Timer timer = new Timer();
timer.scheduleAtFixedRate(new TimerTask() {
    @Override
    public void run() {
        Toast.makeText(MainActivity.this, "Coba", Toast.LENGTH_SHORT).show();
    }
}, 1000, 6000);

runOnUiThread (new Thread(new Runnable() {
    public void run() {
        Toast.makeText(MainActivity.this, "Coba", Toast.LENGTH_SHORT).show();
    }
}));

Thread timer = new Thread(){
    public void run(){
        try{
            sleep(1000);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            //Toast.makeText(MainActivity.this, "Coba", Toast.LENGTH_SHORT).show();
            Log.d(getClass().getSimpleName(), "onCreate: ");
        }
    }
};
timer.start();

new Handler().postDelayed(new Runnable() {
    @Override
    public void run() {
        //Toast.makeText(MainActivity.this, "Coba", Toast.LENGTH_SHORT).show();
        Log.d(getClass().getSimpleName(), "onCreate: ");
    }
}, 4000);