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Importance of HashSet in Java
The HashSet use Hashing to manipulate data. Let us see an example −
Example
import java.util.*;
public class Demo{
private final String f_str, l_str;
public Demo(String f_str, String l_str){
this.f_str = f_str;
this.l_str = l_str;
}
public boolean equals(Object o){
if (o instanceof Demo)
return true;
Demo n = (Demo)o;
return n.f_str.equals(f_str) && n.l_str.equals(l_str);
}
public static void main(String[] args){
Set<Demo> my_set = new HashSet<Demo>();
my_set.add(new Demo("Joe", "Goldberg"));
System.out.println("Added a new element to the set");
System.out.println("Does the set contain a new instance of the object? ");
System.out.println(my_set.contains(new Demo("Jo", "Gold")));
}
}
Output
Added a new element to the set Does the set contain a new instance of the object? false
The ‘Demo’ class contains a final string and a constructor. An equals function is defined that checks if an object is an instance of a specific class. It returns true if it is an instance otherwise casts the object to the class and checks using the ’equals’ function. In the main function, a new Set is created and an instance is created. This is checked for using the ‘instanceof’ operator.
Updated on: 23-Nov-2023
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