use Collections' isEmpty() to test for emptiness

This should make the code intent clearer and more standard Java.

app/src/main/java/org/fdroid/fdroid/NotificationHelper.java

@@ -199,7 +199,7 @@ class NotificationHelper {
 
         Notification notification;
         if (updates.size() != 1 || useStackedNotifications()) {
-            if (updates.size() == 0) {
+            if (updates.isEmpty()) {
                 // No updates, remove summary
                 notificationManager.cancel(GROUP_UPDATES, NOTIFY_ID_UPDATES);
             } else {
@@ -208,7 +208,7 @@ class NotificationHelper {
             }
         }
         if (installed.size() != 1 || useStackedNotifications()) {
-            if (installed.size() == 0) {
+            if (installed.isEmpty()) {
                 // No installed, remove summary
                 notificationManager.cancel(GROUP_INSTALLED, NOTIFY_ID_INSTALLED);
             } else {

app/src/main/java/org/fdroid/fdroid/Provisioner.java

@@ -64,8 +64,8 @@ public class Provisioner {
             List<ProvisionPlaintext> plaintexts = p.extractProvisionsPlaintext(files);
             List<Provision> provisions = p.parseProvisions(plaintexts);
 
-            if (provisions == null || provisions.size() == 0) {
+            if (provisions == null || provisions.isEmpty()) {
-                Utils.debugLog(TAG, "Provision dir does not contain any provisions: '" + provisionDir.getAbsolutePath() + "' moving on ...");
+                Utils.debugLog(TAG, "Provision dir is empty: '" + provisionDir.getAbsolutePath() + "' moving on ...");
             } else {
                 int cleanupCounter = 0;
                 for (Provision provision : provisions) {

app/src/main/java/org/fdroid/fdroid/data/AppProvider.java

@@ -638,7 +638,7 @@ public class AppProvider extends FDroidProvider {
         // Put in a Set to remove duplicates
         final Set<String> keywordSet = new HashSet<>(Arrays.asList(query.split("\\s")));
 
-        if (keywordSet.size() == 0) {
+        if (keywordSet.isEmpty()) {
             return new AppQuerySelection();
         }
 

app/src/main/java/org/fdroid/fdroid/data/QueryBuilder.java

@@ -143,7 +143,7 @@ abstract class QueryBuilder {
     }
 
     private String orderBySql() {
-        if (orderBys.size() == 0) {
+        if (orderBys.isEmpty()) {
             return "";
         }
         return " ORDER BY " + TextUtils.join(", ", orderBys);

app/src/main/java/org/fdroid/fdroid/data/RepoPersister.java

@@ -182,12 +182,12 @@ public class RepoPersister {
     private void calcApkCompatibilityFlags(List<Apk> apks) {
         for (final Apk apk : apks) {
             final List<String> reasons = checker.getIncompatibleReasons(apk);
-            if (reasons.size() > 0) {
+            if (reasons.isEmpty()) {
-                apk.compatible = false;
-                apk.incompatibleReasons = reasons.toArray(new String[reasons.size()]);
-            } else {
                 apk.compatible = true;
                 apk.incompatibleReasons = null;
+            } else {
+                apk.compatible = false;
+                apk.incompatibleReasons = reasons.toArray(new String[reasons.size()]);
             }
         }
     }

app/src/main/java/org/fdroid/fdroid/data/RepoProvider.java

@@ -80,7 +80,7 @@ public class RepoProvider extends FDroidProvider {
 
             boolean haveTriedWithoutPath = false;
             while (repo == null && !haveTriedWithoutPath) {
-                if (pathSegments.size() == 0) {
+                if (pathSegments.isEmpty()) {
                     haveTriedWithoutPath = true;
                 } else {
                     pathSegments.remove(pathSegments.size() - 1);
@@ -99,7 +99,11 @@ public class RepoProvider extends FDroidProvider {
                                          String address, String[] projection) {
             List<Repo> repos = findBy(
                     context, Cols.ADDRESS, address, projection);
-            return repos.size() > 0 ? repos.get(0) : null;
+            if (repos.isEmpty()) {
+                return null;
+            } else {
+                return repos.get(0);
+            }
         }
 
         public static List<Repo> all(Context context) {

app/src/main/java/org/fdroid/fdroid/views/AppDetailsRecyclerViewAdapter.java

@@ -153,13 +153,13 @@ public class AppDetailsRecyclerViewAdapter
         addItem(VIEWTYPE_DONATE);
         addItem(VIEWTYPE_LINKS);
         addItem(VIEWTYPE_PERMISSIONS);
-        if (versions.size() > 0) {
+        if (versions.isEmpty()) {
+            addItem(VIEWTYPE_NO_VERSIONS);
+        } else {
             addItem(VIEWTYPE_VERSIONS);
             if (showVersions) {
                 setShowVersions(true);
             }
-        } else {
-            addItem(VIEWTYPE_NO_VERSIONS);
         }
 
         notifyDataSetChanged();
@@ -563,7 +563,7 @@ public class AppDetailsRecyclerViewAdapter
 
             updateAntiFeaturesWarning();
             buttonPrimaryView.setText(R.string.menu_install);
-            buttonPrimaryView.setVisibility(versions.size() > 0 ? View.VISIBLE : View.GONE);
+            buttonPrimaryView.setVisibility(versions.isEmpty() ? View.GONE : View.VISIBLE);
             buttonSecondaryView.setText(R.string.menu_uninstall);
             buttonSecondaryView.setVisibility(app.isUninstallable(context) ? View.VISIBLE : View.INVISIBLE);
             buttonSecondaryView.setOnClickListener(new View.OnClickListener() {

app/src/test/java/org/fdroid/fdroid/data/RepoXMLHandlerTest.java

@@ -840,7 +840,7 @@ public class RepoXMLHandlerTest {
         for (App app : apps) {
             if (expectedAntiFeatures.containsKey(app.packageName)) {
                 List<String> antiFeatures = expectedAntiFeatures.get(app.packageName);
-                if (antiFeatures.size() == 0) {
+                if (antiFeatures.isEmpty()) {
                     assertNull(app.antiFeatures);
                 } else {
                     List<String> actualAntiFeatures = new ArrayList<>();

app/src/test/java/org/fdroid/fdroid/updater/IndexV1UpdaterTest.java

@@ -423,7 +423,7 @@ public class IndexV1UpdaterTest extends FDroidProviderTest {
         for (String field : allowed) {
             fields.remove(field);
         }
-        if (fields.size() > 0) {
+        if (!fields.isEmpty()) {
             String sb = String.valueOf(instance.getClass()) + " has fields not setup for Jackson: " +
                     TextUtils.join(", ", fields) + "\nRead class javadoc for more info.";
             fail(sb);