hashset

[gunjan khanuja]

import java.util.HashSet;

public class Propagate {
    
    private String str;
    
    public Propagate(String str) {
        this.str = str;
    }
        
    @Override
    public int hashCode() {             
        return this.str.hashCode();
    }
    
    @Override
    public boolean equals(Object obj) { 
        return this.str.equals(obj);
    }
    
    public static void main(String args[]) {
       Propagate h1 = new Propagate("1");
       Propagate h2 = new Propagate("1");
        String s1 = new String("2");
        String s2 = new String("2");
       
        HashSet<Object> hs = new HashSet<Object>();
        hs.add(h1);
        hs.add(h2);
        hs.add(s1);
        hs.add(s2);
       
        
        System.out.print(hs.size());
    }
}

i run this code snippet and this gives me output 3
I understand that hashset contains unique elements so the string s1 and s2 is not added twice but why is Propagate object being added twice..???explain

[Anayonkar Shivalkar]

Hi gunjan khanuja,

Welcome to CodeRanch!

gunjan khanuja wrote:why is Propagate object being added twice..???explain

Well, I would have liked a 'please' here

Anyways, here's a hint : take a close look at your equals method. What exactly are you trying to equate?

[gunjan khanuja]

Well,I am trying to compare the string value with object 's value.But i dont understand the output.
please explain in detail what all is happening in the snippet???

[Matthew Brown]

Anayonkar's pointed you in the right direction. In your equals() method, you are comparing a String with a Propagate.

[Seetharaman Venkatasamy]

still not clear? then you customize your equals method as in

  @Override  
    public boolean equals(Object obj) {    	
    	System.out.println("got it????"+ (obj instanceof Propagate));
    	Propagate p = (Propagate)obj;
    	String str = p.str;
        return this.str.equals(str);  
    }

[Helen Ma]

Another hint : try to System.out.println(h1.str.equals(h2)). Is the answer true or false? I think it is false.