62). |
| |  | ||
| Toc | |||
