# Threads in Java (with example)

Paul Tomoiu

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Examples,

Threads,

Spring

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Published 2022-12-03

This tutorial will explain to you how to use threads in Java and will present you an example.

Multithreading refers to two or more tasks executing concurrently within a single OS 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.

There are two ways to create thread in java:

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

NOTES:

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

A thread could be in the following states:

NEW – The thread is created, but not started
RUNNABLE – either running or ready for execution (but it's waiting for resource allocation)
BLOCKED – waiting to acquire a monitor lock to enter or re-enter a synchronized block/method
WAITING – waiting for some other thread to perform a particular action without any time limit
TIMED_WAITING – waiting for some other thread to perform a specific action for a specified period
TERMINATED – has completed its execution (normally or with an exception)

Here is an example of using Threads 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 ThreadClass extends Thread {
       private Thread thread;
       private String threadName;
        
       ThreadClass( String name) {
          threadName = name;
          System.out.println("Creating " +  threadName );
       }
        
       public void run() {
          PrintValues printValues = new PrintValues();
          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);
              thread.start ();
          }
       }
    }

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

And here is the result of the execution: