GetDeviceId.java

@RequiresPermission("android.permission.READ_PHONE_STATE")
public static String getDeviceId(Context context) {
    String androidId = Settings.Secure.getString(context.getContentResolver(), android.provider.Settings.Secure.ANDROID_ID);
    if (androidId != null)
        return androidId;
    final TelephonyManager tm = (TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE);
    if (tm != null) {
        if (tm.getDeviceId() != null)
            return tm.getDeviceId();
        else
            return tm.getSimSerialNumber();
    } else
        return null;
}