Comment by Pinei on "Can anyone explain to me the use of HashTables over HashMaps, the use of HashMap over ArrayList and the use of ArrayList over LinkedList ?" | Hashnode
Both are a key/value store, but there are few differences between Hashtable an HashMap.
Hashtable does not allow null keys or null values. HashMap allows one null key and any number of null values.
Hashtable is thread safe (synchronized), whereas HashMap is not. This makes HashMap better for non-threaded use. Unsynchronized Objects perform better than synchronized ones.