Apply a few android studio fixes

F-Droid/src/org/fdroid/fdroid/compat/Compatibility.java

@@ -5,16 +5,16 @@ import android.os.Build;
 public abstract class Compatibility {
 
     // like minSdkVersion
-    protected static final boolean hasApi(int apiLevel) {
+    protected static boolean hasApi(int apiLevel) {
         return getApi() >= apiLevel;
     }
 
     // like maxSdkVersion
-    protected static final boolean upToApi(int apiLevel) {
+    protected static boolean upToApi(int apiLevel) {
         return (apiLevel < 1 || getApi() <= apiLevel);
     }
 
-    protected static final int getApi() {
+    protected static int getApi() {
         return Build.VERSION.SDK_INT;
     }
 

F-Droid/src/org/fdroid/fdroid/compat/SupportedArchitectures.java

@@ -1,6 +1,5 @@
 package org.fdroid.fdroid.compat;
 
-import android.annotation.TargetApi;
 import android.os.Build;
 
 public class SupportedArchitectures extends Compatibility {
@@ -8,6 +7,7 @@ public class SupportedArchitectures extends Compatibility {
     /**
      * The most preferred ABI is the first element in the list.
      */
+    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
     @SuppressWarnings("deprecation")
     public static String[] getAbis() {
         if (hasApi(21)) {

F-Droid/src/org/fdroid/fdroid/data/App.java

@@ -21,10 +21,7 @@ import java.io.IOException;
 import java.io.InputStream;
 import java.security.cert.Certificate;
 import java.security.cert.CertificateEncodingException;
-import java.util.ArrayList;
-import java.util.Arrays;
 import java.util.Date;
-import java.util.List;
 import java.util.jar.JarEntry;
 import java.util.jar.JarFile;
 

F-Droid/src/org/fdroid/fdroid/installer/RootInstaller.java

@@ -47,13 +47,11 @@ public class RootInstaller extends Installer {
     }
 
     private Shell.Builder createShellBuilder() {
-        Shell.Builder shellBuilder = new Shell.Builder()
+        return new Shell.Builder()
                 .useSU()
                 .setWantSTDERR(true)
                 .setWatchdogTimeout(30)
                 .setMinimalLogging(false);
-
-        return shellBuilder;
     }
 
     @Override

F-Droid/src/org/fdroid/fdroid/localrepo/LocalRepoKeyStore.java

@@ -272,8 +272,7 @@ public class LocalRepoKeyStore {
     private KeyPair generateRandomKeypair() throws NoSuchAlgorithmException {
         KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance(DEFAULT_KEY_ALGO);
         keyPairGenerator.initialize(DEFAULT_KEY_BITS);
-        KeyPair keyPair = keyPairGenerator.generateKeyPair();
+        return keyPairGenerator.generateKeyPair();
-        return keyPair;
     }
 
     private Certificate generateSelfSignedCertChain(KeyPair kp, X500Name subject)

F-Droid/src/org/fdroid/fdroid/updater/SignedRepoUpdater.java

@@ -119,12 +119,12 @@ public class SignedRepoUpdater extends RepoUpdater {
     @Override
     protected File getIndexFromFile(File downloadedFile) throws
             UpdateException {
-        Date updateTime = new Date(System.currentTimeMillis());
+        final Date updateTime = new Date(System.currentTimeMillis());
         Log.d(TAG, "Getting signed index from " + repo.address + " at " +
                 Utils.formatLogDate(updateTime));
 
-        File indexJar  = downloadedFile;
+        final File indexJar = downloadedFile;
-        File indexXml  = null;
+        File indexXml = null;
 
         // Don't worry about checking the status code for 200. If it was a
         // successful download, then we will have a file ready to use:

F-Droid/src/org/fdroid/fdroid/views/fragments/SelectLocalAppsFragment.java

@@ -141,14 +141,13 @@ public class SelectLocalAppsFragment extends ListFragment
         } else {
             baseUri = InstalledAppProvider.getSearchUri(mCurrentFilterString);
         }
-        CursorLoader loader = new CursorLoader(
+        return new CursorLoader(
                 this.getActivity(),
                 baseUri,
                 InstalledAppProvider.DataColumns.ALL,
                 null,
                 null,
                 InstalledAppProvider.DataColumns.APPLICATION_LABEL);
-        return loader;
     }
 
     @Override

F-Droid/src/org/fdroid/fdroid/views/swap/ConfirmReceiveSwapFragment.java

@@ -88,7 +88,6 @@ public class ConfirmReceiveSwapFragment extends Fragment implements ProgressList
         }
     }
 
-    @NonNull
     private Repo ensureRepoExists() {
         if (!newRepoConfig.isValidRepo()) {
             return null;