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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.  
  7. /* Name of the class has to be "Main" only if the class is public. */
  8. class Ideone
  9. {
  10. 	/**
  11.      * Class representing key in HashMap should be immutable.
  12.      */
  13.     private final static class MyObject {
  14.         private final String fieldString;
  15.         private final int fieldInt;
  16.  
  17.         public MyObject(final String fieldString, final int fieldInt) {
  18.             this.fieldString = fieldString;
  19.             this.fieldInt = fieldInt;
  20.         }
  21.  
  22.         @Override
  23.         public boolean equals(final Object o) {
  24.             if (this == o)
  25.                 return true;
  26.             if (o == null || getClass() != o.getClass())
  27.                 return false;
  28.  
  29.             final MyObject myObject = (MyObject) o;
  30.  
  31.             return Objects.equals(fieldInt, myObject.fieldInt) &&
  32.                 Objects.equals(fieldString, myObject.fieldString);
  33.         }
  34.  
  35.         @Override
  36.         public int hashCode() {
  37.             return Objects.hash(fieldString, fieldInt);
  38.         }
  39.     }
  40.  
  41.     public static void main(String[] args) throws Exception {
  42.         HashMap<MyObject, Object> map = new HashMap<>();
  43.  
  44.         map.put(new MyObject("a", 1), new Object());
  45.         map.put(new MyObject("b", 1), new Object());
  46.         map.put(new MyObject("a", 2), new Object());
  47.         map.put(new MyObject("b", 2), new Object());
  48.         map.put(new MyObject("a", 1), new Object());
  49.  
  50.         if (map.size() == 4) {
  51.             System.out.println("Correct number of elements in map");
  52.         } else {
  53.             System.out.println("Incorrect number of elements in map");
  54.         }
  55.     }
  56. }
Success #stdin #stdout 0.04s 4386816KB
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Standard input is empty
stdout
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Correct number of elements in map
https://ideone.com/EZhEYd
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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