Recommended data-structures:
- ArrayMap<K,V> in place of HashMap<K,V>
- ArraySet<K,V> in place of HashSet<K,V>
- SparseArray<V> in place of HashMap<Integer,V>
- SparseBooleanArray in place of HashMap<Integer,Boolean>
- SparseIntArray in place of HashMap<Integer,Integer>
- SparseLongArray in place of HashMap<Integer,Long>
- LongSparseArray<V> in place of HashMap<Long,V>
SparseArray
原文：http://www.cnblogs.com/wutianlong/p/6800612.html
