Creating a new Thread for every Job in Java may cause performance and memory-related problems. To overcome these problems we can use Thread Pool in Java. A Thread Pool is a pool/ collection of already created threads.
In Java 1.5v Thread pool framework is introduced to implement thread pool. Thread Pool framework in also known as the Executor framework in Java.
Creating Thread Pool in Java
ExecutorService threadPool = Executors.newFixedThreadPool(3);
Submit a Job to Thread Pool
We can submit a Runnable job by using submit method
Future<?> submit( @NotNull Runnable task )Shutdown Thread Pool
we can shutdown thread pool / ExecutorService by using shutdown method
void shutdown()Thread Pool Example
package thread;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
class Print implements Runnable {
String name;
public Print(String name) {
this.name = name;
}
@Override
public void run() {
System.out.println( name + " Job started by thread" + Thread.currentThread().getName());
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
}
System.out.println(name + " Job Completed By Thread" + Thread.currentThread().getName());
}
}
public class ThreadPoolExample {
public static void main(String[] args) {
Print[] jobs = {
new Print("The Code Data1"),
new Print("The Code Data2"),
new Print("The Code Data3"),
new Print("The Code Data4"),
};
ExecutorService threadPool = Executors.newFixedThreadPool(3);
for(Print job:jobs){
threadPool.submit(job);
}
threadPool.shutdown();
}
}
package thread;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
class Print implements Runnable {
String name;
public Print(String name) {
this.name = name;
}
@Override
public void run() {
System.out.println( name + " Job started by thread" + Thread.currentThread().getName());
try {
Thread.sleep(5000);
} catch (InterruptedException e) {
}
System.out.println(name + " Job Completed By Thread" + Thread.currentThread().getName());
}
}
public class ThreadPoolExample {
public static void main(String[] args) {
Print[] jobs = {
new Print("The Code Data1"),
new Print("The Code Data2"),
new Print("The Code Data3"),
new Print("The Code Data4"),
};
ExecutorService threadPool = Executors.newFixedThreadPool(3);
for(Print job:jobs){
threadPool.submit(job);
}
threadPool.shutdown();
}
}
In the above example, 3 threads are responsible to execute 4 Runnable jobs.
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