Exploring Thread API

How to know the currently executing Thread

Thread API provides a method class currentThread(), which returns the reference of the currently executing thread

Syntax:

     public static Thread currentThread()

Since currentThread() is a static method, we can call it by using Thread class like

     Thread.currentThread()

Example

class MyThread extends Thread{
 public void run(){
  System.out.println("In run method, My name is " + currentThread());
 }

 public static void main(String args[]){
  MyThread t1 = new MyThread();
  MyThread t2 = new MyThread();
  t1.start();
  t2.start();
  System.out.println("In main method, My name is " + Thread.currentThread());
 }
}

    

Possible Outcome 

In run method, My name is Thread[Thread-0,5,main]
In main method, My name is Thread[main,5,main] 
In run method, My name is Thread[Thread-1,5,main] 

 

Observation

See the format Thread[Thread-0,5,main]

Thread-0 : specifies the thread name, If you don't set a name to the Thread, it will follow default naming conventions

5 : Priority of the Thread., If you don't set a priority to a thread, by default it has 5, will

main : specifies the group name of the thread

Setting and get the name of a Thread

Every thread has a name associated with it. Thread API provides getName() and setName() methods to retrieve the thread name and set a name to thread respectively.

If user not set the name explicitly, then it will assign with a default name at the time of construction.

Setting a name to Thread

public final void setName(String name)

Changes the name of this thread to be equal to the argument name. Since the setName() is a final method, so you can't override it.

Getting the name of a Thread

public final String getName()

Returns this thread's name. Since the getName() is a final method, so you can't override it.

class MyThread extends Thread{
 public void run(){
  System.out.println("Current Runing Thread is " + Thread.currentThread());
  System.out.println("Current Thread name is " + Thread.currentThread().getName());
 }

 public static void main(String args[]){
  MyThread t1 = new MyThread();
  t1.setName("MyThread1");
  t1.start();
 }
}

Output

Current Runing Thread is Thread[MyThread1,5,main]
Current Thread name is MyThread1

Points to be noted while setting the Thread name

1. Set the thread name before calling the start(). Of course you can can set the name to a thread after calling thread start method, but it is not preferable.

Example

class MyThread extends Thread{
 public void run(){
  System.out.println("Current Running Thread is " + Thread.currentThread());
  System.out.println("Current Thread name is " + Thread.currentThread().getName());
 }

 public static void main(String args[]){
  MyThread t1 = new MyThread();
  t1.setName("MyThread1");
  t1.start();
  for(int i=0; i < 10000; i++){
   t1.setName("MyThread" + i);
  }
  System.out.println(t1.getName());
 }
}

Output

Current Running Thread is Thread[MyThread14,5,main]
Current Thread name is MyThread328
MyThread9999

See the above output in the bold letters, if thread name changed, when you are trying to perform some operations based on Thread name, then you will face problems.

2. Do not change the name of main thread. It will cause unexpected results

3. You can give same name to multiple threads, but give unique name to the threads, to identify differently

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