从在线程中实现 Runnable 接口创建对象 - Java

Question

I'm new in Java and threading.

Is there any different to create an runnable object as Runnable and ThreadState :

class ThreadState implements Runnable {

  public void run() {
    System.out.println("xxxxx");
  }
  public static void main(String args[]) {
    Runnable r1 = new ThreadState();
    Thread t1 = new Thread(r1);
    t1.start();
  }
}

And

class ThreadState implements Runnable {

  public void run() {
    System.out.println("xxxxx");
  }
  public static void main(String args[]) {
    ThreadState r1 = new ThreadState();
    Thread t1 = new Thread(r1);
    t1.start();
  }
}

Thanks!

Answer 1

In your code, r1 is neither a Runnable nor a ThreadState .

It is just a reference to an object of that type.

In both cases, with the execution of new ThreadState() you create an instance of ThreadState that is also an instance of Runnable .

As a result, your code snippets are equivalent.

public class ThreadState implements Runnable 
{
  @Override
  public final void run() 
  {
    System.out.println( "xxxxx" );
  }

  public static final void main( String... args ) 
  {
    Runnable r1 = new ThreadState();
    if( r1 instanceof ThreadState ) System.out.println( "r1 is ThreadState" ); // will be printed
    Thread t1 = new Thread( r1 );
    t1.start();
  }
}

vs.

public class ThreadState implements Runnable 
{
  @Override
  public final void run() 
  {
    System.out.println( "xxxxx" );
  }
  public static final void main( String... args[] ) 
  {
    ThreadState r1 = new ThreadState();
    if( r1 instanceof Runnable ) System.out.println( "r1 is Runnable" ); // will be printed
    Thread t1 = new Thread( r1 );
    t1.start();
  }
}