68 lines
1.9 KiB
Java
68 lines
1.9 KiB
Java
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//: concurrency/SemaphoreDemo.java
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// Testing the Pool class
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import java.util.concurrent.*;
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import java.util.*;
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import static net.mindview.util.Print.*;
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// A task to check a resource out of a pool:
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class CheckoutTask<T> implements Runnable {
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private static int counter = 0;
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private final int id = counter++;
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private Pool<T> pool;
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public CheckoutTask(Pool<T> pool) {
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this.pool = pool;
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}
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public void run() {
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try {
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T item = pool.checkOut();
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print(this + "checked out " + item);
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TimeUnit.SECONDS.sleep(1);
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print(this +"checking in " + item);
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pool.checkIn(item);
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} catch(InterruptedException e) {
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// Acceptable way to terminate
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}
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}
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public String toString() {
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return "CheckoutTask " + id + " ";
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}
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}
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public class SemaphoreDemo {
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final static int SIZE = 25;
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public static void main(String[] args) throws Exception {
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final Pool<Fat> pool =
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new Pool<Fat>(Fat.class, SIZE);
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ExecutorService exec = Executors.newCachedThreadPool();
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for(int i = 0; i < SIZE; i++)
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exec.execute(new CheckoutTask<Fat>(pool));
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print("All CheckoutTasks created");
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List<Fat> list = new ArrayList<Fat>();
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for(int i = 0; i < SIZE; i++) {
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Fat f = pool.checkOut();
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printnb(i + ": main() thread checked out ");
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f.operation();
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list.add(f);
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}
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Future<?> blocked = exec.submit(new Runnable() {
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public void run() {
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try {
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// Semaphore prevents additional checkout,
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// so call is blocked:
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pool.checkOut();
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} catch(InterruptedException e) {
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print("checkOut() Interrupted");
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}
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}
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});
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TimeUnit.SECONDS.sleep(2);
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blocked.cancel(true); // Break out of blocked call
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print("Checking in objects in " + list);
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for(Fat f : list)
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pool.checkIn(f);
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for(Fat f : list)
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pool.checkIn(f); // Second checkIn ignored
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exec.shutdown();
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}
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} /* (Execute to see output) *///:~
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