But i don't get the part why do we need to override those two method what is the wrong happening here?
Well, you don't have to override those two methods.
The default equals() method (from Object class) will return the value of true, if two references are referring to the same instance. The default hashCode() method will use the identity hash as the hashcode. This hashcode will very likely be different for different instances, but may not be as there can only be so many different values for hashcode.
If this behavior is fine for your purposes, then there is no need to override those two methods.
Henry