104 lines
2.9 KiB
Java
104 lines
2.9 KiB
Java
//: concurrency/OrnamentalGarden.java
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// ©2015 MindView LLC: see Copyright.txt
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import java.util.concurrent.*;
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import java.util.*;
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import static com.mindviewinc.util.Print.*;
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class Count {
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private int count = 0;
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private Random rand = new Random(47);
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// Remove the synchronized keyword to see counting fail:
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public synchronized int increment() {
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int temp = count;
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if(rand.nextBoolean()) // Yield half the time
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Thread.yield();
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return (count = ++temp);
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}
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public synchronized int value() { return count; }
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}
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class Entrance implements Runnable {
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private static Count count = new Count();
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private static List<Entrance> entrances =
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new ArrayList<>();
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private int number = 0;
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// Doesn't need synchronization to read:
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private final int id;
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private static volatile boolean canceled = false;
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// Atomic operation on a volatile field:
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public static void cancel() { canceled = true; }
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public Entrance(int id) {
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this.id = id;
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// Keep this task in a list. Also prevents
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// garbage collection of dead tasks:
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entrances.add(this);
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}
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@Override
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public void run() {
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while(!canceled) {
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synchronized(this) {
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++number;
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}
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print(this + " Total: " + count.increment());
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try {
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TimeUnit.MILLISECONDS.sleep(100);
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} catch(InterruptedException e) {
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print("sleep interrupted");
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}
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}
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print("Stopping " + this);
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}
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public synchronized int getValue() { return number; }
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@Override
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public String toString() {
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return "Entrance " + id + ": " + getValue();
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}
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public static int getTotalCount() {
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return count.value();
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}
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public static int sumEntrances() {
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int sum = 0;
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for(Entrance entrance : entrances)
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sum += entrance.getValue();
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return sum;
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}
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}
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public class OrnamentalGarden {
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public static void main(String[] args) throws Exception {
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ExecutorService exec = Executors.newCachedThreadPool();
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for(int i = 0; i < 5; i++)
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exec.execute(new Entrance(i));
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// Run for a while, then stop and collect the data:
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TimeUnit.SECONDS.sleep(3);
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Entrance.cancel();
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exec.shutdown();
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if(!exec.awaitTermination(250, TimeUnit.MILLISECONDS))
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print("Some tasks were not terminated!");
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print("Total: " + Entrance.getTotalCount());
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print("Sum of Entrances: " + Entrance.sumEntrances());
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}
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} /* Output: (First and last 10 Lines)
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Entrance 0: 1 Total: 1
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Entrance 1: 1 Total: 2
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Entrance 4: 1 Total: 5
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Entrance 3: 1 Total: 3
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Entrance 2: 1 Total: 4
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Entrance 0: 2 Total: 6
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Entrance 1: 2 Total: 7
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Entrance 4: 2 Total: 8
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Entrance 2: 2 Total: 10
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Entrance 3: 2 Total: 9
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________...________...________...________...________
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Entrance 4: 30 Total: 147
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Entrance 2: 30 Total: 149
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Entrance 3: 30 Total: 150
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Stopping Entrance 0: 30
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Stopping Entrance 1: 30
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Stopping Entrance 4: 30
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Stopping Entrance 2: 30
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Stopping Entrance 3: 30
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Total: 150
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Sum of Entrances: 150
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*///:~
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