Data Structures and Algorithms
with Object-Oriented Design Patterns in Java 
Out of all the Java primitive types, the so-called integral types are the simplest to hash into integers. The integral data types are byte, short, int, long, and char. Since the underlying representation of such data types can be viewed as an integer, the hash function is trivial. A suitable function f for an integral data type is the identity function:
Program 
completes the definition of the Int wrapper class
introduced in Program .
In this case, the hashCode method simply returns
the contents of the value field.
Clearly, the running time of of the hashCode method is O(1).
Program: Int class hashCode method.
Copyright © 1998 by Bruno R. Preiss, P.Eng. All rights reserved.