如何使用线程运行类的方法

Question

If I do the following, I will be able to create an object as a thread and run it.

class ThreadTest
{
   public static voic main(String[] args)
   {
      HelloThread hello = new HelloThread();
      Thread t = new Thread(hello);
      t.start();       
   }
}

class HelloThread extends Thread
{
   public void run()
   {
      System.out.println(" Hello ");
   }
}

Now, if my HelloThread class has a another method call runThisPlease() , how are we supposed to run it with a thread?

Example:

class HelloThread extends Thread
{
   public void run()
   {
      System.out.println(" Hello ");
   }

   public void runThisPlease(String input)
   {
      System.out.println (" Using thread on another class method: " + input );
   }
}

Que: When I try Thread t = new Thread(hello.runThisPlease()); , it doesn't work. So how can we call the method runThisPlease() using a thread?

Edit: Argument needed in method for runThisPlease() ;

Answer 1

In java 8 you can use

Thread t = new Thread(hello::runThisPlease);

hello::runThisPlease will be converted to a Runnable with a run method that calls hello.runThisPlease(); .

---

If your want to call a method, that needs parameters, eg System.out.println , you can of course use a normal lambda expression too:

final String parameter = "hello world";
Thread t = new Thread(() -> System.out.println(parameter));

---

If you use a java version < 8, you can of course replace the method reference / lambda expression with anonymus inner classes that extend Runnable (which is what a java8 compiler does, AFAIK), see other answers.

However you can also use a anonymus inner class that extends Thread :

final HelloThread hello = //...
Thread t = new Thread() {
    @Override
    public void run() {
        hello.runThisPlease();
    }
};

Answer 2

Simply calling the runThisPlease() from within the run() method will make it part of a new thread.

Try this:

class HelloThread extends Thread
{
   public void run()
   {
      System.out.println(" Hello .. Invoking runThisPlease()");
      runThisPlease();
   }

   public void runThisPlease()
   {
      System.out.println (" Using thread on another class method ");
   }
}

Answer 3

You have to only call this method inside run() method.

public void run(){
  System.out.println(" Hello ");
  runThisPlease();
}

If you want to pass some argument then you can use below code

String str = "Welcome"; 

Thread t = new Thread(new Runnable() {
public void run() {
    System.out.println(str); 
}});

Answer 4

Things are maybe more clear if you use the Runnable interface:

public class HelloThread implements Runnable
{
    @Override
    public void run() {
       // executed when the thread is started
       runThisPlease();
    }

    public void runThisPlease() {...}
}

To launch this call:

Thread t=new Thread(new HelloThread());
t.start();

The Thread class can not see your extra method because it is not part of the Runnable interface. As a convenience Thread implements Runnable but I don't think it helps in clarity :(