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  1. import java.util.Map;
  2. import java.util.stream.Collectors;
  3. import java.util.stream.Stream;
  4.  
  5. class Ideone {
  6.  
  7. 	static class Stats {
  8. 	    final int data, num;
  9.  
  10. 	    public Stats() {
  11. 	    	data = num = 0;
  12. 	    }
  13.  
  14. 	    public Stats(int data, int num) {
  15. 	    	this.data = data;
  16. 	    	this.num = num;
  17. 		}
  18.  
  19. 	    public Stats merge(Stats stats) {
  20. 	    	return new Stats(this.data+stats.data, this.num+stats.num);
  21. 	    }
  22.  
  23. 	    public int getData(){
  24. 	        return data;
  25. 	    }
  26. 	    public int getNum(){
  27. 	        return num;
  28. 	    }
  29.  
  30. 	    @Override
  31. 		public String toString() {
  32. 			return "{" + data + "," + num + "}";
  33. 	    }
  34. 	}
  35.  
  36. 	public static void main(String[] args) {
  37. 		Stream<String> lines = Stream.of("item1,16,2",
  38. 			      "item2,17,3",
  39. 			      "item1,16,5"); // sample input
  40.  
  41. 		Map<String, Stats> map = lines.map(s -> s.split(",")).collect(
  42. 				Collectors.groupingBy(a -> a[0], 
  43. 						Collectors.mapping(a -> new Stats(Integer.parseInt(a[1]), Integer.parseInt(a[2])), 
  44. 								Collectors.reducing(new Stats(), Stats::merge))));
  45.  
  46. 		System.out.println(map);
  47. 	}
  48.  
  49. }
  50.  
Success #stdin #stdout 0.2s 320512KB
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Standard input is empty
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{item2={17,3}, item1={32,7}}
https://ideone.com/Ar0Ccg
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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