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  1. import java.io.*;
  2. import java.util.*;
  3.  
  4. class Experiment {
  5.     public static void main(String args[]) {
  6.         Student s1 = new Student("uvw");
  7.         Student s2 = new Student("xyz");
  8.         HashSet<Student> set = new HashSet<>();
  9.         set.add(s1);
  10.         set.add(s2);
  11.         System.out.println(set);
  12.  
  13.         Student s3 = new Student("uvw");
  14.  
  15.         System.out.println("s3 equals s1 ? " + s1.equals(s3));
  16.         System.out.println("s1 hash = " + s1.hashCode());
  17.         System.out.println("s3 hash = " + s3.hashCode());
  18.  
  19.         System.out.println( set.contains(s3) );
  20.     }
  21. }
  22. class Student{
  23.  
  24.     String name;
  25.  
  26.     public Student(String name) {this.name=name;}
  27.  
  28.    /* @Override
  29.     public int hashCode() {
  30.         return name.length();
  31.     }*/
  32.  
  33.     @Override
  34.     public boolean equals(Object obj) {
  35.         if (name.equals( ((Student)obj).name ))
  36. 	return true;
  37.         return false;
  38.     }
  39.  
  40.     @Override
  41.     public String toString() {
  42.         return "Student{" +
  43.                 "name='" + name + '\'' +
  44.                 '}';
  45.     }
  46. }
Success #stdin #stdout 0.04s 4386816KB
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Standard input is empty
stdout
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[Student{name='uvw'}, Student{name='xyz'}]
s3 equals s1 ? true
s1 hash = 1735600054
s3 hash = 2133927002
false
https://ideone.com/cJuFvy
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
secret

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