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1 package suikwasha.distributedalgorithm.simulator;
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2
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3 import java.util.concurrent.CountDownLatch;
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4 import java.util.concurrent.atomic.AtomicLong;
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5
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6 public class Synchronizer
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7 {
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8 private AtomicLong counter;
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9 private CountDownLatch latch;
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10
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11 public Synchronizer()
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12 {
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13 counter = new AtomicLong();
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14 latch = new CountDownLatch(1);
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15 }
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16
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17 public long countup() throws IllegalStateException
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18 {
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19 // double checking , is it effective?
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20 if(latch.getCount() != 0){
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21 long value = counter.incrementAndGet();
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22 if(latch.getCount() != 0){
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23 return value;
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24 }
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25 }
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26
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27 throw new IllegalStateException("latch.getCount() == 0");
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28 }
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29
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30 public long countdown() throws IllegalStateException
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31 {
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32 long value = counter.decrementAndGet();
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33 if(value < 0){
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34 throw new IllegalStateException("counter < 0");
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35 }
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36
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37 if(value == 0){
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38 latch.countDown();
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39 }
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40
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41 return value;
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42 }
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43
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44 public void await() throws InterruptedException
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45 {
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46 latch.await();
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47 }
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48 }
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