Threads / Scheduler
Executor
ExecutorService allows you to run asynchron tasks without having to deal with threads directly.
/**
* Creating a thread is an expensive operation ...
* and it should be minimized.
*
* Having worker threads minimizes the overhead ...
* because executor service has to create the thread pool only once.
*
* In a fixed thread-pool, the executor service makes sure ...
* that the pool always has the specified number of threads running.
*/
package com.minte9.threads.scheduler;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class Executor {
public static void main(String[] args) {
ExecutorService service = Executors.newFixedThreadPool(2);
// fixed pool = 2 thread at the same time
Runnable task1 = () -> { // loop
while(true) {
System.out.println(
"Task 1 / " + Thread.currentThread().getName()
);
sleep(2);
}
};
Runnable task2 = () -> { // only once
System.out.println(
"Task 2 / " + Thread.currentThread().getName()
);
sleep(1);
};
Runnable task3 = () -> { // loop
while(true) {
System.out.println(
"Task 3 / " + Thread.currentThread().getName()
);
sleep(1);
}
};
service.submit(task1);
service.submit(task2);
service.submit(task3);
service.shutdown();
/*
Task 1 / pool-1-thread-1
Task 2 / pool-1-thread-2 - Look Here
Task 1 / pool-1-thread-1
Task 3 / pool-1-thread-2
Task 1 / pool-1-thread-1
Task 3 / pool-1-thread-2
...
*/
}
public static void sleep(int seconds) {
try {
TimeUnit.SECONDS.sleep(seconds);
} catch (InterruptedException ex) {}
}
}
Scheduled
ScheduledExecutorService can run a task perioadically (and after an initial delay).
/**
* ScheduledExecutorService can run a task perioadically ...
* or after an initial delay.
*/
package com.minte9.threads.scheduler;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
public class Scheduled {
public static void main(String[] args)
throws InterruptedException {
// Create a service with 1 thread
ScheduledExecutorService service =
Executors.newScheduledThreadPool(1);
// Schedule a task to run repeatedly
service.scheduleAtFixedRate(() -> {
System.out.println(new Date() + " - scheduled");
}, 5L, 10L, TimeUnit.SECONDS); // 5s, 10s delay
// Main thread
while(true) {
System.out.println(new Date() + " - main");
TimeUnit.SECONDS.sleep(10); // 10S
}
/*
Tue Oct 05 17:54:13 EEST 2021 - main
Tue Oct 05 17:54:18 EEST 2021 - scheduled
Tue Oct 05 17:54:23 EEST 2021 - main
Tue Oct 05 17:54:28 EEST 2021 - scheduled
...
*/
}
}
Last update: 61 days ago
