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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.*;
  4. import java.lang.*;
  5. import java.io.*;
  6. import java.util.HashMap;
  7. import java.util.Map;
  8. import java.util.Map.Entry;
  9.  
  10. /* Name of the class has to be "Main" only if the class is public. */
  11. class Ideone
  12. {
  13. 		public static void main(String[] args) {
  14. 		Map<String, Integer> dates = new HashMap<String, Integer>();
  15. 		dates.put("2015-07-14", 40);
  16. 		dates.put("2015-07-15", 8);
  17. 		dates.put("2015-07-16", 0);
  18. 		dates.put("2015-07-17", 0);
  19. 		dates.put("2015-07-18", 0);
  20. 		dates.put("2015-08-01", 1);
  21. 		dates.put("2015-08-02", 1);
  22. 		dates.put("2015-08-03", 2);
  23. 		dates.put("2015-08-04", 1);
  24.  
  25. 		Map<String, Integer> result = new HashMap<String, Integer>();
  26.  
  27. 		for (Entry<String, Integer> entry  : dates.entrySet()) {
  28. 			String key = entry.getKey().split("-")[0] + "/" + entry.getKey().split("-")[1];
  29. 			Integer value = entry.getValue();
  30. 			Integer oldValue = result.get(key) != null ? result.get(key) : 0;
  31. 			result.put(key, oldValue + value);
  32. 		}
  33.  
  34. 		for (Entry<String, Integer> entry  : result.entrySet()) {
  35. 			System.out.println("Month " + entry.getKey() + "- Value = " + entry.getValue());
  36. 		}
  37.  
  38. 	}
  39.  
  40. }
Success #stdin #stdout 0.1s 320512KB
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Month 2015/08- Value = 5
Month 2015/07- Value = 48
https://ideone.com/Rzn19V
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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