Why is this an issue?
Using the same value on either side of a binary operator is almost always a mistake. In the case of logical operators, it is either a copy/paste
error and therefore a bug, or it is simply wasted code, and should be simplified. In the case of bitwise operators and most binary mathematical
operators, having the same value on both sides of an operator yields predictable results, and should be simplified.
Noncompliant code example
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.
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
- CERT, MSC12-C. - Detect and remove code that has no effect or is never executed
- {rule:java:S1656} - Implements a check on
=
.