public class MyClass { private int id; private String name; // constructor and getters/setters here @Override public int hashCode() { int result = 17; // arbitrary prime number result = 31 * result + id; // multiply by another prime number and add instance variables result = 31 * result + name.hashCode(); // repeat for each relevant variable return result; } }In this example, we define a custom hash code implementation for a class called MyClass. The hash code is calculated based on the values of two instance variables, id and name. The multiplication factor of 31 and initial value of 17 are commonly used in hash code implementations to reduce collisions. Another package library where T hashCode might be used is java.lang. This is because all Java objects inherit a default implementation of hashCode() from the Object class, which is part of the java.lang package. However, it is common practice to override this default implementation with a custom one for classes that will be used in hash-based data structures.