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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.function.*;
  7. import java.util.stream.*;
  8. import static java.util.stream.Collectors.*;
  9. import java.util.List;
  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) throws java.lang.Exception
  14. 	{
  15. 	  List<T> source = new ArrayList<>();
  16.       source.add(new T(12345, 9000, 999));
  17.         source.add(new T(12345, 8000, 999));
  18.         source.add(new T(1234, 4500, 888));
  19.         source.add(new T(1234, 8500, 888));
  20.         source.add(new T(1234, 7500, 888));
  21.         source.add(new T(1234, 7500, 999));
  22.         source.add(new T(1234, 7500, 999));
  23.         source.add(new T(1234, 8500, 999));
  24.         int offerId = 999;
  25.         List<T> result = source.stream()
  26.             .filter(x -> x.getOfferId() == offerId)
  27.             .collect(toMap(T::getCustomerId,
  28.                     Function.identity(),
  29.                     BinaryOperator.maxBy(Comparator.comparingInt(T::getStake))))
  30.             .values()
  31.             .stream()
  32.             .collect(groupingBy(T::getStake))
  33.             .values()
  34.             .stream()
  35.             .flatMap(x -> x.stream().limit(20))
  36.             .collect(Collectors.toList());
  37.  
  38.  
  39.         System.out.println(result);
  40.  
  41. 	}
  42. }
  43.  
  44. class T {
  45.     public T(int customerId, int stake, int offerId) {
  46.         this.customerId = customerId;
  47.         this.stake = stake;
  48.         this.offerId = offerId;
  49.     }
  50.  
  51.     @Override
  52.     public String toString() {
  53.         return "T{" +
  54.                 "customerId=" + customerId +
  55.                 ", stake=" + stake +
  56.                 ", offerId=" + offerId +
  57.                 '}';
  58.     }
  59.  
  60.     int customerId;
  61.  
  62.     public int getCustomerId() {
  63.         return customerId;
  64.     }
  65.  
  66.     public void setCustomerId(int customerId) {
  67.         this.customerId = customerId;
  68.     }
  69.  
  70.     public int getStake() {
  71.         return stake;
  72.     }
  73.  
  74.     public void setStake(int stake) {
  75.         this.stake = stake;
  76.     }
  77.  
  78.     public int getOfferId() {
  79.         return offerId;
  80.     }
  81.  
  82.     public void setOfferId(int offerId) {
  83.         this.offerId = offerId;
  84.     }
  85.  
  86.     int stake;
  87.     int offerId;
  88. }
Success #stdin #stdout 0.15s 2184192KB
comments ()
stdin 
Standard input is empty
stdout 
[T{customerId=1234, stake=8500, offerId=999}, T{customerId=12345, stake=9000, offerId=999}]
https://ideone.com/gbn2Nk
language:
Java (HotSpot 12)
created:
6 years ago
visibility:
public

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