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  1. import java.util.List;
  2. import java.util.Objects;
  3. import java.util.TreeSet;
  4.  
  5. class Scratch {
  6.     public static void main(String[] args) {
  7.         Foo fooOne = Foo.of(1);
  8.         Foo fooTwo = Foo.of(2);
  9.         Foo fooThree = Foo.of(3);
  10.         TreeSet<Foo> set = new TreeSet<>();
  11.         set.addAll(List.of(fooOne, fooTwo, fooThree));
  12.         System.out.println(set.size());
  13.         fooOne.setValue(4);
  14.         set.add(fooOne);
  15.         System.out.println(set.size());
  16.     }
  17. }
  18.  
  19. class Foo implements Comparable<Foo> {
  20.     private int value;
  21.  
  22.     private Foo(int value) {
  23.         this.setValue(value);
  24.     }
  25.  
  26.     public static Foo of(int value) {
  27.         return new Foo(value);
  28.     }
  29.  
  30.     public int getValue() {
  31.         return value;
  32.     }
  33.  
  34.     public Foo setValue(int value) {
  35.         this.value = value;
  36.         return this;
  37.     }
  38.  
  39.     @Override
  40.     public boolean equals(Object o) {
  41.         if (this == o) {
  42.             return true;
  43.         }
  44.         if (o == null || getClass() != o.getClass()) {
  45.             return false;
  46.         }
  47.         Foo foo = (Foo) o;
  48.         return getValue() == foo.getValue();
  49.     }
  50.  
  51.     @Override
  52.     public int hashCode() {
  53.         return Objects.hash(value);
  54.     }
  55.  
  56.     @Override
  57.     public int compareTo(Foo that) {
  58.         return getValue() - that.getValue();
  59.     }
  60. }
Success #stdin #stdout 0.06s 32800KB
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https://ideone.com/eCFqwF
language:
Java (HotSpot 12)
created:
5 years ago
visibility:
public

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