Fix Gradle PMD and Checkstyle (#1318)

* Fixes #1306

Nested Cases with Complex Expressions

* Reduce coverage for Java 8

* GROUP BY with Complex Expressions

Fixes #1308

* Update Sets with Complex Expressions

Fixes #1316

* Update Sets with Complex Expressions

Fix existing tests
Add tests for the new functionality

* Implement PMD/Codacy recommendations

* Add Checkstyle Configuration to Gradle
Add Checkstyle Config files
Fix additional exceptions in Test Sources

Author: manticore-projects

build.gradle

@@ -5,6 +5,7 @@ plugins {
     id 'jacoco'
     id "com.github.spotbugs" version "4.7.2"
     id 'pmd'
+    id 'checkstyle'
 
     // download the RR tools which have no Maven Repository
     id "de.undercouch.download" version "4.1.2"
@@ -44,6 +45,10 @@ compileJavacc {
 java {
     withSourcesJar()
     withJavadocJar()
+
+    spotbugs
+    pmd
+
 }
 
 jacoco {
@@ -98,9 +103,10 @@ pmd {
 
     sourceSets = [sourceSets.main]
 
-    // clear the ruleset in order to use configured rules only, although we should apply the Prio 1 rules eventually
+    // clear the ruleset in order to use configured rules only
     ruleSets = []
-    rulesMinimumPriority = 1
+    
+    //rulesMinimumPriority = 1
 
     ruleSetFiles = files("ruleset.xml")
 
@@ -111,6 +117,19 @@ pmd {
     }
 }
 
+checkstyle {
+    toolVersion "8.45.1"
+    sourceSets = [sourceSets.main, sourceSets.test]
+    configFile =rootProject.file('config/checkstyle/checkstyle.xml')
+}
+
+tasks.withType(Checkstyle) {
+    reports {
+        xml.required = false
+        html.required = true
+    }
+}
+
 task renderRR() {
     doLast {
         // these WAR files have been provided as a courtesy by Gunther Rademacher 

config/checkstyle/checkstyle.xml

@@ -0,0 +1,36 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+          "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
+          "https://checkstyle.org/dtds/configuration_1_3.dtd">
+
+<module name="Checker">
+  <module name="SuppressWarningsFilter" />
+  <module name="FileTabCharacter" />
+  <!-- git checkout may change linefeeds on the fly
+  <module name="RegexpMultiline">
+      <property name="format" value="(?s:(\r\n|\r).*)" />
+      <property name="message" value="CRLF and CR line endings are prohibited, but this file uses them." />
+  </module>
+  -->
+  <module name="TreeWalker">
+    <module name="AvoidNestedBlocks" />
+    <module name="ConstantName" />
+    <module name="EmptyCatchBlock" />
+    <module name="EmptyStatement" />
+    <module name="MissingOverride" />
+    <module name="MultipleVariableDeclarations" />
+    <module name="ParameterAssignment" />
+    <module name="StringLiteralEquality" />
+    <module name="RedundantImport" />
+    <module name="UnusedImports" />
+
+    <module name="WhitespaceAfter" />
+
+    <module name="NeedBraces" />
+    <module name="UnnecessaryParentheses" />
+    <module name="LeftCurly" />
+    <module name="RightCurly" />
+
+    <module name="SuppressWarningsHolder" />
+  </module>
+</module>