java - How to convert long value to Set of string -

i have map values:

private static map<string, long> hodnotyudaju = new hashmap<string, long>();  static {     hodnotyudaju.put("a", 1l);     hodnotyudaju.put("b", 2l);     hodnotyudaju.put("b", 4l);     hodnotyudaju.put("d", 8l);     hodnotyudaju.put("e", 16l);     hodnotyudaju.put("f", 32l);     hodnotyudaju.put("g", 64l);     hodnotyudaju.put("h", 128l);     hodnotyudaju.put("i", 256l);     hodnotyudaju.put("j", 512l);     .     .     . } 

and method convert set of value long

public static long bitovahodnotaseznamuudaju(set<string> udaje) {     long bitovahodnota = 0;      (string udaj : udaje) {         long tmp = hodnotyudaju.get(udaj);         if (tmp != null)             bitovahodnota += tmp;     }      return bitovahodnota; } 

how can implement method vice versa ? need long create set set of string

update

methos should looks like:

public static set<string> bin2udaje(long binudaje) {     set<string> udaje = new hashset<string>();     (map.entry<string, long> entry : hodnotyudaju.entryset()) {         if (udaje operation entry.getvalue() ) {             udaje.add(entry.getkey());         }         return udaje;      } } 

it sounds should using enum instead of map. example, while you're guaranteed use values 1, 2, 4, 8... you'll end unambiguous answer - doing on general map won't work.

i suggest use enum has value string if need it, , can use 1l << value.ordinal() long value if want. represent general set of these values, however, can use enumset.

if isn't appropriate, please give more information.

edit: if really want stick existing structure, use:

public static set<string> valuetokeyset(long value) {     set<string> keys = new hashset<string>();     (map.entry<string, long> entry : hodnotyudaju.entryset()) {         if ((value & entry.getvalue()) != 0) {             keys.add(entry.getkey());         }     }     return keys; } 

this will give unexpected results if map doesn't contain single-bit-set values.