Class BooleanExpressionComplexityCheck

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.

• Property max - Specify the maximum number of boolean operations allowed in one expression. Type is int. Default value is 3.
• Property tokens - tokens to check Type is java.lang.String[]. Validation type is tokenSet. Default value is: LAND, BAND, LOR, BOR, BXOR.

To configure the check:

 <module name="BooleanExpressionComplexity"/>
 

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="BooleanExpressionComplexity">
   <property name="max" value="5"/>
 </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="BooleanExpressionComplexity">
   <property name="tokens" value="BXOR,LAND,LOR"/>
 </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
    }
  }
 

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

• booleanExpressionComplexity