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  1. import java.util.*;
  2. public class Main {
  3. 	@SuppressWarnings("serial")
  4.     public static void main(String[] args) {
  5.         final Map<String, Object> dates = new HashMap<String, Object>() {
  6.             {
  7.                 put("1999", new HashMap<String, Object>() {
  8.                     {
  9.                         put("3", Arrays.asList("23", "24", "25"));
  10.                         put("4", Arrays.asList("1", "2", "3"));
  11.                     }
  12.                 });
  13.                 put("2001", new HashMap<String, Object>() {
  14.                     {
  15.                         put("11", new HashMap<String, Object>() {
  16.                             {
  17.                                 put("7", Arrays.asList("23", "24", "25"));
  18.                                 put("9", Arrays.asList("1", "2", "3"));
  19.                             }
  20.                         });
  21.                         put("12", "45");
  22.                     }
  23.                 });
  24.             }
  25.         };
  26.         final Map<String, Object> flattened = flatten(dates);
  27.         System.out.println(flattened);
  28.     }
  29.  
  30.     public static Map<String, Object> flatten(final Map<String, Object> map) {
  31.         return flatten("", map, new HashMap<>());
  32.         // use new TreeMap<>() to order map based on key
  33.     }
  34.  
  35.     @SuppressWarnings("unchecked")
  36.     private static Map<String, Object> flatten(final String key, final Map<String, Object> map,
  37.             final Map<String, Object> result) {
  38.         final Set<Map.Entry<String, Object>> entries = map.entrySet();
  39.         if (!entries.isEmpty()) {
  40.             for (final Map.Entry<String, Object> entry : entries) {
  41.                 final String currKey = key + (key.isEmpty() ? "" : '.') + entry.getKey();
  42.                 final Object value = entry.getValue();
  43.                 if (value instanceof Map) {
  44.                     flatten(currKey, (Map<String, Object>) value, result);
  45.                 } else if (value instanceof List) {
  46.                     final List<Object> list = (List<Object>) value;
  47.                     for (int i = 0, size = list.size(); i < size; i++) {
  48.                         result.put(currKey + '.' + (i + 1), list.get(i));
  49.                     }
  50.                 } else {
  51.                     result.put(currKey, value);
  52.                 }
  53.             }
  54.         }
  55.         return result;
  56.     }
  57. }
Success #stdin #stdout 0.12s 36704KB
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{1999.3.2=24, 1999.4.1=1, 1999.3.1=23, 1999.4.3=3, 2001.12=45, 1999.3.3=25, 1999.4.2=2, 2001.11.7.1=23, 2001.11.9.2=2, 2001.11.9.3=3, 2001.11.7.2=24, 2001.11.7.3=25, 2001.11.9.1=1}
https://ideone.com/Yld6ql
language:
Java (HotSpot 12)
created:
3 years ago
visibility:
public

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