Java Examples - Id of a Thread

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Problem Description:

How to get the Id of the running thread?

Solution:

Following example demonstrates how to get the Id of a running thread using getThreadId() method.

public class Main extends Object implements Runnable {
  private ThreadID var;

  public Main(ThreadID v) {
    this.var = v;
  }

  public void run() {
    try {
      print("var getThreadID =" + var.getThreadID());
      Thread.sleep(2000);
      print("var getThreadID =" + var.getThreadID());
    } catch (InterruptedException x) {
    }
  }

  private static void print(String msg) {
    String name = Thread.currentThread().getName();
    System.out.println(name + ": " + msg);
  }

  public static void main(String[] args) {
    ThreadID tid = new ThreadID();
    Main shared = new Main(tid);

    try {
      Thread threadA = new Thread(shared, "threadA");
      threadA.start();

      Thread.sleep(500);

      Thread threadB = new Thread(shared, "threadB");
      threadB.start();

      Thread.sleep(500);

      Thread threadC = new Thread(shared, "threadC");
      threadC.start();
    } catch (InterruptedException x) {
    }
  }
}

class ThreadID extends ThreadLocal {
  private int nextID;

  public ThreadID() {
    nextID = 10001;
  }

  private synchronized Integer getNewID() {
    Integer id = new Integer(nextID);
    nextID++;
    return id;
  }


  protected Object initialValue() {
    print("in initialValue()");
    return getNewID();
  }

  public int getThreadID() {
    Integer id = (Integer) get();
    return id.intValue();
  }

  private static void print(String msg) {
    String name = Thread.currentThread().getName();
    System.out.println(name + ": " + msg);
  }
}

Result:

The above code sample will produce the following result.

threadA: in initialValue()
threadA: var getThreadID =10001
threadB: in initialValue()
threadB: var getThreadID =10002
threadC: in initialValue()
threadC: var getThreadID =10003
threadA: var getThreadID =10001
threadB: var getThreadID =10002
threadC: var getThreadID =10003


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