90 lines
2.0 KiB
Java
90 lines
2.0 KiB
Java
// lowlevel/SynchronizedComparison.java
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// (c)2017 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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// Synchronizing blocks instead of entire methods
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// speeds up access.
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import java.util.*;
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import java.util.stream.*;
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import java.util.concurrent.*;
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import java.util.concurrent.atomic.*;
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import onjava.Nap;
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abstract class Guarded {
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AtomicLong callCount = new AtomicLong();
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public abstract void method();
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@Override
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public String toString() {
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return getClass().getSimpleName() +
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": " + callCount.get();
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}
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}
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class SynchronizedMethod extends Guarded {
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public synchronized void method() {
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new Nap(0.01);
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callCount.incrementAndGet();
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}
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}
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class CriticalSection extends Guarded {
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public void method() {
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new Nap(0.01);
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synchronized(this) {
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callCount.incrementAndGet();
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}
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}
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}
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class Caller implements Runnable {
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private Guarded g;
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Caller(Guarded g) { this.g = g; }
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private AtomicLong successfulCalls =
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new AtomicLong();
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private AtomicBoolean stop =
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new AtomicBoolean(false);
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@Override
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public void run() {
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new Timer().schedule(new TimerTask() {
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public void run() { stop.set(true); }
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}, 2500);
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while(!stop.get()) {
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g.method();
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successfulCalls.getAndIncrement();
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}
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System.out.println(
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"-> " + successfulCalls.get());
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}
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}
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public class SynchronizedComparison {
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static void test(Guarded g) {
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List<CompletableFuture<Void>> callers =
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Stream.of(
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new Caller(g),
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new Caller(g),
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new Caller(g),
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new Caller(g))
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.map(CompletableFuture::runAsync)
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.collect(Collectors.toList());
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callers.forEach(CompletableFuture::join);
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System.out.println(g);
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}
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public static void main(String[] args) {
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test(new CriticalSection());
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test(new SynchronizedMethod());
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}
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}
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/* Output:
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-> 243
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-> 243
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-> 243
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-> 243
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CriticalSection: 972
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-> 69
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-> 61
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-> 83
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-> 36
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SynchronizedMethod: 249
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*/
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