这是我想要做的。我有许多线程应该在它们继续之前等待共同点，所以显而易见的解决方案是使用CyclicBarrier。但我还想计算线程执行所花费的总时间。我在类ConcurrentExecutionActionTimer中定义了以下实用程序方法。
public static long elapsedTimeUsingCyclicBarrier(Executor executor, int concurrency, final Runnable action) throws InterruptedException
{
final Runnable barrierAction = new Runnable() {
@Override
public void run() {
System.out.println("Condition of barrier is met.");
}
};
final
CyclicBarrier barrier = new CyclicBarrier(concurrency, barrierAction);
final CountDownLatch done = new CountDownLatch(concurrency);
for(int i=0; i<concurrency; i++ ){
executor.execute(new Runnable() {
@Override
public void run() {
try {
System.out.println("Waiting at barrier.");
barrier.await();
action.run();
//Cyclic barrier gets reset automatically. Again wait for them to finish.
barrier.await();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
} catch (BrokenBarrierException e) {
e.printStackTrace();
} finally {
done.countDown();
}
}
});
}
long startNanoTime = System.nanoTime();
done.await();
return System.nanoTime() - startNanoTime;
}
然后我把它称为：
public static void main(String[] args) {
//Executor is replacement for common thread idiom: (new Thread(r)).start() to e.execute(r)
ExecutorService executor = Executors.newFixedThreadPool(10);
Worker action = new Worker();
int concurrency = 5;
try {
long elapsedTime = ConcurrentExecutionActionTimer.elapsedTimeUsingCyclicBarrier(executor, concurrency, action);
double seconds = (double)elapsedTime / 1000000000.0;
System.out.println("Time Taken approximately: " + seconds + "seconds.");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
这里Worker假设我的线程做了一些工作。例如：
class Worker implements Runnable {
@Override
public void run() {
System.out.println("Doing work.");
for(int i=0; i<20; i++) {
try {
Thread.sleep(500);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
System.out.println("Finished.");
}
}
由于我想打印所花费的时间，我必须使用CountDownLatch来确保控件在所有线程完成之前不会返回到main。我们还有其他方法可以确保相同的功能吗？
答案 0 :(得分：1)
您应该使用相同的CyclicBarrier实例。唯一的区别是你使循环障碍计数为#threads + 1.然后你可以使用该障碍来计算完成所有线程所花费的时间。当达到第一个屏障时计算开始时间，并且当达到第二个屏障时计算结束时间。通过这种方式，您可以大致了解所有线程何时启动以及所有线程何时完成。
因此：
long startNanoTime = System.nanoTime();
done.await();
return System.nanoTime() - startNanoTime;
变为：
barrier.await()
long startNanoTime = System.nanoTime();
barrier.await();
return System.nanoTime() - startNanoTime;
答案 1 :(得分：0)
import java.io.*;
导入java.util。*; 导入java.util.concurrent.CyclicBarrier;
类BusLine {
private String destination;
protected static int max_seat, checkpoint;
private ArrayList<Bus> BUSA = new ArrayList<Bus>();
private ArrayList<Bus> BUSC = new ArrayList<Bus>();
private ArrayList<Group> GROUP_A = new ArrayList<Group>();
private ArrayList<Group> GROUP_C = new ArrayList<Group>();
public BusLine(int ms, int cp, String d) {
max_seat = ms;
checkpoint = cp;
destination = d;
}
public String getDestination() {
return destination;
}
public void printAirportCheckpoint() {
System.out.println();
System.out.printf("%s >> %d airport-bound buses have been allocated.", Thread.currentThread().getName(), BUSA.size());
}
public void printCityCheckpoint() {
System.out.println();
System.out.printf("%s >> %d city-bound buses have been allocated.", Thread.currentThread().getName(), BUSC.size());
System.out.println();
System.out.println();
}
public void BusBoundA() {
int temp = 0;
for (int i = 0; i < BUSA.size(); i++) {
if (BUSA.get(i).getName().equals("A" + i)) {
temp++;
}
}
System.out.println();
System.out.printf("%s >> ==== Airport Bound ====", Thread.currentThread().getName());
System.out.println();
for (int i = 0; i < temp; i++) {
System.out.printf("%s >> %s : ", Thread.currentThread().getName(), "A" + i);
for (int j = 0; j < GROUP_A.size(); j++) {
if (GROUP_A.get(j).getBusname().equals("A" + i)) {
System.out.printf(" %-20s(%2d seats)", GROUP_A.get(j).getName(), GROUP_A.get(j).getSeat());
//System.out.printf(",");
}
} System.out.println();
}
}
public void BusBoundC() {
int temp = 0;
for (int i = 0; i < BUSC.size(); i++) {
if (BUSC.get(i).getName().equals("C" + i)) {
temp++;
}
}
System.out.println();
System.out.printf("%s >> ==== City Bound ====", Thread.currentThread().getName());
System.out.println();
for (int i = 0; i < temp; i++) {
System.out.printf("%s >> %s : ", Thread.currentThread().getName(), "C" + i);
for (int j = 0; j < GROUP_C.size(); j++) {
if (GROUP_C.get(j).getBusname().equals("C" + i)) {
System.out.printf(" %-20s(%2d seats)", GROUP_C.get(j).getName(), GROUP_C.get(j).getSeat());
//System.out.printf(",");
}
} System.out.println();
}
}
synchronized public void allocateBus(Data d) {
TicketCounter T = (TicketCounter) (Thread.currentThread());
while (d.getSeat() != 0) {
if ("A".equals(d.getDestination())) {
if (BUSA.size() == 0 || BUSA.get(BUSA.size() - 1).getAvailableSeat() == 0) {
BUSA.add(new Bus("A" + BUSA.size()));
}
if (d.getSeat() <= BUSA.get(BUSA.size() - 1).getAvailableSeat()) {
System.out.printf("%s >> Transaction %2d : %-20s(%2d seats) bus %s\n", T.getName(), d.getTransaction(), d.getName(), d.getSeat(), BUSA.get(BUSA.size() - 1).getName());
GROUP_A.add(new Group(BUSA.get(BUSA.size() - 1).getName(), d.getName(), d.getSeat()));
BUSA.get(BUSA.size() - 1).Bookingseat(d.getSeat());
d.finishedBooking(d.getSeat());
} else {
System.out.printf("%s >> Transaction %2d : %-20s(%2d seats) bus %s\n", T.getName(), d.getTransaction(), d.getName(), BUSA.get(BUSA.size() - 1).getAvailableSeat(), BUSA.get(BUSA.size() - 1).getName());
GROUP_A.add(new Group(BUSA.get(BUSA.size() - 1).getName(), d.getName(), BUSA.get(BUSA.size() - 1).getAvailableSeat()));
d.finishedBooking(BUSA.get(BUSA.size() - 1).getAvailableSeat());
BUSA.get(BUSA.size() - 1).Bookingseat(BUSA.get(BUSA.size() - 1).getAvailableSeat());
}
} else {
if (BUSC.size() == 0 || BUSC.get(BUSC.size() - 1).getAvailableSeat() == 0) {
BUSC.add(new Bus("C" + BUSC.size()));
}
if (d.getSeat() <= BUSC.get(BUSC.size() - 1).getAvailableSeat()) {
System.out.printf("%s >> Transaction %2d : %-20s(%2d seats) bus %s\n", T.getName(), d.getTransaction(), d.getName(), d.getSeat(), BUSC.get(BUSC.size() - 1).getName());
GROUP_C.add(new Group(BUSC.get(BUSC.size() - 1).getName(), d.getName(), d.getSeat()));
BUSC.get(BUSC.size() - 1).Bookingseat(d.getSeat());
d.finishedBooking(d.getSeat());
} else {
System.out.printf("%s >> Transaction %2d : %-20s(%2d seats) bus %s\n", T.getName(), d.getTransaction(), d.getName(), BUSC.get(BUSC.size() - 1).getAvailableSeat(), BUSC.get(BUSC.size() - 1).getName());
GROUP_C.add(new Group(BUSC.get(BUSC.size() - 1).getName(), d.getName(), BUSC.get(BUSC.size() - 1).getAvailableSeat()));
d.finishedBooking(BUSC.get(BUSC.size() - 1).getAvailableSeat());
BUSC.get(BUSC.size() - 1).Bookingseat(BUSC.get(BUSC.size() - 1).getAvailableSeat());
}
}
}
}
}
班组{
private String busname, name;
private int seat;
public Group(String n, String b, int s) {
busname = n;
name = b;
seat = s;
}
public String getName() { return name; }
public String getBusname() { return busname; }
public int getSeat() { return seat; }
}
类巴士{
private String Busname, group_name;
private int availableseat, seat;
public int getAvailableSeat() { return availableseat; }
public String getName() { return Busname; }
public void Bookingseat(int s) { availableseat -= s; }
public String getGroupname() { return group_name; }
public Bus(String n) {
availableseat = BusLine.max_seat;
Busname = n;
}
public Bus(String n, int s) {
group_name = n;
seat = s;
}
public Bus(String n, String gn, int s) {
Busname = n;
group_name = gn;
availableseat = s;
}
}
类数据{
private String name, destination;
private int seat, transaction, count = 0;
public int getCount() { return count; }
public int getTransaction() { return transaction; }
public String getName() { return name; }
public int getSeat() { return seat; }
public String getDestination() { return destination; }
public void finishedBooking(int s) { seat -= s; }
public Data(int t, String n, int s, String d) {
transaction = t;
name = n;
seat = s;
destination = d;
}
}
TicketCounter类扩展了线程{
ArrayList<Data> transaction;
BusLine Airport, City;
private CyclicBarrier cfinish;
public void setCyclicBarrier(CyclicBarrier f) {
cfinish = f;
}
public TicketCounter(String n, ArrayList<Data> d, BusLine a, BusLine c) {
super(n);
transaction = d;
Airport = a;
City = c;
}
public void run() {
for (int i = 0; i < transaction.size(); i++) {
if (transaction.get(i).getTransaction() == BusLine.checkpoint) {
try {
cfinish.await();
cfinish.await();
} catch (Exception e) {}
}
if ("A".equals(transaction.get(i).getDestination())) {
Airport.allocateBus(transaction.get(i));
} else {
City.allocateBus(transaction.get(i));
}
}
}
}
class Userinput {
private ArrayList<Data> DATA1 = new ArrayList<Data>();
private ArrayList<Data> DATA2 = new ArrayList<Data>();
private ArrayList<Data> DATA3 = new ArrayList<Data>();
public Userinput() {}
public ArrayList<Data> getDATA1() { return DATA1; }
public ArrayList<Data> getDATA2() { return DATA2; }
public ArrayList<Data> getDATA3() { return DATA3; }
public void input() {
String infile[] = {"T1.txt", "T2.txt", "T3.txt"};
for (int i = 0; i < 3; i++) {
boolean opensuccess = false;
while (!opensuccess) {
try ( Scanner scanfile = new Scanner(new File(infile[i]));) {
while (scanfile.hasNext()) {
opensuccess = true;
String line = scanfile.nextLine();
String[] buf = line.split(",");
int transaction = Integer.parseInt(buf[0].trim());
String name = buf[1].trim();
int seat = Integer.parseInt(buf[2].trim());
String destination = buf[3].trim();
Data d = new Data(transaction, name, seat, destination);
switch (i) {
case 0: DATA1.add(d);
break;
case 1: DATA2.add(d);
break;
case 2: DATA3.add(d);
break;
}
}
} catch (FileNotFoundException e) {
System.out.println(e);
Scanner scan = new Scanner(System.in);
System.out.println("Enter new file name : ");
infile[i] = scan.nextLine();
}
}
}
}
}
公共类模拟{ 公共静态无效main（String [] args）{
Scanner scan = new Scanner(System.in);
Thread Th = Thread.currentThread();
System.out.printf("%s >> Enter max seats = ", Th.getName());
System.out.println();
int max_seat = scan.nextInt();
System.out.printf("%s >> Enter checkpoints = ", Th.getName());
System.out.println();
int checkpoint = scan.nextInt();
Userinput U = new Userinput();
BusLine Airport = new BusLine(max_seat, checkpoint, "A");
BusLine City = new BusLine(max_seat, checkpoint, "C");
CyclicBarrier CB = new CyclicBarrier(4);
U.input();
TicketCounter[] T = {
new TicketCounter("T1", U.getDATA1(), Airport, City),
new TicketCounter("T2", U.getDATA2(), Airport, City),
new TicketCounter("T3", U.getDATA3(), Airport, City)};
for (int i = 0; i < 3; i++) {
T[i].setCyclicBarrier(CB);
T[i].start();
}
try {
CB.await();
Airport.printAirportCheckpoint();
City.printCityCheckpoint();
CB.await();
}catch (Exception e){}
for (int i = 0; i < 3; i++) {
try {
T[i].join();
} catch (Exception e) {
System.err.println(e);
}
}
Airport.BusBoundA();
City.BusBoundC();
}
}