diff --git a/java/src/com/android/inputmethod/compat/EditorInfoCompatUtils.java b/java/src/com/android/inputmethod/compat/EditorInfoCompatUtils.java
index d1af7a527..08c246f8b 100644
--- a/java/src/com/android/inputmethod/compat/EditorInfoCompatUtils.java
+++ b/java/src/com/android/inputmethod/compat/EditorInfoCompatUtils.java
@@ -21,12 +21,16 @@ import android.view.inputmethod.EditorInfo;
 import java.lang.reflect.Field;
 
 public class EditorInfoCompatUtils {
+    // EditorInfo.IME_FLAG_FORCE_ASCII has been introduced since API#16 (JellyBean).
     private static final Field FIELD_IME_FLAG_FORCE_ASCII = CompatUtils.getField(
             EditorInfo.class, "IME_FLAG_FORCE_ASCII");
     private static final Integer OBJ_IME_FLAG_FORCE_ASCII = (Integer) CompatUtils
             .getFieldValue(null, null, FIELD_IME_FLAG_FORCE_ASCII);
 
-    // EditorInfo.IME_FLAG_FORCE_ASCII has been introduced since API#16 (JellyBean).
+    private EditorInfoCompatUtils() {
+        // This utility class is not publicly instantiable.
+    }
+
     public static boolean hasFlagForceAscii(int imeOptions) {
         if (OBJ_IME_FLAG_FORCE_ASCII == null)
             return false;
diff --git a/java/src/com/android/inputmethod/compat/InputMethodManagerCompatWrapper.java b/java/src/com/android/inputmethod/compat/InputMethodManagerCompatWrapper.java
index 7be95a095..ffed8202d 100644
--- a/java/src/com/android/inputmethod/compat/InputMethodManagerCompatWrapper.java
+++ b/java/src/com/android/inputmethod/compat/InputMethodManagerCompatWrapper.java
@@ -40,6 +40,10 @@ public class InputMethodManagerCompatWrapper {
 
     private InputMethodManager mImm;
 
+    private InputMethodManagerCompatWrapper() {
+        // This wrapper class is not publicly instantiable.
+    }
+
     public static InputMethodManagerCompatWrapper getInstance() {
         if (sInstance.mImm == null)
             Log.w(TAG, "getInstance() is called before initialization");
diff --git a/java/src/com/android/inputmethod/compat/SuggestionSpanUtils.java b/java/src/com/android/inputmethod/compat/SuggestionSpanUtils.java
index df55aee94..5c351e41f 100644
--- a/java/src/com/android/inputmethod/compat/SuggestionSpanUtils.java
+++ b/java/src/com/android/inputmethod/compat/SuggestionSpanUtils.java
@@ -77,6 +77,10 @@ public class SuggestionSpanUtils {
         }
     }
 
+    private SuggestionSpanUtils() {
+        // This utility class is not publicly instantiable.
+    }
+
     public static CharSequence getTextWithAutoCorrectionIndicatorUnderline(
             Context context, CharSequence text) {
         if (TextUtils.isEmpty(text) || CONSTRUCTOR_SuggestionSpan == null
diff --git a/java/src/com/android/inputmethod/compat/SuggestionsInfoCompatUtils.java b/java/src/com/android/inputmethod/compat/SuggestionsInfoCompatUtils.java
index 723ec2862..e5f9db27c 100644
--- a/java/src/com/android/inputmethod/compat/SuggestionsInfoCompatUtils.java
+++ b/java/src/com/android/inputmethod/compat/SuggestionsInfoCompatUtils.java
@@ -30,6 +30,7 @@ public class SuggestionsInfoCompatUtils {
                     ? OBJ_RESULT_ATTR_HAS_RECOMMENDED_SUGGESTIONS : 0;
 
     private SuggestionsInfoCompatUtils() {
+        // This utility class is not publicly instantiable.
     }
 
     /**