Merge "Cleanup IME subtype switching controller and tests" into main
diff --git a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
index 3f296ca..39262c5 100644
--- a/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
+++ b/services/core/java/com/android/server/inputmethod/InputMethodManagerService.java
@@ -1300,9 +1300,8 @@
 
             final InputMethodSettings settings = InputMethodSettingsRepository.get(mCurrentUserId);
 
-            mSwitchingController =
-                    InputMethodSubtypeSwitchingController.createInstanceLocked(context,
-                            settings.getMethodMap(), settings.getUserId());
+            mSwitchingController = new InputMethodSubtypeSwitchingController(context,
+                    settings.getMethodMap(), settings.getUserId());
             mHardwareKeyboardShortcutController =
                     new HardwareKeyboardShortcutController(settings.getMethodMap(),
                             settings.getUserId());
@@ -3049,8 +3048,8 @@
         if (userId == mSwitchingController.getUserId()) {
             mSwitchingController.resetCircularListLocked(settings.getMethodMap());
         } else {
-            mSwitchingController = InputMethodSubtypeSwitchingController.createInstanceLocked(
-                    mContext, settings.getMethodMap(), userId);
+            mSwitchingController = new InputMethodSubtypeSwitchingController(mContext,
+                    settings.getMethodMap(), userId);
         }
         // TODO: Instantiate mHardwareKeyboardShortcutController for each user.
         if (userId == mHardwareKeyboardShortcutController.getUserId()) {
@@ -5320,8 +5319,8 @@
         if (userId == mSwitchingController.getUserId()) {
             mSwitchingController.resetCircularListLocked(settings.getMethodMap());
         } else {
-            mSwitchingController = InputMethodSubtypeSwitchingController.createInstanceLocked(
-                    mContext, settings.getMethodMap(), mCurrentUserId);
+            mSwitchingController = new InputMethodSubtypeSwitchingController(mContext,
+                    settings.getMethodMap(), mCurrentUserId);
         }
         // TODO: Instantiate mHardwareKeyboardShortcutController for each user.
         if (userId == mHardwareKeyboardShortcutController.getUserId()) {
diff --git a/services/core/java/com/android/server/inputmethod/InputMethodSubtypeSwitchingController.java b/services/core/java/com/android/server/inputmethod/InputMethodSubtypeSwitchingController.java
index 770e3b2..bf9621f 100644
--- a/services/core/java/com/android/server/inputmethod/InputMethodSubtypeSwitchingController.java
+++ b/services/core/java/com/android/server/inputmethod/InputMethodSubtypeSwitchingController.java
@@ -48,15 +48,20 @@
     private static final int NOT_A_SUBTYPE_ID = InputMethodUtils.NOT_A_SUBTYPE_ID;
 
     public static class ImeSubtypeListItem implements Comparable<ImeSubtypeListItem> {
+
+        @NonNull
         public final CharSequence mImeName;
+        @Nullable
         public final CharSequence mSubtypeName;
+        @NonNull
         public final InputMethodInfo mImi;
         public final int mSubtypeId;
         public final boolean mIsSystemLocale;
         public final boolean mIsSystemLanguage;
 
-        ImeSubtypeListItem(CharSequence imeName, CharSequence subtypeName,
-                InputMethodInfo imi, int subtypeId, String subtypeLocale, String systemLocale) {
+        ImeSubtypeListItem(@NonNull CharSequence imeName, @Nullable CharSequence subtypeName,
+                @NonNull InputMethodInfo imi, int subtypeId, @Nullable String subtypeLocale,
+                @NonNull String systemLocale) {
             mImeName = imeName;
             mSubtypeName = subtypeName;
             mImi = imi;
@@ -69,7 +74,6 @@
                 if (mIsSystemLocale) {
                     mIsSystemLanguage = true;
                 } else {
-                    // TODO: Use Locale#getLanguage or Locale#toLanguageTag
                     final String systemLanguage = LocaleUtils.getLanguageFromLocaleString(
                             systemLocale);
                     final String subtypeLanguage = LocaleUtils.getLanguageFromLocaleString(
@@ -101,8 +105,9 @@
          *   <li>{@link #mSubtypeName}</li>
          *   <li>{@link #mImi} with {@link InputMethodInfo#getId()}</li>
          * </ol>
-         * Note: this class has a natural ordering that is inconsistent with {@link #equals(Object).
-         * This method doesn't compare {@link #mSubtypeId} but {@link #equals(Object)} does.
+         * Note: this class has a natural ordering that is inconsistent with
+         * {@link #equals(Object)}. This method doesn't compare {@link #mSubtypeId} but
+         * {@link #equals(Object)} does.
          *
          * @param other the object to be compared.
          * @return a negative integer, zero, or positive integer as this object is less than, equal
@@ -155,6 +160,7 @@
         }
     }
 
+    @NonNull
     static List<ImeSubtypeListItem> getSortedInputMethodAndSubtypeList(
             boolean includeAuxiliarySubtypes, boolean isScreenLocked, boolean forImeMenu,
             @NonNull Context context, @NonNull InputMethodMap methodMap,
@@ -190,7 +196,7 @@
                 enabledSubtypeSet.add(String.valueOf(subtype.hashCode()));
             }
             final CharSequence imeLabel = imi.loadLabel(userAwareContext.getPackageManager());
-            if (enabledSubtypeSet.size() > 0) {
+            if (!enabledSubtypeSet.isEmpty()) {
                 final int subtypeCount = imi.getSubtypeCount();
                 if (DEBUG) {
                     Slog.v(TAG, "Add subtypes: " + subtypeCount + ", " + imi.getId());
@@ -223,14 +229,18 @@
         return imList;
     }
 
-    private static int calculateSubtypeId(InputMethodInfo imi, InputMethodSubtype subtype) {
+    private static int calculateSubtypeId(@NonNull InputMethodInfo imi,
+            @Nullable InputMethodSubtype subtype) {
         return subtype != null ? SubtypeUtils.getSubtypeIdFromHashCode(imi, subtype.hashCode())
                 : NOT_A_SUBTYPE_ID;
     }
 
     private static class StaticRotationList {
+
+        @NonNull
         private final List<ImeSubtypeListItem> mImeSubtypeList;
-        StaticRotationList(final List<ImeSubtypeListItem> imeSubtypeList) {
+
+        StaticRotationList(@NonNull List<ImeSubtypeListItem> imeSubtypeList) {
             mImeSubtypeList = imeSubtypeList;
         }
 
@@ -242,24 +252,22 @@
          *                does not have a subtype.
          * @return The index in the given list. -1 if not found.
          */
-        private int getIndex(InputMethodInfo imi, InputMethodSubtype subtype) {
+        private int getIndex(@NonNull InputMethodInfo imi, @Nullable InputMethodSubtype subtype) {
             final int currentSubtypeId = calculateSubtypeId(imi, subtype);
             final int numSubtypes = mImeSubtypeList.size();
             for (int i = 0; i < numSubtypes; ++i) {
-                final ImeSubtypeListItem isli = mImeSubtypeList.get(i);
+                final ImeSubtypeListItem item = mImeSubtypeList.get(i);
                 // Skip until the current IME/subtype is found.
-                if (imi.equals(isli.mImi) && isli.mSubtypeId == currentSubtypeId) {
+                if (imi.equals(item.mImi) && item.mSubtypeId == currentSubtypeId) {
                     return i;
                 }
             }
             return -1;
         }
 
+        @Nullable
         public ImeSubtypeListItem getNextInputMethodLocked(boolean onlyCurrentIme,
-                InputMethodInfo imi, InputMethodSubtype subtype) {
-            if (imi == null) {
-                return null;
-            }
+                @NonNull InputMethodInfo imi, @Nullable InputMethodSubtype subtype) {
             if (mImeSubtypeList.size() <= 1) {
                 return null;
             }
@@ -282,22 +290,24 @@
             return null;
         }
 
-        protected void dump(final Printer pw, final String prefix) {
+        protected void dump(@NonNull Printer pw, @NonNull String prefix) {
             final int numSubtypes = mImeSubtypeList.size();
-            for (int i = 0; i < numSubtypes; ++i) {
-                final int rank = i;
-                final ImeSubtypeListItem item = mImeSubtypeList.get(i);
+            for (int rank = 0; rank < numSubtypes; ++rank) {
+                final ImeSubtypeListItem item = mImeSubtypeList.get(rank);
                 pw.println(prefix + "rank=" + rank + " item=" + item);
             }
         }
     }
 
     private static class DynamicRotationList {
+
         private static final String TAG = DynamicRotationList.class.getSimpleName();
+        @NonNull
         private final List<ImeSubtypeListItem> mImeSubtypeList;
+        @NonNull
         private final int[] mUsageHistoryOfSubtypeListItemIndex;
 
-        private DynamicRotationList(final List<ImeSubtypeListItem> imeSubtypeListItems) {
+        private DynamicRotationList(@NonNull List<ImeSubtypeListItem> imeSubtypeListItems) {
             mImeSubtypeList = imeSubtypeListItems;
             mUsageHistoryOfSubtypeListItemIndex = new int[mImeSubtypeList.size()];
             final int numSubtypes = mImeSubtypeList.size();
@@ -314,7 +324,8 @@
          *
          * @return -1 when the specified item doesn't belong to {@link #mImeSubtypeList} actually.
          */
-        private int getUsageRank(final InputMethodInfo imi, InputMethodSubtype subtype) {
+        private int getUsageRank(@NonNull InputMethodInfo imi,
+                @Nullable InputMethodSubtype subtype) {
             final int currentSubtypeId = calculateSubtypeId(imi, subtype);
             final int numItems = mUsageHistoryOfSubtypeListItemIndex.length;
             for (int usageRank = 0; usageRank < numItems; usageRank++) {
@@ -330,7 +341,8 @@
             return -1;
         }
 
-        public void onUserAction(InputMethodInfo imi, InputMethodSubtype subtype) {
+        public void onUserAction(@NonNull InputMethodInfo imi,
+                @Nullable InputMethodSubtype subtype) {
             final int currentUsageRank = getUsageRank(imi, subtype);
             // Do nothing if currentUsageRank == -1 (not found), or currentUsageRank == 0
             if (currentUsageRank <= 0) {
@@ -342,8 +354,9 @@
             mUsageHistoryOfSubtypeListItemIndex[0] = currentItemIndex;
         }
 
+        @Nullable
         public ImeSubtypeListItem getNextInputMethodLocked(boolean onlyCurrentIme,
-                InputMethodInfo imi, InputMethodSubtype subtype) {
+                @NonNull InputMethodInfo imi, @Nullable InputMethodSubtype subtype) {
             int currentUsageRank = getUsageRank(imi, subtype);
             if (currentUsageRank < 0) {
                 if (DEBUG) {
@@ -366,7 +379,7 @@
             return null;
         }
 
-        protected void dump(final Printer pw, final String prefix) {
+        protected void dump(@NonNull Printer pw, @NonNull String prefix) {
             for (int rank = 0; rank < mUsageHistoryOfSubtypeListItemIndex.length; ++rank) {
                 final int index = mUsageHistoryOfSubtypeListItemIndex[rank];
                 final ImeSubtypeListItem item = mImeSubtypeList.get(index);
@@ -377,58 +390,52 @@
 
     @VisibleForTesting
     public static class ControllerImpl {
+
+        @NonNull
         private final DynamicRotationList mSwitchingAwareRotationList;
+        @NonNull
         private final StaticRotationList mSwitchingUnawareRotationList;
 
-        public static ControllerImpl createFrom(final ControllerImpl currentInstance,
-                final List<ImeSubtypeListItem> sortedEnabledItems) {
-            DynamicRotationList switchingAwareRotationList = null;
-            {
-                final List<ImeSubtypeListItem> switchingAwareImeSubtypes =
-                        filterImeSubtypeList(sortedEnabledItems,
-                                true /* supportsSwitchingToNextInputMethod */);
-                if (currentInstance != null
-                        && currentInstance.mSwitchingAwareRotationList != null
-                        && Objects.equals(
-                                currentInstance.mSwitchingAwareRotationList.mImeSubtypeList,
-                                switchingAwareImeSubtypes)) {
-                    // Can reuse the current instance.
-                    switchingAwareRotationList = currentInstance.mSwitchingAwareRotationList;
-                }
-                if (switchingAwareRotationList == null) {
-                    switchingAwareRotationList = new DynamicRotationList(switchingAwareImeSubtypes);
-                }
+        @NonNull
+        public static ControllerImpl createFrom(@Nullable ControllerImpl currentInstance,
+                @NonNull List<ImeSubtypeListItem> sortedEnabledItems) {
+            final var switchingAwareImeSubtypes = filterImeSubtypeList(sortedEnabledItems,
+                    true /* supportsSwitchingToNextInputMethod */);
+            final var switchingUnawareImeSubtypes = filterImeSubtypeList(sortedEnabledItems,
+                    false /* supportsSwitchingToNextInputMethod */);
+
+            final DynamicRotationList switchingAwareRotationList;
+            if (currentInstance != null && Objects.equals(
+                    currentInstance.mSwitchingAwareRotationList.mImeSubtypeList,
+                    switchingAwareImeSubtypes)) {
+                // Can reuse the current instance.
+                switchingAwareRotationList = currentInstance.mSwitchingAwareRotationList;
+            } else {
+                switchingAwareRotationList = new DynamicRotationList(switchingAwareImeSubtypes);
             }
 
-            StaticRotationList switchingUnawareRotationList = null;
-            {
-                final List<ImeSubtypeListItem> switchingUnawareImeSubtypes = filterImeSubtypeList(
-                        sortedEnabledItems, false /* supportsSwitchingToNextInputMethod */);
-                if (currentInstance != null
-                        && currentInstance.mSwitchingUnawareRotationList != null
-                        && Objects.equals(
-                                currentInstance.mSwitchingUnawareRotationList.mImeSubtypeList,
-                                switchingUnawareImeSubtypes)) {
-                    // Can reuse the current instance.
-                    switchingUnawareRotationList = currentInstance.mSwitchingUnawareRotationList;
-                }
-                if (switchingUnawareRotationList == null) {
-                    switchingUnawareRotationList =
-                            new StaticRotationList(switchingUnawareImeSubtypes);
-                }
+            final StaticRotationList switchingUnawareRotationList;
+            if (currentInstance != null && Objects.equals(
+                    currentInstance.mSwitchingUnawareRotationList.mImeSubtypeList,
+                    switchingUnawareImeSubtypes)) {
+                // Can reuse the current instance.
+                switchingUnawareRotationList = currentInstance.mSwitchingUnawareRotationList;
+            } else {
+                switchingUnawareRotationList = new StaticRotationList(switchingUnawareImeSubtypes);
             }
 
             return new ControllerImpl(switchingAwareRotationList, switchingUnawareRotationList);
         }
 
-        private ControllerImpl(final DynamicRotationList switchingAwareRotationList,
-                final StaticRotationList switchingUnawareRotationList) {
+        private ControllerImpl(@NonNull DynamicRotationList switchingAwareRotationList,
+                @NonNull StaticRotationList switchingUnawareRotationList) {
             mSwitchingAwareRotationList = switchingAwareRotationList;
             mSwitchingUnawareRotationList = switchingUnawareRotationList;
         }
 
-        public ImeSubtypeListItem getNextInputMethod(boolean onlyCurrentIme, InputMethodInfo imi,
-                InputMethodSubtype subtype) {
+        @Nullable
+        public ImeSubtypeListItem getNextInputMethod(boolean onlyCurrentIme,
+                @Nullable InputMethodInfo imi, @Nullable InputMethodSubtype subtype) {
             if (imi == null) {
                 return null;
             }
@@ -441,18 +448,17 @@
             }
         }
 
-        public void onUserActionLocked(InputMethodInfo imi, InputMethodSubtype subtype) {
-            if (imi == null) {
-                return;
-            }
+        public void onUserActionLocked(@NonNull InputMethodInfo imi,
+                @Nullable InputMethodSubtype subtype) {
             if (imi.supportsSwitchingToNextInputMethod()) {
                 mSwitchingAwareRotationList.onUserAction(imi, subtype);
             }
         }
 
+        @NonNull
         private static List<ImeSubtypeListItem> filterImeSubtypeList(
-                final List<ImeSubtypeListItem> items,
-                final boolean supportsSwitchingToNextInputMethod) {
+                @NonNull List<ImeSubtypeListItem> items,
+                boolean supportsSwitchingToNextInputMethod) {
             final ArrayList<ImeSubtypeListItem> result = new ArrayList<>();
             final int numItems = items.size();
             for (int i = 0; i < numItems; i++) {
@@ -473,12 +479,14 @@
         }
     }
 
+    @NonNull
     private final Context mContext;
     @UserIdInt
     private final int mUserId;
+    @NonNull
     private ControllerImpl mController;
 
-    private InputMethodSubtypeSwitchingController(@NonNull Context context,
+    InputMethodSubtypeSwitchingController(@NonNull Context context,
             @NonNull InputMethodMap methodMap, @UserIdInt int userId) {
         mContext = context;
         mUserId = userId;
@@ -488,26 +496,14 @@
                         false /* forImeMenu */, context, methodMap, userId));
     }
 
-    @NonNull
-    public static InputMethodSubtypeSwitchingController createInstanceLocked(
-            @NonNull Context context,
-            @NonNull InputMethodMap methodMap, @UserIdInt int userId) {
-        return new InputMethodSubtypeSwitchingController(context, methodMap, userId);
-    }
-
     @AnyThread
     @UserIdInt
     int getUserId() {
         return mUserId;
     }
 
-    public void onUserActionLocked(InputMethodInfo imi, InputMethodSubtype subtype) {
-        if (mController == null) {
-            if (DEBUG) {
-                Slog.e(TAG, "mController shouldn't be null.");
-            }
-            return;
-        }
+    public void onUserActionLocked(@NonNull InputMethodInfo imi,
+            @Nullable InputMethodSubtype subtype) {
         mController.onUserActionLocked(imi, subtype);
     }
 
@@ -518,22 +514,13 @@
                         false /* forImeMenu */, mContext, methodMap, mUserId));
     }
 
-    public ImeSubtypeListItem getNextInputMethodLocked(boolean onlyCurrentIme, InputMethodInfo imi,
-            InputMethodSubtype subtype) {
-        if (mController == null) {
-            if (DEBUG) {
-                Slog.e(TAG, "mController shouldn't be null.");
-            }
-            return null;
-        }
+    @Nullable
+    public ImeSubtypeListItem getNextInputMethodLocked(boolean onlyCurrentIme,
+            @Nullable InputMethodInfo imi, @Nullable InputMethodSubtype subtype) {
         return mController.getNextInputMethod(onlyCurrentIme, imi, subtype);
     }
 
     public void dump(@NonNull Printer pw, @NonNull String prefix) {
-        if (mController != null) {
-            mController.dump(pw, prefix);
-        } else {
-            pw.println(prefix + "mController=null");
-        }
+        mController.dump(pw, prefix);
     }
 }
diff --git a/services/tests/InputMethodSystemServerTests/src/com/android/server/inputmethod/InputMethodSubtypeSwitchingControllerTest.java b/services/tests/InputMethodSystemServerTests/src/com/android/server/inputmethod/InputMethodSubtypeSwitchingControllerTest.java
index fbe384a..02b7291 100644
--- a/services/tests/InputMethodSystemServerTests/src/com/android/server/inputmethod/InputMethodSubtypeSwitchingControllerTest.java
+++ b/services/tests/InputMethodSystemServerTests/src/com/android/server/inputmethod/InputMethodSubtypeSwitchingControllerTest.java
@@ -18,6 +18,7 @@
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertNotEquals;
 import static org.junit.Assert.assertTrue;
 
 import android.content.ComponentName;
@@ -28,6 +29,9 @@
 import android.view.inputmethod.InputMethodSubtype;
 import android.view.inputmethod.InputMethodSubtype.InputMethodSubtypeBuilder;
 
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+
 import com.android.server.inputmethod.InputMethodSubtypeSwitchingController.ControllerImpl;
 import com.android.server.inputmethod.InputMethodSubtypeSwitchingController.ImeSubtypeListItem;
 
@@ -38,50 +42,51 @@
 import java.util.List;
 
 public final class InputMethodSubtypeSwitchingControllerTest {
-    private static final String DUMMY_PACKAGE_NAME = "dummy package name";
-    private static final String DUMMY_IME_LABEL = "dummy ime label";
-    private static final String DUMMY_SETTING_ACTIVITY_NAME = "";
-    private static final boolean DUMMY_IS_AUX_IME = false;
-    private static final boolean DUMMY_FORCE_DEFAULT = false;
-    private static final boolean DUMMY_IS_VR_IME = false;
-    private static final int DUMMY_IS_DEFAULT_RES_ID = 0;
+    private static final String TEST_PACKAGE_NAME = "test package name";
+    private static final String TEST_IME_LABEL = "test ime label";
+    private static final String TEST_SETTING_ACTIVITY_NAME = "";
+    private static final boolean TEST_IS_AUX_IME = false;
+    private static final boolean TEST_FORCE_DEFAULT = false;
+    private static final boolean TEST_IS_VR_IME = false;
+    private static final int TEST_IS_DEFAULT_RES_ID = 0;
     private static final String SYSTEM_LOCALE = "en_US";
     private static final int NOT_A_SUBTYPE_ID = InputMethodUtils.NOT_A_SUBTYPE_ID;
 
-    private static InputMethodSubtype createDummySubtype(final String locale) {
-        final InputMethodSubtypeBuilder builder = new InputMethodSubtypeBuilder();
-        return builder.setSubtypeNameResId(0)
+    @NonNull
+    private static InputMethodSubtype createTestSubtype(@NonNull String locale) {
+        return new InputMethodSubtypeBuilder()
+                .setSubtypeNameResId(0)
                 .setSubtypeIconResId(0)
                 .setSubtypeLocale(locale)
                 .setIsAsciiCapable(true)
                 .build();
     }
 
-    private static void addDummyImeSubtypeListItems(List<ImeSubtypeListItem> items,
-            String imeName, String imeLabel, List<String> subtypeLocales,
-            boolean supportsSwitchingToNextInputMethod) {
+    private static void addTestImeSubtypeListItems(@NonNull List<ImeSubtypeListItem> items,
+            @NonNull String imeName, @NonNull String imeLabel,
+            @Nullable List<String> subtypeLocales, boolean supportsSwitchingToNextInputMethod) {
         final ResolveInfo ri = new ResolveInfo();
         final ServiceInfo si = new ServiceInfo();
         final ApplicationInfo ai = new ApplicationInfo();
-        ai.packageName = DUMMY_PACKAGE_NAME;
+        ai.packageName = TEST_PACKAGE_NAME;
         ai.enabled = true;
         si.applicationInfo = ai;
         si.enabled = true;
-        si.packageName = DUMMY_PACKAGE_NAME;
+        si.packageName = TEST_PACKAGE_NAME;
         si.name = imeName;
         si.exported = true;
         si.nonLocalizedLabel = imeLabel;
         ri.serviceInfo = si;
         List<InputMethodSubtype> subtypes = null;
         if (subtypeLocales != null) {
-            subtypes = new ArrayList<InputMethodSubtype>();
+            subtypes = new ArrayList<>();
             for (String subtypeLocale : subtypeLocales) {
-                subtypes.add(createDummySubtype(subtypeLocale));
+                subtypes.add(createTestSubtype(subtypeLocale));
             }
         }
-        final InputMethodInfo imi = new InputMethodInfo(ri, DUMMY_IS_AUX_IME,
-                DUMMY_SETTING_ACTIVITY_NAME, subtypes, DUMMY_IS_DEFAULT_RES_ID,
-                DUMMY_FORCE_DEFAULT, supportsSwitchingToNextInputMethod, DUMMY_IS_VR_IME);
+        final InputMethodInfo imi = new InputMethodInfo(ri, TEST_IS_AUX_IME,
+                TEST_SETTING_ACTIVITY_NAME, subtypes, TEST_IS_DEFAULT_RES_ID,
+                TEST_FORCE_DEFAULT, supportsSwitchingToNextInputMethod, TEST_IS_VR_IME);
         if (subtypes == null) {
             items.add(new ImeSubtypeListItem(imeName, null /* variableName */, imi,
                     NOT_A_SUBTYPE_ID, null, SYSTEM_LOCALE));
@@ -94,105 +99,105 @@
         }
     }
 
-    private static ImeSubtypeListItem createDummyItem(ComponentName imeComponentName,
-            String imeName, String subtypeName, String subtypeLocale, int subtypeIndex,
-            String systemLocale) {
-        final ResolveInfo ri = new ResolveInfo();
-        final ServiceInfo si = new ServiceInfo();
-        final ApplicationInfo ai = new ApplicationInfo();
+    @NonNull
+    private static ImeSubtypeListItem createTestItem(@NonNull ComponentName imeComponentName,
+            @NonNull String imeName, @NonNull String subtypeName,
+            @NonNull String subtypeLocale, int subtypeIndex,
+            @NonNull String systemLocale) {
+        final var ai = new ApplicationInfo();
         ai.packageName = imeComponentName.getPackageName();
         ai.enabled = true;
+        final var si = new ServiceInfo();
         si.applicationInfo = ai;
         si.enabled = true;
         si.packageName = imeComponentName.getPackageName();
         si.name = imeComponentName.getClassName();
         si.exported = true;
-        si.nonLocalizedLabel = DUMMY_IME_LABEL;
+        si.nonLocalizedLabel = TEST_IME_LABEL;
+        final var ri = new ResolveInfo();
         ri.serviceInfo = si;
-        ArrayList<InputMethodSubtype> subtypes = new ArrayList<>();
+        final var subtypes = new ArrayList<InputMethodSubtype>();
         subtypes.add(new InputMethodSubtypeBuilder()
                 .setSubtypeNameResId(0)
                 .setSubtypeIconResId(0)
                 .setSubtypeLocale(subtypeLocale)
                 .setIsAsciiCapable(true)
                 .build());
-        final InputMethodInfo imi = new InputMethodInfo(ri, DUMMY_IS_AUX_IME,
-                DUMMY_SETTING_ACTIVITY_NAME, subtypes, DUMMY_IS_DEFAULT_RES_ID,
-                DUMMY_FORCE_DEFAULT, true /* supportsSwitchingToNextInputMethod */,
-                DUMMY_IS_VR_IME);
+        final InputMethodInfo imi = new InputMethodInfo(ri, TEST_IS_AUX_IME,
+                TEST_SETTING_ACTIVITY_NAME, subtypes, TEST_IS_DEFAULT_RES_ID,
+                TEST_FORCE_DEFAULT, true /* supportsSwitchingToNextInputMethod */,
+                TEST_IS_VR_IME);
         return new ImeSubtypeListItem(imeName, subtypeName, imi, subtypeIndex, subtypeLocale,
                 systemLocale);
     }
 
+    @NonNull
     private static List<ImeSubtypeListItem> createEnabledImeSubtypes() {
-        final List<ImeSubtypeListItem> items = new ArrayList<ImeSubtypeListItem>();
-        addDummyImeSubtypeListItems(items, "LatinIme", "LatinIme", Arrays.asList("en_US", "fr"),
+        final var items = new ArrayList<ImeSubtypeListItem>();
+        addTestImeSubtypeListItems(items, "LatinIme", "LatinIme", Arrays.asList("en_US", "fr"),
                 true /* supportsSwitchingToNextInputMethod*/);
-        addDummyImeSubtypeListItems(items, "switchUnawareLatinIme", "switchUnawareLatinIme",
+        addTestImeSubtypeListItems(items, "switchUnawareLatinIme", "switchUnawareLatinIme",
                 Arrays.asList("en_UK", "hi"),
                 false /* supportsSwitchingToNextInputMethod*/);
-        addDummyImeSubtypeListItems(items, "subtypeUnawareIme", "subtypeUnawareIme", null,
+        addTestImeSubtypeListItems(items, "subtypeUnawareIme", "subtypeUnawareIme", null,
                 false /* supportsSwitchingToNextInputMethod*/);
-        addDummyImeSubtypeListItems(items, "JapaneseIme", "JapaneseIme", Arrays.asList("ja_JP"),
+        addTestImeSubtypeListItems(items, "JapaneseIme", "JapaneseIme", Arrays.asList("ja_JP"),
                 true /* supportsSwitchingToNextInputMethod*/);
-        addDummyImeSubtypeListItems(items, "switchUnawareJapaneseIme", "switchUnawareJapaneseIme",
+        addTestImeSubtypeListItems(items, "switchUnawareJapaneseIme", "switchUnawareJapaneseIme",
                 Arrays.asList("ja_JP"), false /* supportsSwitchingToNextInputMethod*/);
         return items;
     }
 
+    @NonNull
     private static List<ImeSubtypeListItem> createDisabledImeSubtypes() {
-        final List<ImeSubtypeListItem> items = new ArrayList<ImeSubtypeListItem>();
-        addDummyImeSubtypeListItems(items,
+        final var items = new ArrayList<ImeSubtypeListItem>();
+        addTestImeSubtypeListItems(items,
                 "UnknownIme", "UnknownIme",
                 Arrays.asList("en_US", "hi"),
                 true /* supportsSwitchingToNextInputMethod*/);
-        addDummyImeSubtypeListItems(items,
+        addTestImeSubtypeListItems(items,
                 "UnknownSwitchingUnawareIme", "UnknownSwitchingUnawareIme",
                 Arrays.asList("en_US"),
                 false /* supportsSwitchingToNextInputMethod*/);
-        addDummyImeSubtypeListItems(items, "UnknownSubtypeUnawareIme",
+        addTestImeSubtypeListItems(items, "UnknownSubtypeUnawareIme",
                 "UnknownSubtypeUnawareIme", null,
                 false /* supportsSwitchingToNextInputMethod*/);
         return items;
     }
 
-    private void assertNextInputMethod(final ControllerImpl controller,
-            final boolean onlyCurrentIme,
-            final ImeSubtypeListItem currentItem, final ImeSubtypeListItem nextItem) {
+    private void assertNextInputMethod(@NonNull ControllerImpl controller, boolean onlyCurrentIme,
+            @NonNull ImeSubtypeListItem currentItem, @Nullable ImeSubtypeListItem nextItem) {
         InputMethodSubtype subtype = null;
         if (currentItem.mSubtypeName != null) {
-            subtype = createDummySubtype(currentItem.mSubtypeName.toString());
+            subtype = createTestSubtype(currentItem.mSubtypeName.toString());
         }
         final ImeSubtypeListItem nextIme = controller.getNextInputMethod(onlyCurrentIme,
                 currentItem.mImi, subtype);
         assertEquals(nextItem, nextIme);
     }
 
-    private void assertRotationOrder(final ControllerImpl controller,
-            final boolean onlyCurrentIme,
-            final ImeSubtypeListItem... expectedRotationOrderOfImeSubtypeList) {
+    private void assertRotationOrder(@NonNull ControllerImpl controller, boolean onlyCurrentIme,
+            ImeSubtypeListItem... expectedRotationOrderOfImeSubtypeList) {
         final int numItems = expectedRotationOrderOfImeSubtypeList.length;
         for (int i = 0; i < numItems; i++) {
-            final int currentIndex = i;
-            final int nextIndex = (currentIndex + 1) % numItems;
-            final ImeSubtypeListItem currentItem =
-                    expectedRotationOrderOfImeSubtypeList[currentIndex];
+            final int nextIndex = (i + 1) % numItems;
+            final ImeSubtypeListItem currentItem = expectedRotationOrderOfImeSubtypeList[i];
             final ImeSubtypeListItem nextItem = expectedRotationOrderOfImeSubtypeList[nextIndex];
             assertNextInputMethod(controller, onlyCurrentIme, currentItem, nextItem);
         }
     }
 
-    private void onUserAction(final ControllerImpl controller,
-            final ImeSubtypeListItem subtypeListItem) {
+    private void onUserAction(@NonNull ControllerImpl controller,
+            @NonNull ImeSubtypeListItem subtypeListItem) {
         InputMethodSubtype subtype = null;
         if (subtypeListItem.mSubtypeName != null) {
-            subtype = createDummySubtype(subtypeListItem.mSubtypeName.toString());
+            subtype = createTestSubtype(subtypeListItem.mSubtypeName.toString());
         }
         controller.onUserActionLocked(subtypeListItem.mImi, subtype);
     }
 
     @Test
-    public void testControllerImpl() throws Exception {
+    public void testControllerImpl() {
         final List<ImeSubtypeListItem> disabledItems = createDisabledImeSubtypes();
         final ImeSubtypeListItem disabledIme_en_us = disabledItems.get(0);
         final ImeSubtypeListItem disabledIme_hi = disabledItems.get(1);
@@ -252,7 +257,7 @@
     }
 
     @Test
-    public void testControllerImplWithUserAction() throws Exception {
+    public void testControllerImplWithUserAction() {
         final List<ImeSubtypeListItem> enabledItems = createEnabledImeSubtypes();
         final ImeSubtypeListItem latinIme_en_us = enabledItems.get(0);
         final ImeSubtypeListItem latinIme_fr = enabledItems.get(1);
@@ -333,22 +338,23 @@
     }
 
     @Test
-    public void testImeSubtypeListItem() throws Exception {
-        final List<ImeSubtypeListItem> items = new ArrayList<ImeSubtypeListItem>();
-        addDummyImeSubtypeListItems(items, "LatinIme", "LatinIme",
+    public void testImeSubtypeListItem() {
+        final var items = new ArrayList<ImeSubtypeListItem>();
+        addTestImeSubtypeListItems(items, "LatinIme", "LatinIme",
                 Arrays.asList("en_US", "fr", "en", "en_uk", "enn", "e", "EN_US"),
                 true /* supportsSwitchingToNextInputMethod*/);
         final ImeSubtypeListItem item_en_us = items.get(0);
         final ImeSubtypeListItem item_fr = items.get(1);
         final ImeSubtypeListItem item_en = items.get(2);
-        final ImeSubtypeListItem item_enn = items.get(3);
-        final ImeSubtypeListItem item_e = items.get(4);
-        final ImeSubtypeListItem item_en_us_allcaps = items.get(5);
+        final ImeSubtypeListItem item_en_uk = items.get(3);
+        final ImeSubtypeListItem item_enn = items.get(4);
+        final ImeSubtypeListItem item_e = items.get(5);
+        final ImeSubtypeListItem item_en_us_allcaps = items.get(6);
 
         assertTrue(item_en_us.mIsSystemLocale);
         assertFalse(item_fr.mIsSystemLocale);
         assertFalse(item_en.mIsSystemLocale);
-        assertFalse(item_en.mIsSystemLocale);
+        assertFalse(item_en_uk.mIsSystemLocale);
         assertFalse(item_enn.mIsSystemLocale);
         assertFalse(item_e.mIsSystemLocale);
         assertFalse(item_en_us_allcaps.mIsSystemLocale);
@@ -356,14 +362,15 @@
         assertTrue(item_en_us.mIsSystemLanguage);
         assertFalse(item_fr.mIsSystemLanguage);
         assertTrue(item_en.mIsSystemLanguage);
-        assertFalse(item_enn.mIsSystemLocale);
-        assertFalse(item_e.mIsSystemLocale);
-        assertFalse(item_en_us_allcaps.mIsSystemLocale);
+        assertTrue(item_en_uk.mIsSystemLanguage);
+        assertFalse(item_enn.mIsSystemLanguage);
+        assertFalse(item_e.mIsSystemLanguage);
+        assertFalse(item_en_us_allcaps.mIsSystemLanguage);
     }
 
     @SuppressWarnings("SelfComparison")
     @Test
-    public void testImeSubtypeListComparator() throws Exception {
+    public void testImeSubtypeListComparator() {
         final ComponentName imeX1 = new ComponentName("com.example.imeX", "Ime1");
         final ComponentName imeX2 = new ComponentName("com.example.imeX", "Ime2");
         final ComponentName imeY1 = new ComponentName("com.example.imeY", "Ime1");
@@ -372,64 +379,64 @@
             final List<ImeSubtypeListItem> items = Arrays.asList(
                     // Subtypes of two IMEs that have the same display name "X".
                     // Subtypes that has the same locale of the system's.
-                    createDummyItem(imeX1, "X", "E", "en_US", 0, "en_US"),
-                    createDummyItem(imeX2, "X", "E", "en_US", 0, "en_US"),
-                    createDummyItem(imeX1, "X", "Z", "en_US", 3, "en_US"),
-                    createDummyItem(imeX2, "X", "Z", "en_US", 3, "en_US"),
-                    createDummyItem(imeX1, "X", "", "en_US", 6, "en_US"),
-                    createDummyItem(imeX2, "X", "", "en_US", 6, "en_US"),
+                    createTestItem(imeX1, "X", "E", "en_US", 0, "en_US"),
+                    createTestItem(imeX2, "X", "E", "en_US", 0, "en_US"),
+                    createTestItem(imeX1, "X", "Z", "en_US", 3, "en_US"),
+                    createTestItem(imeX2, "X", "Z", "en_US", 3, "en_US"),
+                    createTestItem(imeX1, "X", "", "en_US", 6, "en_US"),
+                    createTestItem(imeX2, "X", "", "en_US", 6, "en_US"),
                     // Subtypes that has the same language of the system's.
-                    createDummyItem(imeX1, "X", "E", "en", 1, "en_US"),
-                    createDummyItem(imeX2, "X", "E", "en", 1, "en_US"),
-                    createDummyItem(imeX1, "X", "Z", "en", 4, "en_US"),
-                    createDummyItem(imeX2, "X", "Z", "en", 4, "en_US"),
-                    createDummyItem(imeX1, "X", "", "en", 7, "en_US"),
-                    createDummyItem(imeX2, "X", "", "en", 7, "en_US"),
+                    createTestItem(imeX1, "X", "E", "en", 1, "en_US"),
+                    createTestItem(imeX2, "X", "E", "en", 1, "en_US"),
+                    createTestItem(imeX1, "X", "Z", "en", 4, "en_US"),
+                    createTestItem(imeX2, "X", "Z", "en", 4, "en_US"),
+                    createTestItem(imeX1, "X", "", "en", 7, "en_US"),
+                    createTestItem(imeX2, "X", "", "en", 7, "en_US"),
                     // Subtypes that has different language than the system's.
-                    createDummyItem(imeX1, "X", "A", "hi_IN", 27, "en_US"),
-                    createDummyItem(imeX2, "X", "A", "hi_IN", 27, "en_US"),
-                    createDummyItem(imeX1, "X", "E", "ja", 2, "en_US"),
-                    createDummyItem(imeX2, "X", "E", "ja", 2, "en_US"),
-                    createDummyItem(imeX1, "X", "Z", "ja", 5, "en_US"),
-                    createDummyItem(imeX2, "X", "Z", "ja", 5, "en_US"),
-                    createDummyItem(imeX1, "X", "", "ja", 8, "en_US"),
-                    createDummyItem(imeX2, "X", "", "ja", 8, "en_US"),
+                    createTestItem(imeX1, "X", "A", "hi_IN", 27, "en_US"),
+                    createTestItem(imeX2, "X", "A", "hi_IN", 27, "en_US"),
+                    createTestItem(imeX1, "X", "E", "ja", 2, "en_US"),
+                    createTestItem(imeX2, "X", "E", "ja", 2, "en_US"),
+                    createTestItem(imeX1, "X", "Z", "ja", 5, "en_US"),
+                    createTestItem(imeX2, "X", "Z", "ja", 5, "en_US"),
+                    createTestItem(imeX1, "X", "", "ja", 8, "en_US"),
+                    createTestItem(imeX2, "X", "", "ja", 8, "en_US"),
 
                     // Subtypes of IME "Y".
                     // Subtypes that has the same locale of the system's.
-                    createDummyItem(imeY1, "Y", "E", "en_US", 9, "en_US"),
-                    createDummyItem(imeY1, "Y", "Z", "en_US", 12, "en_US"),
-                    createDummyItem(imeY1, "Y", "", "en_US", 15, "en_US"),
+                    createTestItem(imeY1, "Y", "E", "en_US", 9, "en_US"),
+                    createTestItem(imeY1, "Y", "Z", "en_US", 12, "en_US"),
+                    createTestItem(imeY1, "Y", "", "en_US", 15, "en_US"),
                     // Subtypes that has the same language of the system's.
-                    createDummyItem(imeY1, "Y", "E", "en", 10, "en_US"),
-                    createDummyItem(imeY1, "Y", "Z", "en", 13, "en_US"),
-                    createDummyItem(imeY1, "Y", "", "en", 16, "en_US"),
+                    createTestItem(imeY1, "Y", "E", "en", 10, "en_US"),
+                    createTestItem(imeY1, "Y", "Z", "en", 13, "en_US"),
+                    createTestItem(imeY1, "Y", "", "en", 16, "en_US"),
                     // Subtypes that has different language than the system's.
-                    createDummyItem(imeY1, "Y", "A", "hi_IN", 28, "en_US"),
-                    createDummyItem(imeY1, "Y", "E", "ja", 11, "en_US"),
-                    createDummyItem(imeY1, "Y", "Z", "ja", 14, "en_US"),
-                    createDummyItem(imeY1, "Y", "", "ja", 17, "en_US"),
+                    createTestItem(imeY1, "Y", "A", "hi_IN", 28, "en_US"),
+                    createTestItem(imeY1, "Y", "E", "ja", 11, "en_US"),
+                    createTestItem(imeY1, "Y", "Z", "ja", 14, "en_US"),
+                    createTestItem(imeY1, "Y", "", "ja", 17, "en_US"),
 
                     // Subtypes of IME Z.
                     // Subtypes that has the same locale of the system's.
-                    createDummyItem(imeZ1, "", "E", "en_US", 18, "en_US"),
-                    createDummyItem(imeZ1, "", "Z", "en_US", 21, "en_US"),
-                    createDummyItem(imeZ1, "", "", "en_US", 24, "en_US"),
+                    createTestItem(imeZ1, "", "E", "en_US", 18, "en_US"),
+                    createTestItem(imeZ1, "", "Z", "en_US", 21, "en_US"),
+                    createTestItem(imeZ1, "", "", "en_US", 24, "en_US"),
                     // Subtypes that has the same language of the system's.
-                    createDummyItem(imeZ1, "", "E", "en", 19, "en_US"),
-                    createDummyItem(imeZ1, "", "Z", "en", 22, "en_US"),
-                    createDummyItem(imeZ1, "", "", "en", 25, "en_US"),
+                    createTestItem(imeZ1, "", "E", "en", 19, "en_US"),
+                    createTestItem(imeZ1, "", "Z", "en", 22, "en_US"),
+                    createTestItem(imeZ1, "", "", "en", 25, "en_US"),
                     // Subtypes that has different language than the system's.
-                    createDummyItem(imeZ1, "", "A", "hi_IN", 29, "en_US"),
-                    createDummyItem(imeZ1, "", "E", "ja", 20, "en_US"),
-                    createDummyItem(imeZ1, "", "Z", "ja", 23, "en_US"),
-                    createDummyItem(imeZ1, "", "", "ja", 26, "en_US"));
+                    createTestItem(imeZ1, "", "A", "hi_IN", 29, "en_US"),
+                    createTestItem(imeZ1, "", "E", "ja", 20, "en_US"),
+                    createTestItem(imeZ1, "", "Z", "ja", 23, "en_US"),
+                    createTestItem(imeZ1, "", "", "ja", 26, "en_US"));
 
             // Ensure {@link java.lang.Comparable#compareTo} contracts are satisfied.
             for (int i = 0; i < items.size(); ++i) {
                 final ImeSubtypeListItem item1 = items.get(i);
                 // Ensures sgn(x.compareTo(y)) == -sgn(y.compareTo(x)).
-                assertTrue(item1 + " has the same order of itself", item1.compareTo(item1) == 0);
+                assertEquals(item1 + " has the same order of itself", 0, item1.compareTo(item1));
                 // Ensures (x.compareTo(y) > 0 && y.compareTo(z) > 0) implies x.compareTo(z) > 0.
                 for (int j = i + 1; j < items.size(); ++j) {
                     final ImeSubtypeListItem item2 = items.get(j);
@@ -443,25 +450,25 @@
         {
             // Following two items have the same priority.
             final ImeSubtypeListItem nonSystemLocale1 =
-                    createDummyItem(imeX1, "X", "A", "ja_JP", 0, "en_US");
+                    createTestItem(imeX1, "X", "A", "ja_JP", 0, "en_US");
             final ImeSubtypeListItem nonSystemLocale2 =
-                    createDummyItem(imeX1, "X", "A", "hi_IN", 1, "en_US");
-            assertTrue(nonSystemLocale1.compareTo(nonSystemLocale2) == 0);
-            assertTrue(nonSystemLocale2.compareTo(nonSystemLocale1) == 0);
+                    createTestItem(imeX1, "X", "A", "hi_IN", 1, "en_US");
+            assertEquals(0, nonSystemLocale1.compareTo(nonSystemLocale2));
+            assertEquals(0, nonSystemLocale2.compareTo(nonSystemLocale1));
             // But those aren't equal to each other.
-            assertFalse(nonSystemLocale1.equals(nonSystemLocale2));
-            assertFalse(nonSystemLocale2.equals(nonSystemLocale1));
+            assertNotEquals(nonSystemLocale1, nonSystemLocale2);
+            assertNotEquals(nonSystemLocale2, nonSystemLocale1);
         }
 
         {
             // Check if ComponentName is also taken into account when comparing two items.
-            final ImeSubtypeListItem ime1 = createDummyItem(imeX1, "X", "A", "ja_JP", 0, "en_US");
-            final ImeSubtypeListItem ime2 = createDummyItem(imeX2, "X", "A", "ja_JP", 0, "en_US");
+            final ImeSubtypeListItem ime1 = createTestItem(imeX1, "X", "A", "ja_JP", 0, "en_US");
+            final ImeSubtypeListItem ime2 = createTestItem(imeX2, "X", "A", "ja_JP", 0, "en_US");
             assertTrue(ime1.compareTo(ime2) < 0);
             assertTrue(ime2.compareTo(ime1) > 0);
             // But those aren't equal to each other.
-            assertFalse(ime1.equals(ime2));
-            assertFalse(ime2.equals(ime1));
+            assertNotEquals(ime1, ime2);
+            assertNotEquals(ime2, ime1);
         }
     }
 }