System.exit(0) doesnt close all my activities?

System.exit(0);

is a bad way of termination of android apps. Android manages it in its own os

You can bring up the Home application by its corresponding Intent:

Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_HOME);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);

hope this helps

EDIT :-

Then I suppose you are aiming at finishing all the stacked up activity..

Here it is :-

Closing all the previous activities as follows:

Intent intent = new Intent(this, MainActivity.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.putExtra("Exit me", true);
startActivity(intent);
finish();

Then in MainActivity onCreate() method add this to finish the MainActivity

if( getIntent().getBooleanExtra("Exit me", false)){
    finish();
}

The result will be same as above, but because all your stacked up activities are closed, when you come back to you app it must start from your main activity i.e launcher activity.

Hope this helps.

Don't use System.exit.

If you want user to close app from any Activity I suggest using startActivityForResult, checking returned value in onActivityResult in first Activity and calling finish() there too.

You can either simulate hitting the home button:

Intent intent = new Intent(Intent.ACTION_MAIN);
intent.addCategory(Intent.CATEGORY_HOME);
intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
startActivity(intent);

but this will not close the app..

to close it, you can do as https://stackoverflow.com/a/9735524/1434631