The HashSet class defines equality through its equals() method: public boolean equals(Object o) : HashSet « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. HashSet

A HashSet is equal to another object if the other object implements the Set interface, has the same size(), and contains all the same elements.

import java.util.Arrays;
import java.util.HashSet;
import java.util.Set;

public class MainClass {

  public static void main(String[] a) {
    String elements[] = { "A", "B", "C", "D", "E" };
    Set set = new HashSet(Arrays.asList(elements));

    elements = new String[] { "A", "B", "C", "D" };
    Set set2 = new HashSet(Arrays.asList(elements));

    System.out.println(set.equals(set2));
  }
}

false