Enable checkstyle for simple boolean expressions

airsonic-main/src/main/java/org/airsonic/player/controller/DownloadController.java

@@ -240,7 +240,7 @@ public class DownloadController implements LastModified {
                 }
             }
         }
-        if (coverArtFile != null && coverArtFile.exists() && cover_embedded == false) {
+        if (coverArtFile != null && coverArtFile.exists() && !cover_embedded) {
             zip(out, coverArtFile.getParentFile(), coverArtFile, status, range);
         }
 

airsonic-main/src/main/java/org/airsonic/player/monitor/MetricsManager.java

@@ -79,7 +79,7 @@ public class MetricsManager {
      */
     public TimerBuilder condition(boolean ifTrue) {
         if (metricsActivatedByConfiguration()) {
-            if (ifTrue == false) {
+            if (!ifTrue) {
                 return conditionFalseTimerBuilderSingleton;
             }
             return new TimerBuilder();

checkstyle.xml

@@ -38,6 +38,8 @@
         <module name="OneStatementPerLine"/>
         <module name="ParenPadCheck"/>
         <module name="RedundantImport"/>
+        <module name="SimplifyBooleanExpression"/>
+        <module name="SimplifyBooleanReturn"/>
         <module name="StringLiteralEquality"/>
         <module name="TypecastParenPad"/>
         <module name="UnusedImports"/>