Example of ScheduledThreadPoolExecutor in Java
April 21, 2019
ScheduledThreadPoolExecutor belongs to java.util.concurrent package. While creating object of ScheduledThreadPoolExecutor, we need to pass core pool Size. ScheduledThreadPoolExecutor executes and schedules task. We create its object as following.
ScheduledThreadPoolExecutor stpe = new ScheduledThreadPoolExecutor(corePoolSize);
ScheduledThreadPoolExecutor at a time.
1.
execute method of ScheduledThreadPoolExecutor will execute only Runnable task.
stpe.execute(new ScheduledThreadPoolExecutorTest().new RunnableThread());
schedule method of ScheduledThreadPoolExecutor can accept Callable and Runnable task both. It returns ScheduledFuture instance.
ScheduledFuture<Integer> sf = stpe.schedule(new ScheduledThreadPoolExecutorTest().new CallableThread(), 2, TimeUnit.SECONDS);
package com.concretepage;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
public class ScheduledThreadPoolExecutorTest {
public static void main(String... args) throws InterruptedException, ExecutionException {
int corePoolSize=2;
//creates ScheduledThreadPoolExecutor object with number of thread 2
ScheduledThreadPoolExecutor stpe = new ScheduledThreadPoolExecutor(corePoolSize);
//starts runnable thread
stpe.execute(new ScheduledThreadPoolExecutorTest().new RunnableThread());
//starts callable thread that will start after 2 seconds
ScheduledFuture<Integer> sf = stpe.schedule(new ScheduledThreadPoolExecutorTest().new CallableThread(), 2,
TimeUnit.SECONDS);
//gets value returned by callable thread
int res=sf.get();
System.out.println("value returned by Callable Thread."+res);
//returns active thread
int activeCnt=stpe.getActiveCount();
System.out.println("activeCnt:"+activeCnt);
//stops all the threads in ScheduledThreadPoolExecutor
stpe.shutdownNow();
System.out.println(stpe.isShutdown());
}
//runnable thread
class RunnableThread implements Runnable {
@Override
public void run() {
int cnt = 0;
for (; cnt < 5; cnt++) {
System.out.println("run:" + cnt);
}
}
}
// callable thread that will return value
class CallableThread implements Callable<Integer> {
@Override
public Integer call() throws Exception {
int cnt = 0;
for (; cnt < 5; cnt++) {
System.out.println("call:" + cnt);
}
return cnt;
}
}
}
run:0 run:1 run:2 run:3 run:4 call:0 call:1 call:2 call:3 call:4 value returned by Callable Thread.5 activeCnt:0 true
