HashCode (Guava: Google Core Libraries for Java 16.0 API)

Indicates whether some other object is “equal to” this one.

The equals method implements an equivalence relation
on non-null object references:

• It is reflexive: for any non-null reference value
  x, x.equals(x) should return
  true.
• It is symmetric: for any non-null reference values
  x and y, x.equals(y)
  should return true if and only if
  y.equals(x) returns true.
• It is transitive: for any non-null reference values
  x, y, and z, if
  x.equals(y) returns true and
  y.equals(z) returns true, then
  x.equals(z) should return true.
• It is consistent: for any non-null reference values
  x and y, multiple invocations of
  x.equals(y) consistently return true
  or consistently return false, provided no
  information used in equals comparisons on the
  objects is modified.
• For any non-null reference value x,
  x.equals(null) should return false.

The equals method for class Object implements
the most discriminating possible equivalence relation on objects;
that is, for any non-null reference values x and
y, this method returns true if and only
if x and y refer to the same object
(x == y has the value true).

Note that it is generally necessary to override the hashCode
method whenever this method is overridden, so as to maintain the
general contract for the hashCode method, which states
that equal objects must have equal hash codes.