Last change
on this file since 222 was 2, checked in by Rick van der Zwet, 15 years ago |
Initial import of data of old repository ('data') worth keeping (e.g. tracking
means of URL access statistics)
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File size:
1.4 KB
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[2] | 1 | /*
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| 2 | * Rick van der Zwet
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| 3 | * 0433373
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| 4 | * Java programming assigment 1.2
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| 5 | * Licence: BSD
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| 6 | * $Id: Database.java 270 2007-10-13 13:45:29Z rick $
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| 7 | */
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| 8 |
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| 9 | class Database
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| 10 | {
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| 11 | // Read lock, call next person
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| 12 | // Write lock, call next person when done
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| 13 | private int readlock = 0;
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| 14 | private boolean writelock = false;
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| 15 | private boolean writerequest = false;
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| 16 |
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| 17 | private String value = new String("INIT");
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| 18 |
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| 19 | Database () {}; // constructor
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| 20 |
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| 21 | synchronized void get_readlock ()
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| 22 | {
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| 23 | while (writelock || writerequest)
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| 24 | {
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| 25 | try { wait(); } catch (InterruptedException e)
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| 26 | {
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| 27 | System.out.println("interruptedException caught");
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| 28 | }
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| 29 | }
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| 30 | readlock++;
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| 31 | }
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| 32 |
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| 33 | synchronized String read ()
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| 34 | {
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| 35 | return (value);
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| 36 | }
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| 37 |
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| 38 | synchronized void release_readlock ()
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| 39 | {
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| 40 | readlock--;
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| 41 | notify();
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| 42 | }
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| 43 |
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| 44 | synchronized void get_writelock()
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| 45 | {
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| 46 | writerequest = true;
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| 47 | while (writelock && readlock > 0)
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| 48 | {
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| 49 | try { wait(); } catch (InterruptedException e)
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| 50 | {
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| 51 | System.out.println("interruptedException caught");
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| 52 | }
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| 53 | }
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| 54 | writelock = true;
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| 55 | writerequest = false;
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| 56 | }
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| 57 |
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| 58 | synchronized void write (String text)
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| 59 | {
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| 60 | value = value + ":" + text;
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| 61 | }
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| 62 |
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| 63 | synchronized void release_writelock()
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| 64 | {
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| 65 | writelock = false;
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| 66 | notify();
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| 67 | }
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| 68 | }
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| 69 |
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