2018-09-26.jpg
今天主要记录下两个比较有意思的应用实例
1 吐司BlockingQueue
一台机器具有三个任务,一个是制作吐司、一个给吐司涂抹黄油、另一个在摸过黄油的吐司上涂抹果酱。我们可以通过各个处理过程之间的blockingQueue来运行这个吐司制作程序。
//: concurrency/ToastOMatic.java
// A toaster that uses queues.
package com.lhsjohn.comcurrency.prac;
import java.util.concurrent.*;
import java.util.*;
class Toast {
public enum Status {
DRY, BUTTERED, JAMMED
}
private Status status = Status.DRY;
private final int id;
public Toast(int idn) {
id = idn;
}
public void butter() {
status = Status.BUTTERED;
}
public void jam() {
status = Status.JAMMED;
}
public Status getStatus() {
return status;
}
public int getId() {
return id;
}
public String toString() {
return "Toast " + id + ": " + status;
}
}
class ToastQueue extends LinkedBlockingQueue<Toast> {
}
class Toaster implements Runnable {
private ToastQueue toastQueue;
private int count = 0;
private Random rand = new Random(47);
public Toaster(ToastQueue tq) {
toastQueue = tq;
}
public void run() {
try {
while (!Thread.interrupted()) {
TimeUnit.MILLISECONDS.sleep(100 + rand.nextInt(500));
// Make toast
Toast t = new Toast(count++);
System.out.println(t);
// Insert into queue
toastQueue.put(t);
}
} catch (InterruptedException e) {
System.out.println("Toaster interrupted");
}
System.out.println("Toaster off");
}
}
// Apply butter to toast:
class Butterer implements Runnable {
private ToastQueue dryQueue, butteredQueue;
public Butterer(ToastQueue dry, ToastQueue buttered) {
dryQueue = dry;
butteredQueue = buttered;
}
public void run() {
try {
while (!Thread.interrupted()) {
// Blocks until next piece of toast is available:
Toast t = dryQueue.take();
t.butter();
System.out.println(t);
butteredQueue.put(t);
}
} catch (InterruptedException e) {
System.out.println("Butterer interrupted");
}
System.out.println("Butterer off");
}
}
// Apply jam to buttered toast:
class Jammer implements Runnable {
private ToastQueue butteredQueue, finishedQueue;
public Jammer(ToastQueue buttered, ToastQueue finished) {
butteredQueue = buttered;
finishedQueue = finished;
}
public void run() {
try {
while (!Thread.interrupted()) {
// Blocks until next piece of toast is available:
Toast t = butteredQueue.take();
t.jam();
System.out.println(t);
finishedQueue.put(t);
}
} catch (InterruptedException e) {
System.out.println("Jammer interrupted");
}
System.out.println("Jammer off");
}
}
// Consume the toast:
class Eater implements Runnable {
private ToastQueue finishedQueue;
private int counter = 0;
public Eater(ToastQueue finished) {
finishedQueue = finished;
}
public void run() {
try {
while (!Thread.interrupted()) {
// Blocks until next piece of toast is available:
Toast t = finishedQueue.take();
// Verify that the toast is coming in order,
// and that all pieces are getting jammed:
if (t.getId() != counter++ || t.getStatus() != Toast.Status.JAMMED) {
System.out.println(">>>> Error: " + t);
System.exit(1);
} else
System.out.println("Chomp! " + t);
}
} catch (InterruptedException e) {
System.out.println("Eater interrupted");
}
System.out.println("Eater off");
}
}
public class ToastOMatic {
public static void main(String[] args) throws Exception {
ToastQueue dryQueue = new ToastQueue(), butteredQueue = new ToastQueue(), finishedQueue = new ToastQueue();
ExecutorService exec = Executors.newCachedThreadPool();
exec.execute(new Toaster(dryQueue));
exec.execute(new Butterer(dryQueue, butteredQueue));
exec.execute(new Jammer(butteredQueue, finishedQueue));
exec.execute(new Eater(finishedQueue));
TimeUnit.SECONDS.sleep(5);
exec.shutdownNow();
}
} /* (Execute to see output) */// :~
运行结果：
Toast 1: DRY
Toast 2: DRY
Toast 3: DRY
Toast 4: DRY
Toast 5: DRY
Toast 6: DRY
Toast 7: DRY
Toast 8: DRY
Toast 9: DRY
Toast 10: DRY
Toast 11: DRY
Toast 12: DRY
Eater interrupted
Eater off
Toaster interrupted
Toaster off
Jammer interrupted
Jammer off
2.仿真之赛马
package com.lhsjohn.comcurrency.prac;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
class Horse implements Runnable {
private static int counter = 0;
private final int id = counter++;
private int strides = 0;
private static Random rand = new Random(47);
private static CyclicBarrier barrier;
public Horse(CyclicBarrier b) { barrier = b; }
public synchronized int getStrides() { return strides; }
public void run() {
try {
while(!Thread.interrupted()) {
synchronized(this) {
strides += rand.nextInt(3); // Produces 0, 1 or 2
}
barrier.await();
}
} catch(InterruptedException e) {
// A legitimate way to exit
} catch(BrokenBarrierException e) {
// This one we want to know about
throw new RuntimeException(e);
}
}
public String toString() { return "Horse " + id + " "; }
public String tracks() {
StringBuilder s = new StringBuilder();
for(int i = 0; i < getStrides(); i++)
s.append("*");
s.append(id);
return s.toString();
}
}
public class HorseRace {
static final int FINISH_LINE = 75;
private List<Horse> horses = new ArrayList<Horse>();
private ExecutorService exec =
Executors.newCachedThreadPool();
private CyclicBarrier barrier;
public HorseRace(int nHorses, final int pause) {
barrier = new CyclicBarrier(nHorses, new Runnable() {
public void run() {
StringBuilder s = new StringBuilder();
for(int i = 0; i < FINISH_LINE; i++)
s.append("="); // The fence on the racetrack
System.out.println(s);
for(Horse horse : horses)
System.out.println(horse.tracks());
for(Horse horse : horses)
if(horse.getStrides() >= FINISH_LINE) {
System.out.println(horse + "won!");
exec.shutdownNow();
return;
}
try {
TimeUnit.MILLISECONDS.sleep(pause);
} catch(InterruptedException e) {
System.out.println("barrier-action sleep interrupted");
}
}
});
for(int i = 0; i < nHorses; i++) {
Horse horse = new Horse(barrier);
horses.add(horse);
exec.execute(horse);
}
}
public static void main(String[] args) {
int nHorses = 5;
int pause = 200;
if(args.length > 0) { // Optional argument
int n = new Integer(args[0]);
nHorses = n > 0 ? n : nHorses;
}
if(args.length > 1) { // Optional argument
int p = new Integer(args[1]);
pause = p > -1 ? p : pause;
}
new HorseRace(nHorses, pause);
}
} /* (Execute to see output) *///:~
运行结果： 看成是动态的👀
************************************************************************1
*************************************************************************2
**************************************************3
******************************************4
===========================================================================
***************************************************0
**************************************************************************1
*************************************************************************2
****************************************************3
******************************************4
===========================================================================
***************************************************0
****************************************************************************1
*************************************************************************2
******************************************************3
*******************************************4
Horse 1 won!
作者:lhsjohn
网友评论