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  1. import java.util.Set;
  2. import java.util.function.Function;
  3. import java.util.stream.Collectors;
  4.  
  5. class Person {
  6.     private String id;
  7.  
  8.     public Person(String id) {
  9.         this.id = id;
  10.     }
  11.  
  12.     public String getId() {
  13.         return id;
  14.     }
  15. }
  16.  
  17. public class Main {
  18.     public static void main(String[] args) {
  19.         Set<Person> initialSet = Set.of(new Person("123"), new Person("456"));
  20.         Set<Person> currentSet = Set.of(new Person("456"));
  21.  
  22.         Function<Person, String> idMapper = Person::getId;
  23.  
  24.         boolean result = areEntriesRemoved(currentSet, initialSet, idMapper);
  25.         System.out.println(result); // This will print true
  26.     }
  27.  
  28.     private static <T> boolean areEntriesRemoved(Set<T> currentSet, Set<T> initialSet, Function<T, String> idMapper) {
  29.         Set<String> currentIds = currentSet.stream().map(idMapper).collect(Collectors.toSet());
  30.         return initialSet.stream()
  31.                          .map(idMapper)
  32.                          .anyMatch(id -> !currentIds.contains(id));
  33.     }
  34. }
  35.  
Success #stdin #stdout 0.1s 56216KB
comments (?)
stdin 
Standard input is empty
stdout 
true
https://ideone.com/TFJRaT
language:
Java (HotSpot 12)
created:
128 days ago
visibility:
public

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