diff --git a/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java b/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java
index 2539313..0fa2cf4 100644
--- a/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java
+++ b/java/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtils.java
@@ -546,7 +546,7 @@
             throws FileNotFoundException, IOException, UnsupportedFormatException {
         final byte[] buffer = new byte[HEADER_READING_BUFFER_SIZE];
         final Ver3DictDecoder dictDecoder = new Ver3DictDecoder(file);
-        dictDecoder.openDictBuffer(new Ver3DictDecoder.DictionaryBufferFactory() {
+        dictDecoder.openDictBuffer(new DictDecoder.DictionaryBufferFactory() {
             @Override
             public DictBuffer getDictionaryBuffer(File file)
                     throws FileNotFoundException, IOException {
diff --git a/java/src/com/android/inputmethod/latin/makedict/DictDecoder.java b/java/src/com/android/inputmethod/latin/makedict/DictDecoder.java
new file mode 100644
index 0000000..a63d9d5
--- /dev/null
+++ b/java/src/com/android/inputmethod/latin/makedict/DictDecoder.java
@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.inputmethod.latin.makedict;
+
+import com.android.inputmethod.annotations.UsedForTesting;
+import com.android.inputmethod.latin.makedict.BinaryDictDecoderUtils.DictBuffer;
+import com.android.inputmethod.latin.makedict.FormatSpec.FileHeader;
+import com.android.inputmethod.latin.utils.ByteArrayDictBuffer;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.io.RandomAccessFile;
+import java.nio.ByteBuffer;
+import java.nio.channels.FileChannel;
+
+/**
+ * An interface of binary dictionary decoder.
+ */
+public interface DictDecoder {
+    public FileHeader readHeader() throws IOException, UnsupportedFormatException;
+
+    public interface DictionaryBufferFactory {
+        public DictBuffer getDictionaryBuffer(final File file)
+                throws FileNotFoundException, IOException;
+    }
+
+    /**
+     * Creates DictionaryBuffer using a ByteBuffer
+     *
+     * This class uses less memory than DictionaryBufferFromByteArrayFactory,
+     * but doesn't perform as fast.
+     * When operating on a big dictionary, this class is preferred.
+     */
+    public static final class DictionaryBufferFromReadOnlyByteBufferFactory
+            implements DictionaryBufferFactory {
+        @Override
+        public DictBuffer getDictionaryBuffer(final File file)
+                throws FileNotFoundException, IOException {
+            FileInputStream inStream = null;
+            ByteBuffer buffer = null;
+            try {
+                inStream = new FileInputStream(file);
+                buffer = inStream.getChannel().map(FileChannel.MapMode.READ_ONLY,
+                        0, file.length());
+            } finally {
+                if (inStream != null) {
+                    inStream.close();
+                }
+            }
+            if (buffer != null) {
+                return new BinaryDictDecoderUtils.ByteBufferDictBuffer(buffer);
+            }
+            return null;
+        }
+    }
+
+    /**
+     * Creates DictionaryBuffer using a byte array
+     *
+     * This class performs faster than other classes, but consumes more memory.
+     * When operating on a small dictionary, this class is preferred.
+     */
+    public static final class DictionaryBufferFromByteArrayFactory
+            implements DictionaryBufferFactory {
+        @Override
+        public DictBuffer getDictionaryBuffer(final File file)
+                throws FileNotFoundException, IOException {
+            FileInputStream inStream = null;
+            try {
+                inStream = new FileInputStream(file);
+                final byte[] array = new byte[(int) file.length()];
+                inStream.read(array);
+                return new ByteArrayDictBuffer(array);
+            } finally {
+                if (inStream != null) {
+                    inStream.close();
+                }
+            }
+        }
+    }
+
+    /**
+     * Creates DictionaryBuffer using a writable ByteBuffer and a RandomAccessFile.
+     *
+     * This class doesn't perform as fast as other classes,
+     * but this class is the only option available for destructive operations (insert or delete)
+     * on a dictionary.
+     */
+    @UsedForTesting
+    public static final class DictionaryBufferFromWritableByteBufferFactory
+            implements DictionaryBufferFactory {
+        @Override
+        public DictBuffer getDictionaryBuffer(final File file)
+                throws FileNotFoundException, IOException {
+            RandomAccessFile raFile = null;
+            ByteBuffer buffer = null;
+            try {
+                raFile = new RandomAccessFile(file, "rw");
+                buffer = raFile.getChannel().map(FileChannel.MapMode.READ_WRITE, 0, file.length());
+            } finally {
+                if (raFile != null) {
+                    raFile.close();
+                }
+            }
+            if (buffer != null) {
+                return new BinaryDictDecoderUtils.ByteBufferDictBuffer(buffer);
+            }
+            return null;
+        }
+    }
+}
diff --git a/java/src/com/android/inputmethod/latin/makedict/Ver3DictDecoder.java b/java/src/com/android/inputmethod/latin/makedict/Ver3DictDecoder.java
index 7c18c8c..7a9323c 100644
--- a/java/src/com/android/inputmethod/latin/makedict/Ver3DictDecoder.java
+++ b/java/src/com/android/inputmethod/latin/makedict/Ver3DictDecoder.java
@@ -21,21 +21,18 @@
 import com.android.inputmethod.latin.makedict.BinaryDictDecoderUtils.DictBuffer;
 import com.android.inputmethod.latin.makedict.FormatSpec.FileHeader;
 import com.android.inputmethod.latin.makedict.FormatSpec.FormatOptions;
-import com.android.inputmethod.latin.utils.ByteArrayDictBuffer;
 import com.android.inputmethod.latin.utils.JniUtils;
 
 import java.io.File;
-import java.io.FileInputStream;
 import java.io.FileNotFoundException;
 import java.io.IOException;
-import java.io.RandomAccessFile;
-import java.nio.ByteBuffer;
-import java.nio.channels.FileChannel;
 import java.util.HashMap;
 
-// TODO: Make an interface "DictDecoder".
+/**
+ * An implementation of DictDecoder for version 3 binary dictionary.
+ */
 @UsedForTesting
-public class Ver3DictDecoder {
+public class Ver3DictDecoder implements DictDecoder {
 
     static {
         JniUtils.loadNativeLibrary();
@@ -44,96 +41,6 @@
     // TODO: implement something sensical instead of just a phony method
     private static native int doNothing();
 
-    public interface DictionaryBufferFactory {
-        public DictBuffer getDictionaryBuffer(final File file)
-                throws FileNotFoundException, IOException;
-    }
-
-    /**
-     * Creates DictionaryBuffer using a ByteBuffer
-     *
-     * This class uses less memory than DictionaryBufferFromByteArrayFactory,
-     * but doesn't perform as fast.
-     * When operating on a big dictionary, this class is preferred.
-     */
-    public static final class DictionaryBufferFromReadOnlyByteBufferFactory
-            implements DictionaryBufferFactory {
-        @Override
-        public DictBuffer getDictionaryBuffer(final File file)
-                throws FileNotFoundException, IOException {
-            FileInputStream inStream = null;
-            ByteBuffer buffer = null;
-            try {
-                inStream = new FileInputStream(file);
-                buffer = inStream.getChannel().map(FileChannel.MapMode.READ_ONLY,
-                        0, file.length());
-            } finally {
-                if (inStream != null) {
-                    inStream.close();
-                }
-            }
-            if (buffer != null) {
-                return new BinaryDictDecoderUtils.ByteBufferDictBuffer(buffer);
-            }
-            return null;
-        }
-    }
-
-    /**
-     * Creates DictionaryBuffer using a byte array
-     *
-     * This class performs faster than other classes, but consumes more memory.
-     * When operating on a small dictionary, this class is preferred.
-     */
-    public static final class DictionaryBufferFromByteArrayFactory
-            implements DictionaryBufferFactory {
-        @Override
-        public DictBuffer getDictionaryBuffer(final File file)
-                throws FileNotFoundException, IOException {
-            FileInputStream inStream = null;
-            try {
-                inStream = new FileInputStream(file);
-                final byte[] array = new byte[(int) file.length()];
-                inStream.read(array);
-                return new ByteArrayDictBuffer(array);
-            } finally {
-                if (inStream != null) {
-                    inStream.close();
-                }
-            }
-        }
-    }
-
-    /**
-     * Creates DictionaryBuffer using a writable ByteBuffer and a RandomAccessFile.
-     *
-     * This class doesn't perform as fast as other classes,
-     * but this class is the only option available for destructive operations (insert or delete)
-     * on a dictionary.
-     */
-    @UsedForTesting
-    public static final class DictionaryBufferFromWritableByteBufferFactory
-            implements DictionaryBufferFactory {
-        @Override
-        public DictBuffer getDictionaryBuffer(final File file)
-                throws FileNotFoundException, IOException {
-            RandomAccessFile raFile = null;
-            ByteBuffer buffer = null;
-            try {
-                raFile = new RandomAccessFile(file, "rw");
-                buffer = raFile.getChannel().map(FileChannel.MapMode.READ_WRITE, 0, file.length());
-            } finally {
-                if (raFile != null) {
-                    raFile.close();
-                }
-            }
-            if (buffer != null) {
-                return new BinaryDictDecoderUtils.ByteBufferDictBuffer(buffer);
-            }
-            return null;
-        }
-    }
-
     private final static class HeaderReader {
         protected static int readVersion(final DictBuffer dictBuffer)
                 throws IOException, UnsupportedFormatException {
@@ -171,7 +78,7 @@
         mDictBuffer = null;
     }
 
-    public void openDictBuffer(final DictionaryBufferFactory factory)
+    public void openDictBuffer(final DictDecoder.DictionaryBufferFactory factory)
             throws FileNotFoundException, IOException {
         mDictBuffer = factory.getDictionaryBuffer(mDictionaryBinaryFile);
     }
@@ -181,14 +88,13 @@
     }
 
     @UsedForTesting
-    public DictBuffer openAndGetDictBuffer(
-            final DictionaryBufferFactory factory)
+    public DictBuffer openAndGetDictBuffer(final DictDecoder.DictionaryBufferFactory factory)
                     throws FileNotFoundException, IOException {
         openDictBuffer(factory);
         return getDictBuffer();
     }
 
-    // TODO : Define public functions of decoders
+    @Override
     public FileHeader readHeader() throws IOException, UnsupportedFormatException {
         final int version = HeaderReader.readVersion(mDictBuffer);
         final int optionsFlags = HeaderReader.readOptionFlags(mDictBuffer);
diff --git a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtilsTests.java b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtilsTests.java
index f0ad58f..74c20a3 100644
--- a/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtilsTests.java
+++ b/tests/src/com/android/inputmethod/latin/makedict/BinaryDictIOUtilsTests.java
@@ -22,12 +22,12 @@
 import android.util.Log;
 
 import com.android.inputmethod.latin.makedict.BinaryDictDecoderUtils.DictBuffer;
+import com.android.inputmethod.latin.makedict.DictDecoder.
+        DictionaryBufferFromWritableByteBufferFactory;
 import com.android.inputmethod.latin.makedict.FormatSpec.FileHeader;
 import com.android.inputmethod.latin.makedict.FusionDictionary.PtNodeArray;
 import com.android.inputmethod.latin.makedict.FusionDictionary.WeightedString;
 import com.android.inputmethod.latin.utils.CollectionUtils;
-import com.android.inputmethod.latin.makedict.Ver3DictDecoder.
-        DictionaryBufferFromWritableByteBufferFactory;
 
 import java.io.BufferedOutputStream;
 import java.io.File;
diff --git a/tests/src/com/android/inputmethod/latin/makedict/Ver3DictDecoderTests.java b/tests/src/com/android/inputmethod/latin/makedict/Ver3DictDecoderTests.java
index 43c9b91..20e8b4f 100644
--- a/tests/src/com/android/inputmethod/latin/makedict/Ver3DictDecoderTests.java
+++ b/tests/src/com/android/inputmethod/latin/makedict/Ver3DictDecoderTests.java
@@ -17,12 +17,11 @@
 package com.android.inputmethod.latin.makedict;
 
 import com.android.inputmethod.latin.makedict.BinaryDictDecoderUtils.DictBuffer;
-import com.android.inputmethod.latin.makedict.Ver3DictDecoder.DictionaryBufferFactory;
-import com.android.inputmethod.latin.makedict.Ver3DictDecoder.
-        DictionaryBufferFromByteArrayFactory;
-import com.android.inputmethod.latin.makedict.Ver3DictDecoder.
+import com.android.inputmethod.latin.makedict.DictDecoder.DictionaryBufferFactory;
+import com.android.inputmethod.latin.makedict.DictDecoder.DictionaryBufferFromByteArrayFactory;
+import com.android.inputmethod.latin.makedict.DictDecoder.
         DictionaryBufferFromReadOnlyByteBufferFactory;
-import com.android.inputmethod.latin.makedict.Ver3DictDecoder.
+import com.android.inputmethod.latin.makedict.DictDecoder.
         DictionaryBufferFromWritableByteBufferFactory;
 
 import android.test.AndroidTestCase;
@@ -60,8 +59,7 @@
     }
 
     @SuppressWarnings("null")
-    public void runTestOpenBuffer(final String testName,
-            final DictionaryBufferFactory factory) {
+    public void runTestOpenBuffer(final String testName, final DictionaryBufferFactory factory) {
         File testFile = null;
         try {
             testFile = File.createTempFile(testName, ".tmp", getContext().getCacheDir());
@@ -104,8 +102,7 @@
     }
 
     @SuppressWarnings("null")
-    public void runTestGetBuffer(final String testName,
-            final DictionaryBufferFactory factory) {
+    public void runTestGetBuffer(final String testName, final DictionaryBufferFactory factory) {
         File testFile = null;
         try {
             testFile = File.createTempFile(testName, ".tmp", getContext().getCacheDir());