import java.util.Set;

import java.util.HashSet;

public class CustomClassAndHashSet{

public static void main(String[] args){

Set<Planet> sp = new HashSet<Planet>();

sp.add(new Planet("Mercury"));

sp.add(new Planet("Venus"));

sp.add(new Planet("Earth"));

sp.add(new Planet("Mars"));

sp.add(new Planet("Jupiter"));

sp.add(new Planet("Saturn"));

sp.add(new Planet("Uranus"));

sp.add(new Planet("Neptune"));

sp.add(new Planet("Fomalhaut b"));

Planet p1 = new Planet("51 pegasi b");

sp.add(p1);

Planet p2 = new Planet("51 pegasi b");

sp.add(p2);

System.out.println("EQUALS: " + p1.equals(p2));

System.out.println("HASHCODE: " + (p1.hashCode() == p2.hashCode()));

// Duplicate check both equals and hashCode.

System.out.println(sp);

}

}

class Planet{

private String name;

Planet(String name){

this.name = name;

}

@Override

public boolean equals(Object o){

if( !(o instanceof Planet)){

return false;

}

Planet p = (Planet)o;

return this.name.equals(p.name);

}

String getName(){

return name;

}

public String toString(){

return name;

}

public int hashCode(){

return name.hashCode(); // Because String implements the hashCode method validly.

}

}