Maps
Maps in general
Maps - methods
Map interface
      .clear( ) method for Maps
      .containsKey(Obj) method for Maps
      .containsValue(Obj) method for Maps
      .entrySet(Obj) method for Maps
      .get(key) method for Maps
      .isEmpty( ) method for Maps
      .keySet( ) method for Maps
      .put(key, value) method for Maps
      .putAll(Map) method for Maps
      .remove(key) method for Maps
      .size( ) method for Maps
      .values( ) method for Maps
HashMap class
IdentityHashMap class
Map.Entry class
TreeMap class
      .firstKey( ) method
      .lastKey( ) method
      .headMap(key) method
      .tailMap(key) method
      .subMap(fromkey, tokey) method