Going to home screen programmatically

Janusz's answer is great.

The only thing I want to add, which is a little too long for a comment, is that you can go to the home screen without having a reference to the current activity.

Janusz's code needs to be called from an Activity or Fragment due to startActivity(),

To get around this, you can store a static reference to your apps Context in your application file:

public class YourApplication extends Application
{

    private static Context mAppContext;

    public void onCreate()
    {
        super.onCreate();
        ...
        YourApplication.mAppContext = getApplicationContext();
    }

    public static Context getContext()
    {
        return mAppContext;
    }

}

Now you can send the user to the device home screen from any class in your app, not just Activities, Fragments, or other Classes with a reference to the current Activity (you can decide whether this is a good or bad thing):

Intent startMain = new Intent(Intent.ACTION_MAIN);
startMain.addCategory(Intent.CATEGORY_HOME);
startMain.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
YourApplication.getContext().startActivity(startMain);

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