Rule Definition
It is a source of great confusion to novice programmers that Java has two ways of thinking about the equality of objects. When used with object references, the == operator returns true only if both references are to the same object. The == operator is used to compare values of primitive types or object references, but it does not test for value or semantic equality. This is the same for the '!=' operator.

Remediation
In the case of a semantic equality replace it with a call to equals method.

Violation Code Sample

int i = 1;
int j = 2;
Integer ia;
Integer ib;

if (i == j) {}     // OK: i and j are primitive types
if (ia == ib) {} // VIOLATION
if (ia != ib) {}  // VIOLATION

Fixed Code Sample

Integer ia;
Integer ib;

if (ia.equals(ib)) {}  // FIXED
if (!ia.equals(ib)) {} // FIXED

Practical Java Programming Language Guide - ISBN 0-201-61646-7, http://javatechniques.com/blog/string-equality-and-interning