gistfile1.txt

@Java

When you override the equals method, you must adhere to its general contract. Here 
is the contract, copied from the specification for java.lang.Object:

The equals method implements an equivalence relation:

• It is reflexive: For any reference value x, x.equals(x) must return true.
• It is symmetric: For any reference values x and y, x.equals(y) must return true 
if and only if y.equals(x) returns true.
• It is transitive: For any reference values x, y, and z, if x.equals(y) 
returns true and y.equals(z) returns true, then x.equals(z) must return true.
• It is consistent: For any 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 object is modified.
• For any non-null reference value x, x.equals(null) must return false.