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Copy pathCountDownLatchDemo.java
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executable file
·81 lines (68 loc) · 2.36 KB
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package com.brianway.learning.java.concurrent;
import java.util.Random;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class CountDownLatchDemo {
static final int SIZE = 10;
public static void main(String[] args) throws Exception {
ExecutorService exec = Executors.newCachedThreadPool();
// All must share a single CountDownLatch object:
CountDownLatch latch = new CountDownLatch(SIZE);
for (int i = 0; i < 10; i++)
exec.execute(new WaitingTask(latch));
for (int i = 0; i < SIZE; i++)
exec.execute(new TaskPortion(latch));
System.out.println("Launched all tasks");
exec.shutdown(); // Quit when all tasks complete
}
}
// Performs some portion of a task:
class TaskPortion implements Runnable {
private static int counter = 0;
private final int id = counter++;
private static Random rand = new Random(47);
private final CountDownLatch latch;
TaskPortion(CountDownLatch latch) {
this.latch = latch;
}
public void run() {
try {
doWork();
latch.countDown();
latch.await();
System.out.println(this + " TaskPortion after await");
} catch (InterruptedException ex) {
// Acceptable way to exit
}
}
public void doWork() throws InterruptedException {
TimeUnit.MILLISECONDS.sleep(rand.nextInt(2000));
System.out.println(this + "completed");
}
public String toString() {
return String.format("%1$-3d ", id);
}
}
// Waits on the CountDownLatch:
class WaitingTask implements Runnable {
private static int counter = 0;
private final int id = counter++;
private final CountDownLatch latch;
WaitingTask(CountDownLatch latch) {
this.latch = latch;
}
public void run() {
try {
latch.await();
System.out.println("Latch barrier passed for " + this);
} catch (InterruptedException ex) {
System.out.println(this + " interrupted");
}
}
public String toString() {
return String.format("WaitingTask %1$-3d ", id);
}
}
/* (Execute to see output) *///:~