How to get Thread ID in Java with Example

ThreadId can be obtained from the Thread.currentThread()  method.

Read Also :   Multithreading Interview Questions in Java


What is thread ID in java?

According to Oracle docs , thread ID is the identifier of the thread.  The thread ID is a positive long number generated when the thread is created.
Note : thread ID  remains unique and unchanged during the lifetime of the thread. When a thread is terminated then its thread ID may be reused.

There are two ways to get thread ID in Java , one is by getting the reference of the current thread i.e Thread.currentThread() and the other is using Thread.get

currentThread() method in Java

currentThread() is a static method , returns a reference to the currently executing thread object.

After getting the reference of the current thread , we will call the getId() method on Thread class.

getId() method in Java

getId() will return the unique identifier of current thread which is a positive long value.

import java.lang.*;

public class ThreadIdExample   {
    
    public static void main(String[] args) { 

        WorkerThread workerthreadobject = new WorkerThread();

        //  below is the first constructor : setting name also

        Thread  t1 = new Thread(workerthreadobject);

        t1.setName("First Thread");

        t1.start();

        //  below is the second constructor : setting name as argument    

        Thread  t2 = new Thread(workerthreadobject , "Second Thread");

        t2.start();

      
       // below we will not set any name of the thread
  
       Thread  t3 = new Thread(workerthreadobject);
        t3.start();



// Getting the current thread object i.e Main thread 



Thread currentThread = Thread.currentThread();



// Printing Main thread : name and id  



System.out.println("Executing  thread : " + currentThread.getName()) ;

       System.out.println("id of the thread is " + currentThread.getId());   

 }
}

 class WorkerThread implements Runnable{
    

    @Override 
    public void run() { 

        // get current thread instance

        Thread t = Thread.currentThread();

        // call thread.getId() on the current t instance

        System.out.println("WorkerThread details : Name - "+ t.getName()); 

        System.out.println("Thread Id of Worker Thread - " + t.getId());

 }
}

Output :

WorkerThread details : Name - First Thread
Thread Id of Worker Thread - 7
WorkerThread details : Name - Second Thread
Thread Id of Worker Thread - 8
Executing  thread : main
id of the thread is 1
WorkerThread details : Name - Thread-1
Thread Id of Worker Thread - 9

Please mention in comments if you know any other way of getting thread ID.