java - hashCode(), equals(Object) and compareTo(Class) -

i've following following vertex class , implements equals, hashcode , compareto method. hashmap returns null. don't know why?

public class vertex implements comparable<vertex> {     int id;      public vertex(int number) {         id = number;     }      public boolean equals(object other) {         if (other == null)             return false;         else if (other.getclass() != this.getclass())             return false;         else {             vertex copy = (vertex) other;             if (copy.id == this.id)                 return true;             else                 return false;         }     }      public int hascode() {         int prime = 31;         int smallprime = 3;         int hashcode = this.id ^ smallprime - prime * this.hascode();         return hashcode;     }      public int compareto(vertex other) {         if (this.id < other.id)             return -1;         else if (this.id > other.id)             return 1;         else             return 0;     }  } 

your method called hascode(). make hashcode() instead.

i'd suggest using ide automatically generate hashcode() , equals(..). generate proper methods (right have recursive call in hashcode())