diff --git a/java/src/com/android/inputmethod/latin/InputPointers.java b/java/src/com/android/inputmethod/latin/InputPointers.java
index cd53bcd..5ad5348 100644
--- a/java/src/com/android/inputmethod/latin/InputPointers.java
+++ b/java/src/com/android/inputmethod/latin/InputPointers.java
@@ -16,6 +16,9 @@
 
 package com.android.inputmethod.latin;
 
+import java.util.Arrays;
+
+// TODO: This class is not thread-safe.
 public class InputPointers {
     private final ScalableIntArray mXCoordinates = new ScalableIntArray();
     private final ScalableIntArray mYCoordinates = new ScalableIntArray();
@@ -52,21 +55,15 @@
 
     /**
      * Append the pointers in the specified {@link InputPointers} to the end of this.
-     * @param src the source {@link InputPointers} to append the pointers.
+     * @param src the source {@link InputPointers} to read the data from.
      * @param startPos the starting index of the pointers in {@code src}.
      * @param length the number of pointers to be appended.
      */
     public void append(InputPointers src, int startPos, int length) {
-        final int currentLength = getPointerSize();
-        final int newLength = currentLength + length;
-        mXCoordinates.ensureCapacity(newLength);
-        mYCoordinates.ensureCapacity(newLength);
-        mPointerIds.ensureCapacity(newLength);
-        mTimes.ensureCapacity(newLength);
-        System.arraycopy(src.getXCoordinates(), startPos, getXCoordinates(), currentLength, length);
-        System.arraycopy(src.getYCoordinates(), startPos, getYCoordinates(), currentLength, length);
-        System.arraycopy(src.getPointerIds(), startPos, getPointerIds(), currentLength, length);
-        System.arraycopy(src.getTimes(), startPos, getTimes(), currentLength, length);
+        mXCoordinates.append(src.mXCoordinates, startPos, length);
+        mYCoordinates.append(src.mYCoordinates, startPos, length);
+        mPointerIds.append(src.mPointerIds, startPos, length);
+        mTimes.append(src.mTimes, startPos, length);
     }
 
     public void reset() {
@@ -121,19 +118,17 @@
             mLength = nextLength;
         }
 
-        public void ensureCapacity(int minimumCapacity) {
+        private void ensureCapacity(int minimumCapacity) {
             if (mArray.length < minimumCapacity) {
                 final int nextCapacity = mArray.length * 2;
-                grow(minimumCapacity > nextCapacity ? minimumCapacity : nextCapacity);
+                // The following is the same as newLength = Math.max(minimumCapacity, nextCapacity);
+                final int newLength = minimumCapacity > nextCapacity
+                        ? minimumCapacity
+                        : nextCapacity;
+                mArray = Arrays.copyOf(mArray, newLength);
             }
         }
 
-        private void grow(int newCapacity) {
-            final int[] newArray = new int[newCapacity];
-            System.arraycopy(mArray, 0, newArray, 0, mArray.length);
-            mArray = newArray;
-        }
-
         public int getLength() {
             return mLength;
         }
@@ -147,15 +142,23 @@
             return mArray;
         }
 
+        public void set(ScalableIntArray ip) {
+            mArray = ip.mArray;
+            mLength = ip.mLength;
+        }
+
         public void copy(ScalableIntArray ip) {
             ensureCapacity(ip.mLength);
             System.arraycopy(ip.mArray, 0, mArray, 0, ip.mLength);
             mLength = ip.mLength;
         }
 
-        public void set(ScalableIntArray ip) {
-            mArray = ip.mArray;
-            mLength = ip.mLength;
+        public void append(ScalableIntArray src, int startPos, int length) {
+            final int currentLength = mLength;
+            final int newLength = currentLength + length;
+            ensureCapacity(newLength);
+            System.arraycopy(src.mArray, startPos, mArray, currentLength, length);
+            mLength = newLength;
         }
     }
 }
diff --git a/tests/src/com/android/inputmethod/latin/InputPointersTests.java b/tests/src/com/android/inputmethod/latin/InputPointersTests.java
index b60c2df..524921e 100644
--- a/tests/src/com/android/inputmethod/latin/InputPointersTests.java
+++ b/tests/src/com/android/inputmethod/latin/InputPointersTests.java
@@ -114,47 +114,50 @@
 
     public void testAppend() {
         final InputPointers src = new InputPointers();
-        final int limit = 100;
-        for (int i = 0; i < limit; i++) {
+        final int srcLen = 100;
+        for (int i = 0; i < srcLen; i++) {
             src.addPointer(i, i * 2, i * 3, i * 4);
         }
+        final int dstLen = 50;
         final InputPointers dst = new InputPointers();
-        for (int i = 0; i < limit; i++) {
-            final int value = limit - i;
+        for (int i = 0; i < dstLen; i++) {
+            final int value = -i - 1;
             dst.addPointer(value * 4, value * 3, value * 2, value);
         }
         final InputPointers dstCopy = new InputPointers();
         dstCopy.copy(dst);
 
         dst.append(src, 0, 0);
-        assertEquals("after append zero size", limit, dst.getPointerSize());
-        assertArrayEquals("affer append zero xCoordinates", dstCopy.getXCoordinates(), 0,
-                dst.getXCoordinates(), 0, limit);
-        assertArrayEquals("affer append zero yCoordinates", dstCopy.getYCoordinates(), 0,
-                dst.getYCoordinates(), 0, limit);
-        assertArrayEquals("affer append zero pointerIds", dstCopy.getPointerIds(), 0,
-                dst.getPointerIds(), 0, limit);
-        assertArrayEquals("affer append zero times", dstCopy.getTimes(), 0,
-                dst.getTimes(), 0, limit);
+        assertEquals("after append zero size", dstLen, dst.getPointerSize());
+        assertArrayEquals("after append zero xCoordinates", dstCopy.getXCoordinates(), 0,
+                dst.getXCoordinates(), 0, dstLen);
+        assertArrayEquals("after append zero yCoordinates", dstCopy.getYCoordinates(), 0,
+                dst.getYCoordinates(), 0, dstLen);
+        assertArrayEquals("after append zero pointerIds", dstCopy.getPointerIds(), 0,
+                dst.getPointerIds(), 0, dstLen);
+        assertArrayEquals("after append zero times", dstCopy.getTimes(), 0,
+                dst.getTimes(), 0, dstLen);
 
-        dst.append(src, 0, src.getPointerSize());
-        assertEquals("after append size", limit * 2, dst.getPointerSize() + src.getPointerSize());
-        assertArrayEquals("affer append xCoordinates", dstCopy.getXCoordinates(), 0,
-                dst.getXCoordinates(), 0, limit);
-        assertArrayEquals("affer append yCoordinates", dstCopy.getYCoordinates(), 0,
-                dst.getYCoordinates(), 0, limit);
-        assertArrayEquals("affer append pointerIds", dstCopy.getPointerIds(), 0,
-                dst.getPointerIds(), 0, limit);
-        assertArrayEquals("affer append times", dstCopy.getTimes(), 0,
-                dst.getTimes(), 0, limit);
-        assertArrayEquals("after append xCoordinates", dst.getXCoordinates(), limit,
-                src.getXCoordinates(), 0, limit);
-        assertArrayEquals("after append yCoordinates", dst.getYCoordinates(), limit,
-                src.getYCoordinates(), 0, limit);
-        assertArrayEquals("after append pointerIds", dst.getPointerIds(), limit,
-                src.getPointerIds(), 0, limit);
-        assertArrayEquals("after append times", dst.getTimes(), limit,
-                src.getTimes(), 0, limit);
+        dst.append(src, 0, srcLen);
+        assertEquals("after append size", dstLen + srcLen, dst.getPointerSize());
+        assertTrue("after append size primitive length",
+                dst.getPointerIds().length >= dstLen + srcLen);
+        assertArrayEquals("after append xCoordinates", dstCopy.getXCoordinates(), 0,
+                dst.getXCoordinates(), 0, dstLen);
+        assertArrayEquals("after append yCoordinates", dstCopy.getYCoordinates(), 0,
+                dst.getYCoordinates(), 0, dstLen);
+        assertArrayEquals("after append pointerIds", dstCopy.getPointerIds(), 0,
+                dst.getPointerIds(), 0, dstLen);
+        assertArrayEquals("after append times", dstCopy.getTimes(), 0,
+                dst.getTimes(), 0, dstLen);
+        assertArrayEquals("after append xCoordinates", dst.getXCoordinates(), dstLen,
+                src.getXCoordinates(), 0, srcLen);
+        assertArrayEquals("after append yCoordinates", dst.getYCoordinates(), dstLen,
+                src.getYCoordinates(), 0, srcLen);
+        assertArrayEquals("after append pointerIds", dst.getPointerIds(), dstLen,
+                src.getPointerIds(), 0, srcLen);
+        assertArrayEquals("after append times", dst.getTimes(), dstLen,
+                src.getTimes(), 0, srcLen);
     }
 
     private static void assertArrayEquals(String message, int[] expecteds, int expectedPos,