== Why is this an issue?

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=== Noncompliant code example

[source,java]
----
if ( a == a ) { // always true
  doZ();
}
if ( a != a ) { // always false
  doY();
}
if ( a == b && a == b ) { // if the first one is true, the second one is too
  doX();
}
if ( a == b || a == b ) { // if the first one is true, the second one is too
  doW();
}

int j = 5 / 5; //always 1
int k = 5 - 5; //always 0

c.equals(c); //always true
----

=== Exceptions

* This rule ignores ``++*++``, ``+``, and ``++=++``. 
* The specific case of testing a floating point value against itself is a valid test for ``++NaN++`` and is therefore ignored.
* Similarly, left-shifting 1 onto 1 is common in the construction of bit masks, and is ignored.


[source,java]
----
float f;
if(f != f) { //test for NaN value
  System.out.println("f is NaN");
}

int i = 1 << 1; // Compliant
int j = a << a; // Noncompliant
----

== Resources

* https://wiki.sei.cmu.edu/confluence/x/5dUxBQ[CERT, MSC12-C.] - Detect and remove code that has no effect or is never executed
* S1656 - Implements a check on ``++=++``. 

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== Implementation Specification
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== Comments And Links
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=== on 21 Nov 2024, 16:48:00 Alban Auzeill wrote:
[test-code-support-investigation-for-java] Decision for scope: Keep 'Main'. Tests do this to validate `equals`.

=== on 1 Oct 2014, 11:39:51 Nicolas Peru wrote:
Sub task for RSPEC-1764 with updated description for Java, please review.

=== on 1 Oct 2014, 11:44:49 Ann Campbell wrote:
\[~nicolas.peru] I question retaining this noncompliant example:

----
if (5 / 5) { // always 1
  doV();
}
----

In C, >=1 evaluates to true & 0 evaluates to false. Is it that the same holds true in Java but it's just considered very bad form? If so, then why eliminate this one:

----
if (5 - 5) { // always 0
  do_u();
}
----
?


Also, we have a different rule that yells at people for using equality operators with floating-point numbers, so the first exception is doubly confusing

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