# Create a Daemon in Java (with example)

Paul Tomoiu

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Examples,

Daemons,

Threads,

Concurrency

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Published 2022-12-03

This tutorial will explain to you how we can create a daemon process in Java. This article will show you an example as well.

Multithreading refers to two or more tasks executing concurrently within a single process. A thread is an independent path of execution within a process. Many threads can run concurrently within a process. There can be multiple processes inside the OS.

NOTES:

Cost of communication between the threads is low.
Threads share the same address space and therefore can share both data and code
Threads allow different tasks to be performed concurrently

There are two ways for creating thread in java:

by extending the Thread class (java.lang.Thread)
by implementing the Runnable interface (java.lang.Runnable)

Info

A "daemon" in Java is an ordinary thread marked as "daemon" using setDaemon(true) method !

Daemon threads are Low Priority threads. A thread that executes main logic of the project is called non-daemon thread. Every user defined thread is created as non-daemon thread by default, because main thread is a non-daemon thread. Here is an example of creating daemons in Java using the "extends Thread" method (the "implements Runnable" method is similar):

package threads.java.example;
 
class PrintValues {
 
    static void printValues(String threadName){
         
        for (int i = 1; i < 12; i++) {
             System.out.println("printValues   --->   "  + i + " >>> FROM : "+threadName);
        }
   }
}

package threads.java.example;
 
public class ThreadDaemonClass extends Thread {
       private Thread thread;
       private String threadName;
        
       ThreadDaemonClass( String name) {
          threadName = name;
          System.out.println("Creating " +  threadName );
       }
        
       public void run() {
          System.out.println(threadName + " is running ...");
         
          PrintValues.printValues(threadName);
           
          System.out.println( threadName + " has been finished.");
       }
        
       public void start () {
          System.out.println("Start " +  threadName );
          if (thread == null) {
              thread = new Thread (this, threadName);
               
              // Sets the Thread as "daemon"
              thread.setDaemon(true);
              thread.start ();
          }
       }
    }

package threads.java.example;
 
public class ThreadsInJavaExample {
 
       public static void main(String args[]) {
          ThreadDaemonClass T1 = new ThreadDaemonClass("Thread A");
          T1.start();
 
          ThreadDaemonClass T2 = new ThreadDaemonClass("Thread B");
          T2.start();
       }   
    }