The hashCode Method [java]

• A hash code is an integer that is derived from an object.
  Hash Codes Resulting from the hashcode Method

The hashCode method should return an integer (which can be negative).Just combine the hash codes of the instance fields so that the hash codes for different objects are likely to be widely scattered.
For exmaple ,here is an hashCode method for the Employee class:

 class Employee
 {
     public int hashCode()
     {
         return 7 * name.hashCode() + 11  * new Double(salary).hashCode() + 13 * hireDay.hashCode();
         }
         ....
  }

• java.lang.Object
  • int hashCode()
    returns a hash code for this object. A hash code can be any integer, positive or negative. Equal objects need to return identical hash codes.
• java.lang.Objects
  • int hash(Object… objects)
    returns a hash code that is combined from the hash codes of all supplied objects.
  • static int hashCode(Object a)
    returns 0 if a is null or a.hashCode() otherwise.
• java.util.Arrays
  • static int hashCode(type[] a)
    computes the hash code of the array a, which can have component type Object, int, long, short, char, byte, boolean, float, or double.