diff --git a/java/src/com/android/inputmethod/latin/ResizableIntArray.java b/java/src/com/android/inputmethod/latin/ResizableIntArray.java
index 6feae9c5a..387d45a53 100644
--- a/java/src/com/android/inputmethod/latin/ResizableIntArray.java
+++ b/java/src/com/android/inputmethod/latin/ResizableIntArray.java
@@ -28,38 +28,49 @@ public class ResizableIntArray {
     }
 
     public int get(final int index) {
-        if (index < 0 || index >= mLength) {
-            throw new ArrayIndexOutOfBoundsException("length=" + mLength + "; index=" + index);
+        if (index < mLength) {
+            return mArray[index];
         }
-        return mArray[index];
+        throw new ArrayIndexOutOfBoundsException("length=" + mLength + "; index=" + index);
     }
 
     public void add(final int index, final int val) {
-        if (mLength < index + 1) {
+        if (index < mLength) {
+            mArray[index] = val;
+        } else {
             mLength = index;
             add(val);
-        } else {
-            mArray[index] = val;
         }
     }
 
     public void add(final int val) {
-        final int nextLength = mLength + 1;
-        ensureCapacity(nextLength);
-        mArray[mLength] = val;
-        mLength = nextLength;
+        final int currentLength = mLength;
+        ensureCapacity(currentLength + 1);
+        mArray[currentLength] = val;
+        mLength = currentLength + 1;
+    }
+
+    /**
+     * Calculate the new capacity of {@code mArray}.
+     * @param minimumCapacity the minimum capacity that the {@code mArray} should have.
+     * @return the new capacity that the {@code mArray} should have. Returns zero when there is no
+     * need to expand {@code mArray}.
+     */
+    private int calculateCapacity(final int minimumCapacity) {
+        final int currentCapcity = mArray.length;
+        if (currentCapcity < minimumCapacity) {
+            final int nextCapacity = currentCapcity * 2;
+            // The following is the same as return Math.max(minimumCapacity, nextCapacity);
+            return minimumCapacity > nextCapacity ? minimumCapacity : nextCapacity;
+        }
+        return 0;
     }
 
     private void ensureCapacity(final int minimumCapacity) {
-        if (mArray.length < minimumCapacity) {
-            final int nextCapacity = mArray.length * 2;
-            // The following is the same as newLength =
-            // Math.max(minimumCapacity, nextCapacity);
-            final int newLength = minimumCapacity > nextCapacity
-                    ? minimumCapacity
-                    : nextCapacity;
+        final int newCapacity = calculateCapacity(minimumCapacity);
+        if (newCapacity > 0) {
             // TODO: Implement primitive array pool.
-            mArray = Arrays.copyOf(mArray, newLength);
+            mArray = Arrays.copyOf(mArray, newCapacity);
         }
     }
 
@@ -89,17 +100,35 @@ public class ResizableIntArray {
     }
 
     public void copy(final ResizableIntArray ip) {
-        // TODO: Avoid useless coping of values.
-        ensureCapacity(ip.mLength);
+        final int newCapacity = calculateCapacity(ip.mLength);
+        if (newCapacity > 0) {
+            // TODO: Implement primitive array pool.
+            mArray = new int[newCapacity];
+        }
         System.arraycopy(ip.mArray, 0, mArray, 0, ip.mLength);
         mLength = ip.mLength;
     }
 
     public void append(final ResizableIntArray src, final int startPos, final int length) {
+        if (length == 0) {
+            return;
+        }
         final int currentLength = mLength;
         final int newLength = currentLength + length;
         ensureCapacity(newLength);
         System.arraycopy(src.mArray, startPos, mArray, currentLength, length);
         mLength = newLength;
     }
+
+    public void fill(final int value, final int startPos, final int length) {
+        if (startPos < 0 || length < 0) {
+            throw new IllegalArgumentException("startPos=" + startPos + "; length=" + length);
+        }
+        final int endPos = startPos + length;
+        ensureCapacity(endPos);
+        Arrays.fill(mArray, startPos, endPos, value);
+        if (mLength < endPos) {
+            mLength = endPos;
+        }
+    }
 }
diff --git a/tests/src/com/android/inputmethod/latin/ResizableIntArrayTests.java b/tests/src/com/android/inputmethod/latin/ResizableIntArrayTests.java
index 80e5f9cb1..995fc14ea 100644
--- a/tests/src/com/android/inputmethod/latin/ResizableIntArrayTests.java
+++ b/tests/src/com/android/inputmethod/latin/ResizableIntArrayTests.java
@@ -37,8 +37,12 @@ public class ResizableIntArrayTests extends AndroidTestCase {
         for (int i = 0; i < limit; i++) {
             src.add(i);
             assertEquals("length after add " + i, i + 1, src.getLength());
-            if (i == DEFAULT_CAPACITY) array2 = src.getPrimitiveArray();
-            if (i == DEFAULT_CAPACITY * 2) array3 = src.getPrimitiveArray();
+            if (i == DEFAULT_CAPACITY) {
+                array2 = src.getPrimitiveArray();
+            }
+            if (i == DEFAULT_CAPACITY * 2) {
+                array3 = src.getPrimitiveArray();
+            }
             if (i < DEFAULT_CAPACITY) {
                 assertSame("array after add " + i, array, src.getPrimitiveArray());
             } else if (i < DEFAULT_CAPACITY * 2) {
@@ -110,7 +114,9 @@ public class ResizableIntArrayTests extends AndroidTestCase {
         for (int i = 0; i < DEFAULT_CAPACITY; i++) {
             src.add(i);
             assertEquals("length after add " + i, i + 1, src.getLength());
-            if (i == smallerLength) array3 = src.getPrimitiveArray();
+            if (i == smallerLength) {
+                array3 = src.getPrimitiveArray();
+            }
             if (i < smallerLength) {
                 assertSame("array after add " + i, array2, src.getPrimitiveArray());
             } else if (i < smallerLength * 2) {
@@ -133,11 +139,13 @@ public class ResizableIntArrayTests extends AndroidTestCase {
         assertEquals("length after larger setLength", largerLength, src.getLength());
         assertNotSame("array after larger setLength", array, array2);
         assertEquals("array length after larger setLength", largerLength, array2.length);
-        for (int i = 0; i < DEFAULT_CAPACITY; i++) {
-            assertEquals("value at " + i, i, src.get(i));
-        }
-        for (int i = DEFAULT_CAPACITY; i < largerLength; i++) {
-            assertEquals("value at " + i, 0, src.get(i));
+        for (int i = 0; i < largerLength; i++) {
+            final int v = src.get(i);
+            if (i < DEFAULT_CAPACITY) {
+                assertEquals("value at " + i, i, v);
+            } else {
+                assertEquals("value at " + i, 0, v);
+            }
         }
 
         final int smallerLength = DEFAULT_CAPACITY / 2;
@@ -236,6 +244,79 @@ public class ResizableIntArrayTests extends AndroidTestCase {
                 src.getPrimitiveArray(), 0, dst.getPrimitiveArray(), dstLen + srcLen, srcLen);
     }
 
+    public void testFill() {
+        final int srcLen = DEFAULT_CAPACITY;
+        final ResizableIntArray src = new ResizableIntArray(srcLen);
+        for (int i = 0; i < srcLen; i++) {
+            src.add(i);
+        }
+        final int[] array = src.getPrimitiveArray();
+
+        final int startPos = srcLen / 3;
+        final int length = srcLen / 3;
+        final int endPos = startPos + length;
+        assertTrue(startPos >= 1);
+        final int value = 123;
+        try {
+            src.fill(value, -1, length);
+            fail("fill from -1 shouldn't succeed");
+        } catch (IllegalArgumentException e) {
+            // success
+        }
+        try {
+            src.fill(value, startPos, -1);
+            fail("fill negative length shouldn't succeed");
+        } catch (IllegalArgumentException e) {
+            // success
+        }
+
+        src.fill(value, startPos, length);
+        assertEquals("length after fill", srcLen, src.getLength());
+        assertSame("array after fill", array, src.getPrimitiveArray());
+        for (int i = 0; i < srcLen; i++) {
+            final int v = src.get(i);
+            if (i >= startPos && i < endPos) {
+                assertEquals("new values after fill at " + i, value, v);
+            } else {
+                assertEquals("unmodified values after fill at " + i, i, v);
+            }
+        }
+
+        final int length2 = srcLen * 2 - startPos;
+        final int largeEnd = startPos + length2;
+        assertTrue(largeEnd > srcLen);
+        final int value2 = 456;
+        src.fill(value2, startPos, length2);
+        assertEquals("length after large fill", largeEnd, src.getLength());
+        assertNotSame("array after large fill", array, src.getPrimitiveArray());
+        for (int i = 0; i < largeEnd; i++) {
+            final int v = src.get(i);
+            if (i >= startPos && i < largeEnd) {
+                assertEquals("new values after large fill at " + i, value2, v);
+            } else {
+                assertEquals("unmodified values after large fill at " + i, i, v);
+            }
+        }
+
+        final int startPos2 = largeEnd + length2;
+        final int endPos2 = startPos2 + length2;
+        final int value3 = 789;
+        src.fill(value3, startPos2, length2);
+        assertEquals("length after disjoint fill", endPos2, src.getLength());
+        for (int i = 0; i < endPos2; i++) {
+            final int v = src.get(i);
+            if (i >= startPos2 && i < endPos2) {
+                assertEquals("new values after disjoint fill at " + i, value3, v);
+            } else if (i >= startPos && i < largeEnd) {
+                assertEquals("unmodified values after disjoint fill at " + i, value2, v);
+            } else if (i < startPos) {
+                assertEquals("unmodified values after disjoint fill at " + i, i, v);
+            } else {
+                assertEquals("gap values after disjoint fill at " + i, 0, v);
+            }
+        }
+    }
+
     private static void assertArrayEquals(String message, int[] expecteds, int expectedPos,
             int[] actuals, int actualPos, int length) {
         if (expecteds == null && actuals == null) {