diff --git a/java/src/com/android/inputmethod/keyboard/Keyboard.java b/java/src/com/android/inputmethod/keyboard/Keyboard.java
index 3abe890..9198500 100644
--- a/java/src/com/android/inputmethod/keyboard/Keyboard.java
+++ b/java/src/com/android/inputmethod/keyboard/Keyboard.java
@@ -219,6 +219,11 @@
         return code >= CODE_SPACE;
     }
 
+    @Override
+    public String toString() {
+        return mId.toString();
+    }
+
     public static class Params {
         public KeyboardId mId;
         public int mThemeId;
diff --git a/java/src/com/android/inputmethod/keyboard/PointerTracker.java b/java/src/com/android/inputmethod/keyboard/PointerTracker.java
index 184011f..2b90a3c 100644
--- a/java/src/com/android/inputmethod/keyboard/PointerTracker.java
+++ b/java/src/com/android/inputmethod/keyboard/PointerTracker.java
@@ -34,7 +34,7 @@
 
 import java.util.ArrayList;
 
-public class PointerTracker implements PointerTrackerQueue.ElementActions {
+public class PointerTracker implements PointerTrackerQueue.Element {
     private static final String TAG = PointerTracker.class.getSimpleName();
     private static final boolean DEBUG_EVENT = false;
     private static final boolean DEBUG_MOVE_EVENT = false;
diff --git a/java/src/com/android/inputmethod/keyboard/internal/PointerTrackerQueue.java b/java/src/com/android/inputmethod/keyboard/internal/PointerTrackerQueue.java
index bd16480..1c7ceaf 100644
--- a/java/src/com/android/inputmethod/keyboard/internal/PointerTrackerQueue.java
+++ b/java/src/com/android/inputmethod/keyboard/internal/PointerTrackerQueue.java
@@ -18,85 +18,146 @@
 
 import android.util.Log;
 
-import java.util.Iterator;
-import java.util.LinkedList;
+import java.util.ArrayList;
 
 public class PointerTrackerQueue {
     private static final String TAG = PointerTrackerQueue.class.getSimpleName();
     private static final boolean DEBUG = false;
 
-    public interface ElementActions {
+    public interface Element {
         public boolean isModifier();
         public boolean isInSlidingKeyInput();
         public void onPhantomUpEvent(long eventTime);
     }
 
-    // TODO: Use ring buffer instead of {@link LinkedList}.
-    private final LinkedList<ElementActions> mQueue = new LinkedList<ElementActions>();
+    private static final int INITIAL_CAPACITY = 10;
+    private final ArrayList<Element> mExpandableArrayOfActivePointers =
+            new ArrayList<Element>(INITIAL_CAPACITY);
+    private int mArraySize = 0;
 
-    public int size() {
-        return mQueue.size();
+    public synchronized int size() {
+        return mArraySize;
     }
 
-    public synchronized void add(ElementActions tracker) {
-        mQueue.add(tracker);
+    public synchronized void add(final Element pointer) {
+        final ArrayList<Element> expandableArray = mExpandableArrayOfActivePointers;
+        final int arraySize = mArraySize;
+        if (arraySize < expandableArray.size()) {
+            expandableArray.set(arraySize, pointer);
+        } else {
+            expandableArray.add(pointer);
+        }
+        mArraySize = arraySize + 1;
     }
 
-    public synchronized void remove(ElementActions tracker) {
-        mQueue.remove(tracker);
+    public synchronized void remove(final Element pointer) {
+        final ArrayList<Element> expandableArray = mExpandableArrayOfActivePointers;
+        final int arraySize = mArraySize;
+        int newSize = 0;
+        for (int index = 0; index < arraySize; index++) {
+            final Element element = expandableArray.get(index);
+            if (element == pointer) {
+                if (newSize != index) {
+                    Log.w(TAG, "Found duplicated element in remove: " + pointer);
+                }
+                continue; // Remove this element from the expandableArray.
+            }
+            if (newSize != index) {
+                // Shift this element toward the beginning of the expandableArray.
+                expandableArray.set(newSize, element);
+            }
+            newSize++;
+        }
+        mArraySize = newSize;
     }
 
-    public synchronized void releaseAllPointersOlderThan(ElementActions tracker,
-            long eventTime) {
+    public synchronized void releaseAllPointersOlderThan(final Element pointer,
+            final long eventTime) {
         if (DEBUG) {
-            Log.d(TAG, "releaseAllPoniterOlderThan: " + tracker + " " + this);
+            Log.d(TAG, "releaseAllPoniterOlderThan: " + pointer + " " + this);
         }
-        if (!mQueue.contains(tracker)) {
-            return;
-        }
-        final Iterator<ElementActions> it = mQueue.iterator();
-        while (it.hasNext()) {
-            final ElementActions t = it.next();
-            if (t == tracker) {
-                break;
+        final ArrayList<Element> expandableArray = mExpandableArrayOfActivePointers;
+        final int arraySize = mArraySize;
+        int newSize, index;
+        for (newSize = index = 0; index < arraySize; index++) {
+            final Element element = expandableArray.get(index);
+            if (element == pointer) {
+                break; // Stop releasing elements.
             }
-            if (!t.isModifier()) {
-                t.onPhantomUpEvent(eventTime);
-                it.remove();
+            if (!element.isModifier()) {
+                element.onPhantomUpEvent(eventTime);
+                continue; // Remove this element from the expandableArray.
+            }
+            if (newSize != index) {
+                // Shift this element toward the beginning of the expandableArray.
+                expandableArray.set(newSize, element);
+            }
+            newSize++;
+        }
+        // Shift rest of the expandableArray.
+        int count = 0;
+        for (; index < arraySize; index++) {
+            final Element element = expandableArray.get(index);
+            if (element == pointer) {
+                if (count > 0) {
+                    Log.w(TAG, "Found duplicated element in releaseAllPointersOlderThan: "
+                            + pointer);
+                }
+                count++;
+            }
+            if (newSize != index) {
+                expandableArray.set(newSize, expandableArray.get(index));
+                newSize++;
             }
         }
+        mArraySize = newSize;
     }
 
-    public void releaseAllPointers(long eventTime) {
+    public void releaseAllPointers(final long eventTime) {
         releaseAllPointersExcept(null, eventTime);
     }
 
-    public synchronized void releaseAllPointersExcept(ElementActions tracker, long eventTime) {
+    public synchronized void releaseAllPointersExcept(final Element pointer,
+            final long eventTime) {
         if (DEBUG) {
-            if (tracker == null) {
+            if (pointer == null) {
                 Log.d(TAG, "releaseAllPoniters: " + this);
             } else {
-                Log.d(TAG, "releaseAllPoniterExcept: " + tracker + " " + this);
+                Log.d(TAG, "releaseAllPoniterExcept: " + pointer + " " + this);
             }
         }
-        final Iterator<ElementActions> it = mQueue.iterator();
-        while (it.hasNext()) {
-            final ElementActions t = it.next();
-            if (t != tracker) {
-                t.onPhantomUpEvent(eventTime);
-                it.remove();
+        final ArrayList<Element> expandableArray = mExpandableArrayOfActivePointers;
+        final int arraySize = mArraySize;
+        int newSize = 0, count = 0;
+        for (int index = 0; index < arraySize; index++) {
+            final Element element = expandableArray.get(index);
+            if (element == pointer) {
+                if (count > 0) {
+                    Log.w(TAG, "Found duplicated element in releaseAllPointersExcept: " + pointer);
+                }
+                count++;
+            } else {
+                element.onPhantomUpEvent(eventTime);
+                continue; // Remove this element from the expandableArray.
             }
+            if (newSize != index) {
+                // Shift this element toward the beginning of the expandableArray.
+                expandableArray.set(newSize, element);
+            }
+            newSize++;
         }
+        mArraySize = newSize;
     }
 
-    public synchronized boolean hasModifierKeyOlderThan(ElementActions tracker) {
-        final Iterator<ElementActions> it = mQueue.iterator();
-        while (it.hasNext()) {
-            final ElementActions t = it.next();
-            if (t == tracker) {
-                break;
+    public synchronized boolean hasModifierKeyOlderThan(final Element pointer) {
+        final ArrayList<Element> expandableArray = mExpandableArrayOfActivePointers;
+        final int arraySize = mArraySize;
+        for (int index = 0; index < arraySize; index++) {
+            final Element element = expandableArray.get(index);
+            if (element == pointer) {
+                return false; // Stop searching modifier key.
             }
-            if (t.isModifier()) {
+            if (element.isModifier()) {
                 return true;
             }
         }
@@ -104,8 +165,11 @@
     }
 
     public synchronized boolean isAnyInSlidingKeyInput() {
-        for (final ElementActions tracker : mQueue) {
-            if (tracker.isInSlidingKeyInput()) {
+        final ArrayList<Element> expandableArray = mExpandableArrayOfActivePointers;
+        final int arraySize = mArraySize;
+        for (int index = 0; index < arraySize; index++) {
+            final Element element = expandableArray.get(index);
+            if (element.isInSlidingKeyInput()) {
                 return true;
             }
         }
@@ -113,12 +177,15 @@
     }
 
     @Override
-    public String toString() {
+    public synchronized String toString() {
         final StringBuilder sb = new StringBuilder();
-        for (final ElementActions tracker : mQueue) {
+        final ArrayList<Element> expandableArray = mExpandableArrayOfActivePointers;
+        final int arraySize = mArraySize;
+        for (int index = 0; index < arraySize; index++) {
+            final Element element = expandableArray.get(index);
             if (sb.length() > 0)
                 sb.append(" ");
-            sb.append(tracker.toString());
+            sb.append(element.toString());
         }
         return "[" + sb.toString() + "]";
     }
diff --git a/java/src/com/android/inputmethod/latin/LatinIME.java b/java/src/com/android/inputmethod/latin/LatinIME.java
index 4550860..43901ba 100644
--- a/java/src/com/android/inputmethod/latin/LatinIME.java
+++ b/java/src/com/android/inputmethod/latin/LatinIME.java
@@ -517,7 +517,7 @@
 
     /* package private */ void resetSuggestMainDict() {
         final Locale subtypeLocale = mSubtypeSwitcher.getCurrentSubtypeLocale();
-        mSuggest.resetMainDict(this, subtypeLocale);
+        mSuggest.resetMainDict(this, subtypeLocale, this /* SuggestInitializationListener */);
         mIsMainDictionaryAvailable = DictionaryFactory.isDictionaryAvailable(this, subtypeLocale);
     }
 
diff --git a/java/src/com/android/inputmethod/latin/Suggest.java b/java/src/com/android/inputmethod/latin/Suggest.java
index 5e2a041..a65d36a 100644
--- a/java/src/com/android/inputmethod/latin/Suggest.java
+++ b/java/src/com/android/inputmethod/latin/Suggest.java
@@ -60,13 +60,11 @@
 
     // Locale used for upper- and title-casing words
     private final Locale mLocale;
-    private final SuggestInitializationListener mListener;
 
     public Suggest(final Context context, final Locale locale,
             final SuggestInitializationListener listener) {
-        initAsynchronously(context, locale);
+        initAsynchronously(context, locale, listener);
         mLocale = locale;
-        mListener = listener;
     }
 
     /* package for test */ Suggest(final Context context, final File dictionary,
@@ -74,7 +72,6 @@
         final Dictionary mainDict = DictionaryFactory.createDictionaryForTest(context, dictionary,
                 startOffset, length /* useFullEditDistance */, false, locale);
         mLocale = locale;
-        mListener = null;
         mMainDictionary = mainDict;
         addOrReplaceDictionary(mDictionaries, Dictionary.TYPE_MAIN, mainDict);
         initWhitelistAndAutocorrectAndPool(context, locale);
@@ -85,8 +82,9 @@
         addOrReplaceDictionary(mDictionaries, Dictionary.TYPE_WHITELIST, mWhiteListDictionary);
     }
 
-    private void initAsynchronously(final Context context, final Locale locale) {
-        resetMainDict(context, locale);
+    private void initAsynchronously(final Context context, final Locale locale,
+            final SuggestInitializationListener listener) {
+        resetMainDict(context, locale, listener);
 
         // TODO: read the whitelist and init the pool asynchronously too.
         // initPool should be done asynchronously now that the pool is thread-safe.
@@ -104,10 +102,11 @@
         }
     }
 
-    public void resetMainDict(final Context context, final Locale locale) {
+    public void resetMainDict(final Context context, final Locale locale,
+            final SuggestInitializationListener listener) {
         mMainDictionary = null;
-        if (mListener != null) {
-            mListener.onUpdateMainDictionaryAvailability(hasMainDictionary());
+        if (listener != null) {
+            listener.onUpdateMainDictionaryAvailability(hasMainDictionary());
         }
         new Thread("InitializeBinaryDictionary") {
             @Override
@@ -116,8 +115,8 @@
                         DictionaryFactory.createMainDictionaryFromManager(context, locale);
                 addOrReplaceDictionary(mDictionaries, Dictionary.TYPE_MAIN, newMainDict);
                 mMainDictionary = newMainDict;
-                if (mListener != null) {
-                    mListener.onUpdateMainDictionaryAvailability(hasMainDictionary());
+                if (listener != null) {
+                    listener.onUpdateMainDictionaryAvailability(hasMainDictionary());
                 }
             }
         }.start();
diff --git a/native/jni/com_android_inputmethod_keyboard_ProximityInfo.cpp b/native/jni/com_android_inputmethod_keyboard_ProximityInfo.cpp
index 74390cc..0f2c2da 100644
--- a/native/jni/com_android_inputmethod_keyboard_ProximityInfo.cpp
+++ b/native/jni/com_android_inputmethod_keyboard_ProximityInfo.cpp
@@ -16,8 +16,6 @@
 
 #define LOG_TAG "LatinIME: jni: ProximityInfo"
 
-#include <string>
-
 #include "com_android_inputmethod_keyboard_ProximityInfo.h"
 #include "jni.h"
 #include "jni_common.h"
@@ -26,14 +24,13 @@
 namespace latinime {
 
 static jlong latinime_Keyboard_setProximityInfo(JNIEnv *env, jobject object,
-        jstring localejStr, jint maxProximityCharsSize, jint displayWidth, jint displayHeight,
+        jstring localeJStr, jint maxProximityCharsSize, jint displayWidth, jint displayHeight,
         jint gridWidth, jint gridHeight, jint mostCommonkeyWidth, jintArray proximityCharsArray,
         jint keyCount, jintArray keyXCoordinateArray, jintArray keyYCoordinateArray,
         jintArray keyWidthArray, jintArray keyHeightArray, jintArray keyCharCodeArray,
         jfloatArray sweetSpotCenterXArray, jfloatArray sweetSpotCenterYArray,
         jfloatArray sweetSpotRadiusArray) {
-    const char *localeStrPtr = env->GetStringUTFChars(localejStr, 0);
-    const std::string localeStr(localeStrPtr);
+    const char *localeCStr = env->GetStringUTFChars(localeJStr, 0);
     jint *proximityChars = env->GetIntArrayElements(proximityCharsArray, 0);
     jint *keyXCoordinates = safeGetIntArrayElements(env, keyXCoordinateArray);
     jint *keyYCoordinates = safeGetIntArrayElements(env, keyYCoordinateArray);
@@ -44,7 +41,7 @@
     jfloat *sweetSpotCenterYs = safeGetFloatArrayElements(env, sweetSpotCenterYArray);
     jfloat *sweetSpotRadii = safeGetFloatArrayElements(env, sweetSpotRadiusArray);
     ProximityInfo *proximityInfo = new ProximityInfo(
-            localeStr, maxProximityCharsSize, displayWidth, displayHeight, gridWidth, gridHeight,
+            localeCStr, maxProximityCharsSize, displayWidth, displayHeight, gridWidth, gridHeight,
             mostCommonkeyWidth, (const int32_t*)proximityChars, keyCount,
             (const int32_t*)keyXCoordinates, (const int32_t*)keyYCoordinates,
             (const int32_t*)keyWidths, (const int32_t*)keyHeights, (const int32_t*)keyCharCodes,
@@ -59,7 +56,7 @@
     safeReleaseIntArrayElements(env, keyYCoordinateArray, keyYCoordinates);
     safeReleaseIntArrayElements(env, keyXCoordinateArray, keyXCoordinates);
     env->ReleaseIntArrayElements(proximityCharsArray, proximityChars, 0);
-    env->ReleaseStringUTFChars(localejStr, localeStrPtr);
+    env->ReleaseStringUTFChars(localeJStr, localeCStr);
     return (jlong)proximityInfo;
 }
 
diff --git a/native/jni/jni_common.cpp b/native/jni/jni_common.cpp
index 105a4dc..d45f97a 100644
--- a/native/jni/jni_common.cpp
+++ b/native/jni/jni_common.cpp
@@ -16,6 +16,8 @@
 
 #define LOG_TAG "LatinIME: jni"
 
+#include <cassert>
+
 #include "com_android_inputmethod_keyboard_ProximityInfo.h"
 #include "com_android_inputmethod_latin_BinaryDictionary.h"
 #include "com_android_inputmethod_latin_NativeUtils.h"
@@ -23,8 +25,6 @@
 #include "jni.h"
 #include "jni_common.h"
 
-#include <cassert>
-
 using namespace latinime;
 
 /*
diff --git a/native/jni/src/proximity_info.cpp b/native/jni/src/proximity_info.cpp
index cee408d..e9cb14e 100644
--- a/native/jni/src/proximity_info.cpp
+++ b/native/jni/src/proximity_info.cpp
@@ -36,7 +36,7 @@
     }
 }
 
-ProximityInfo::ProximityInfo(const std::string localeStr, const int maxProximityCharsSize,
+ProximityInfo::ProximityInfo(const char *localeCStr, const int maxProximityCharsSize,
         const int keyboardWidth, const int keyboardHeight, const int gridWidth,
         const int gridHeight, const int mostCommonKeyWidth,
         const int32_t *proximityCharsArray, const int keyCount, const int32_t *keyXCoordinates,
@@ -52,7 +52,7 @@
           HAS_TOUCH_POSITION_CORRECTION_DATA(keyCount > 0 && keyXCoordinates && keyYCoordinates
                   && keyWidths && keyHeights && keyCharCodes && sweetSpotCenterXs
                   && sweetSpotCenterYs && sweetSpotRadii),
-          mLocaleStr(localeStr) {
+          mLocaleStr(localeCStr) {
     const int proximityGridLength = GRID_WIDTH * GRID_HEIGHT * MAX_PROXIMITY_CHARS_SIZE;
     if (DEBUG_PROXIMITY_INFO) {
         AKLOGI("Create proximity info array %d", proximityGridLength);
diff --git a/native/jni/src/proximity_info.h b/native/jni/src/proximity_info.h
index abd07dd..6c5c6bf 100644
--- a/native/jni/src/proximity_info.h
+++ b/native/jni/src/proximity_info.h
@@ -28,7 +28,7 @@
 
 class ProximityInfo {
  public:
-    ProximityInfo(const std::string localeStr, const int maxProximityCharsSize,
+    ProximityInfo(const char *localeCStr, const int maxProximityCharsSize,
             const int keyboardWidth, const int keyboardHeight, const int gridWidth,
             const int gridHeight, const int mostCommonkeyWidth,
             const int32_t *proximityCharsArray, const int keyCount, const int32_t *keyXCoordinates,
diff --git a/tests/src/com/android/inputmethod/keyboard/internal/PointerTrackerQueueTests.java b/tests/src/com/android/inputmethod/keyboard/internal/PointerTrackerQueueTests.java
index 99fbc96..8fed28f 100644
--- a/tests/src/com/android/inputmethod/keyboard/internal/PointerTrackerQueueTests.java
+++ b/tests/src/com/android/inputmethod/keyboard/internal/PointerTrackerQueueTests.java
@@ -19,7 +19,7 @@
 import android.test.AndroidTestCase;
 
 public class PointerTrackerQueueTests extends AndroidTestCase {
-    public static class Element implements PointerTrackerQueue.ElementActions {
+    public static class Element implements PointerTrackerQueue.Element {
         public static int sPhantomUpCount;
         public static final long NOT_HAPPENED = -1;