Since Checkstyle 3.4
Restricts the number of boolean operators (&&
, ||
,
&
, |
and ^
) in an expression.
Rationale: Too many conditions leads to code that is difficult to read and hence debug and maintain.
Note that the operators &
and
|
are not only integer bitwise operators, they are also the
non-shortcut versions of the boolean operators
&&
and ||
.
Note that &
, |
and ^
are not checked
if they are part of constructor or method call
because they can be applied to non-boolean variables and
Checkstyle does not know types of methods from different classes.
To configure the check:
<module name="Checker"> <module name="TreeWalker"> <module name="BooleanExpressionComplexity"/> </module> </module>
Code Example:
public class Test { public static void main(String ... args) { boolean a = true; boolean b = false; boolean c = (a & b) | (b ^ a); // OK, 1(&) + 1(|) + 1(^) = 3 (max allowed 3) boolean d = (a & b) ^ (a || b) | a; // violation, 1(&) + 1(^) + 1(||) + 1(|) = 4 } }
To configure the check with 5 allowed operation in boolean expression:
<module name="Checker"> <module name="TreeWalker"> <module name="BooleanExpressionComplexity"> <property name="max" value="5"/> </module> </module> </module>
Code Example:
public class Test { public static void main(String ... args) { boolean a = true; boolean b = false; boolean c = (a & b) | (b ^ a) | (a ^ b); // OK, 1(&) + 1(|) + 1(^) + 1(|) + 1(^) = 5 boolean d = (a | b) ^ (a | b) ^ (a || b) & b; // violation, // 1(|) + 1(^) + 1(|) + 1(^) + 1(||) + 1(&) = 6 } }
To configure the check to ignore &
and
|
:
<module name="Checker"> <module name="TreeWalker"> <module name="BooleanExpressionComplexity"> <property name="tokens" value="BXOR,LAND,LOR"/> </module> </module> </module>
Code Example:
public class Test { public static void main(String ... args) { boolean a = true; boolean b = false; boolean c = (!a && b) | (a || !b) ^ a; // OK, 1(&&) + 1(||) + 1(^) = 3 // | is ignored here boolean d = a ^ (a || b) ^ (b || a) & a; // violation, 1(^) + 1(||) + 1(^) + 1(||) = 4 // & is ignored here } }
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