I don't understand runnable, it is so confusing

Question

I have got this code that connect to a server and send message, it works perfectly, I just don't get the idea of runnable. Is the code within the run(){ } is executed in a loop? I tried puttin a log.e inside, and it only prints once, so how does it actually work?

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);      
    new Thread(new ClientThread()).start();
}

public void onClick(View view) {
    try {
        EditText et = (EditText) findViewById(R.id.EditText01);
        String str = et.getText().toString();
        PrintWriter out = new PrintWriter(new BufferedWriter(
                new OutputStreamWriter(socket.getOutputStream())),
                true);
        out.println(str);
    } catch (UnknownHostException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } catch (Exception e) {
        e.printStackTrace();
    }
}

class ClientThread implements Runnable {

    @Override
    public void run() {
        Log.e("in try","run");
        try {
            InetAddress serverAddr = InetAddress.getByName(SERVER_IP);
            socket = new Socket(serverAddr, SERVERPORT);
        } catch (UnknownHostException e1) {
            e1.printStackTrace();
        } catch (IOException e1) {
            e1.printStackTrace();
        }
    }
}

}

Answer 1

Is the code within the run(){ } is executed in a loop?

• No, the code that you provided at least will not run in a loop.

Note: You can use other ways to call it in a loop like handler can post it again to the handler with the call to - handler.postDelayed(this, 1000); every 1000 ms.

public interface Runnable -

Represents a command that can be executed. Often used to run code in a different Thread.

Public Methods:

public abstract void run ()

Starts executing the active part of the class' code. This method is called when a thread is started that has been created with a class which implements Runnable.

Basics of Runnable -

Using Runnable Interface, you can run the class several times.

Example -

class ClientThread implements Runnable {

    @Override
    public void run() {

         Log.e("in try","run");
         //Some code
    }
  }

//Multiple threads share the same object.
ClientThread  rc = new ClientThread ();
Thread t1 = new Thread(rc);
t1.start();
Thread.sleep(1000); // Waiting for 1 second before starting next thread
Thread t2 = new Thread(rc);
t2.start();
Thread.sleep(1000); // Waiting for 1 second before starting next thread
Thread t3 = new Thread(rc);
t3.start(); 

Reference: Runnable in Android.