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  1. import java.util.Arrays;
  2. import java.util.ArrayList;
  3. import java.util.Collections;
  4. import java.util.HashSet;
  5. import java.util.List;
  6. import java.util.Objects;
  7. import java.util.Set;
  8.  
  9. class Ideone {
  10. 	public static void main (String[] args) {
  11. 		ArrayList<Mobile> mobiles = new ArrayList<>();
  12. 		mobiles.add(
  13. 			Mobile.of(
  14. 				Plan.of("P1", "Plan 1"),
  15. 				Plan.of("P2", "Plan 2")));
  16. 		mobiles.add(Mobile.of(
  17. 				Plan.of("P1", "Plan 1"),
  18. 				Plan.of("P2", "Plan 2"),
  19. 				Plan.of("P3", "Plan 3"),
  20. 				Plan.of("P4", "Plan 4")));
  21. 		mobiles.add(Mobile.of(
  22. 				Plan.of("P1", "Plan 1"),
  23. 				Plan.of("P2", "Plan 2"),
  24. 				Plan.of("P5", "Plan 5"),
  25. 				Plan.of("P6", "Plan 6")));
  26. 		Set<Plan> commonPlans = extractCommonPlans(mobiles);
  27. 		System.out.println(commonPlans);
  28. 	}
  29.  
  30. 	public static Set<Plan> extractCommonPlans(List<Mobile> mobiles) {
  31. 		if (Objects.isNull(mobiles) || mobiles.isEmpty()) {
  32. 			return Collections.emptySet();
  33. 		}
  34.  
  35. 		HashSet<Plan> initialSet = new HashSet<>(mobiles.get(0).getPlans());
  36. 		return mobiles.stream()
  37. 			.map(Mobile::getPlans)
  38. 			.map(HashSet<Plan>::new)
  39. 			.reduce(initialSet, (plan1, plan2) -> { 
  40. 				plan1.retainAll(plan2);
  41. 				return plan1;
  42. 			});
  43. 	}
  44. }
  45.  
  46. class Mobile {
  47.     private final List<Plan> plans;
  48.  
  49.     private Mobile(List<Plan> plans) {
  50.     	this.plans = plans;
  51.     }
  52.  
  53.     public static Mobile of(Plan... plans) {
  54.     	return new Mobile(Arrays.asList(plans));
  55.     }
  56.  
  57.     public List<Plan> getPlans() {
  58.     	return plans;
  59.     }
  60. }
  61.  
  62. class Plan {
  63.     private final String id;
  64.     private final String name;
  65.  
  66.     private Plan(String id, String name) {
  67.     	this.id = id;
  68.     	this.name = name;
  69.     }
  70.  
  71.     public static Plan of(String id, String name) {
  72.     	return new Plan(id, name);
  73.     }
  74.  
  75.     @Override 
  76.     public boolean equals(Object thatObject) {
  77.     	if (this == thatObject) {
  78.     		return true;
  79.     	}
  80.     	if (getClass() != thatObject.getClass()) {
  81.     		return false;
  82.     	}
  83.     	Plan that = (Plan) thatObject;
  84.     	return Objects.equals(id, that.id) 
  85.     			&& Objects.equals(name, that.name);
  86.     }
  87.  
  88.     @Override 
  89.     public int hashCode() {
  90.     	return Objects.hash(id, name);
  91.     }
  92.  
  93.     @Override
  94.     public String toString() {
  95.     	return String.format("Plan{id=\"%s\", name=\"%s\"}", id, name);
  96.     }
  97. }
Success #stdin #stdout 0.08s 34664KB
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Standard input is empty
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[Plan{id="P1", name="Plan 1"}, Plan{id="P2", name="Plan 2"}]
https://ideone.com/cUKZuY
language:
Java (HotSpot 12)
created:
5 years ago
visibility:
public

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