@NonNull
    @Override
    public Object[] toArray() {
        Object[] result = new Object[mSize];
        System.arraycopy(mArray, 0, result, 0, mSize);
        return result;
    }
Return the number of items in this array map.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/util/collection/ArraySet.java