Use instanceOf instead of getClass

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/src/main/java/com/wireguard/android/BootShutdownReceiver.java

@@ -21,7 +21,7 @@ public class BootShutdownReceiver extends BroadcastReceiver {
     @Override
     public void onReceive(final Context context, final Intent intent) {
         Application.onHaveBackend(backend -> {
-            if (backend.getClass() != WgQuickBackend.class)
+            if (!(backend instanceof WgQuickBackend))
                 return;
             final String action = intent.getAction();
             if (action == null)

app/src/main/java/com/wireguard/android/activity/BaseActivity.java

@@ -54,7 +54,7 @@ public abstract class BaseActivity extends ThemeChangeAwareActivity {
         super.onCreate(savedInstanceState);
 
         Application.onHaveBackend(backend -> {
-            if (backend.getClass() == GoBackend.class) {
+            if (backend instanceof GoBackend) {
                 final Intent intent = GoBackend.VpnService.prepare(this);
                 if (intent != null)
                     startActivityForResult(intent, 0);

app/src/main/java/com/wireguard/android/activity/SettingsActivity.java

@@ -102,7 +102,7 @@ public class SettingsActivity extends ThemeChangeAwareActivity {
             final PreferenceScreen screen = getPreferenceScreen();
             Application.onHaveBackend(backend -> {
                 for (final Preference pref : wgQuickOnlyPrefs) {
-                    if (backend.getClass() == WgQuickBackend.class)
+                    if (backend instanceof WgQuickBackend)
                         pref.setVisible(true);
                     else
                         screen.removePreference(pref);