OnJava8-Examples/lowlevel/SynchronizedComparison.java at master · CSapprenticeWT/OnJava8-Examples · GitHub

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// lowlevel/SynchronizedComparison.java

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

// Synchronizing blocks instead of entire methods

// speeds up access.

import java.util.*;

import java.util.stream.*;

import java.util.concurrent.*;

import java.util.concurrent.atomic.*;

import onjava.Nap;

abstract class Guarded {

AtomicLong callCount = new AtomicLong();

public abstract void method();

@Override public String toString() {

return getClass().getSimpleName() +

": " + callCount.get();

}

class SynchronizedMethod extends Guarded {

@Override public synchronized void method() {

new Nap(0.01);

callCount.incrementAndGet();

}

class CriticalSection extends Guarded {

@Override public void method() {

new Nap(0.01);

synchronized(this) {

callCount.incrementAndGet();

}

class Caller implements Runnable {

private Guarded g;

Caller(Guarded g) { this.g = g; }

private AtomicLong successfulCalls =

new AtomicLong();

private AtomicBoolean stop =

new AtomicBoolean(false);

@Override public void run() {

new Timer().schedule(new TimerTask() {

public void run() { stop.set(true); }

}, 2500);

while(!stop.get()) {

g.method();

successfulCalls.getAndIncrement();

}

System.out.println(

"-> " + successfulCalls.get());

}

public class SynchronizedComparison {

static void test(Guarded g) {

List<CompletableFuture<Void>> callers =

Stream.of(

new Caller(g),

new Caller(g))

.map(CompletableFuture::runAsync)

.collect(Collectors.toList());

callers.forEach(CompletableFuture::join);

System.out.println(g);

}

public static void main(String[] args) {

test(new CriticalSection());

test(new SynchronizedMethod());

}

/* Output:

-> 159

CriticalSection: 636

-> 65

-> 21

-> 11

-> 68

SynchronizedMethod: 165

OnJava8-Examples/lowlevel/SynchronizedComparison.java at master · CSapprenticeWT/OnJava8-Examples · GitHub

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