Add Checkstyle SimplifyBooleanExpression
diff --git a/src/conf/checkstyle.xml b/src/conf/checkstyle.xml
index 78904b5..0ab7553 100644
--- a/src/conf/checkstyle.xml
+++ b/src/conf/checkstyle.xml
@@ -69,6 +69,7 @@
       <property name="illegalPattern" value="true" />
       <property name="message" value="Trailing whitespace" />
     </module>
+    <module name="SimplifyBooleanExpression" />
     <module name="TypecastParenPad" />
     <module name="UnusedImports" />
     <module name="WhitespaceAfter" />