Remove ProjectFileIndex.SERVICE usage due to deprecation in newer IDEA versions

Author: jshiell

src/main/java/org/infernus/idea/checkstyle/actions/ScanCurrentFile.java

@@ -92,20 +92,18 @@ private VirtualFile getSelectedFile(
 
         // validate selected file against scan scope
         if (selectedFile != null && scanScope != ScanScope.Everything) {
-            final ProjectFileIndex projectFileIndex = ProjectFileIndex.SERVICE.getInstance(project);
-            if (projectFileIndex != null) {
-                if (!projectFileIndex.isInSourceContent(selectedFile)) {
+            final ProjectFileIndex projectFileIndex = ProjectFileIndex.getInstance(project);
+            if (!projectFileIndex.isInSourceContent(selectedFile)) {
+                selectedFile = null;
+            }
+            if (!scanScope.includeNonJavaSources() && selectedFile != null) {
+                if (!FileTypes.isJava(selectedFile.getFileType())) {
                     selectedFile = null;
                 }
-                if (!scanScope.includeNonJavaSources() && selectedFile != null) {
-                    if (!FileTypes.isJava(selectedFile.getFileType())) {
-                        selectedFile = null;
-                    }
-                }
-                if (!scanScope.includeTestClasses() && selectedFile != null) {
-                    if (projectFileIndex.isInTestSourceContent(selectedFile)) {
-                        selectedFile = null;
-                    }
+            }
+            if (!scanScope.includeTestClasses() && selectedFile != null) {
+                if (projectFileIndex.isInTestSourceContent(selectedFile)) {
+                    selectedFile = null;
                 }
             }
         }

src/main/java/org/infernus/idea/checkstyle/checker/PsiFileValidator.java

@@ -29,7 +29,7 @@ private PsiFileValidator() {
     public static boolean isScannable(@Nullable final PsiFile psiFile,
                                       @NotNull final Optional<Module> module,
                                       @NotNull final PluginConfigurationManager pluginConfig,
-                                      @Nullable ConfigurationLocation overrideConfigLocation) {
+                                      @Nullable final ConfigurationLocation overrideConfigLocation) {
         return psiFile != null
                 && psiFile.isValid()
                 && psiFile.isPhysical()
@@ -64,10 +64,10 @@ private static boolean isGenerated(final PsiFile psiFile) {
     private static boolean isInSource(
             @NotNull final PsiFile psiFile,
             @NotNull final PluginConfigurationManager pluginConfig,
-            @Nullable ConfigurationLocation overrideConfigLocation) {
+            @Nullable final ConfigurationLocation overrideConfigLocation) {
         final boolean shouldBeScanned = pluginConfig.getCurrent().getScanScope() == ScanScope.Everything
                 || (psiFile.getVirtualFile() != null
-                        && ProjectFileIndex.SERVICE.getInstance(psiFile.getProject()).isInSourceContent(psiFile.getVirtualFile()));
+                        && ProjectFileIndex.getInstance(psiFile.getProject()).isInSourceContent(psiFile.getVirtualFile()));
         return shouldBeScanned && isInNamedScopeIfPresent(
                 psiFile,
                 overrideConfigLocation != null
@@ -79,7 +79,8 @@ private static boolean isInSource(
      * Returns true, if the given psiFile is contained in any named scope of the given pluginConfig.
      * If no NamedScope is provided, true will be returned.
      */
-    private static boolean isInNamedScopeIfPresent(@NotNull PsiFile psiFile, Collection<ConfigurationLocation> activeLocations) {
+    private static boolean isInNamedScopeIfPresent(@NotNull final PsiFile psiFile,
+                                                   final Collection<ConfigurationLocation> activeLocations) {
         return activeLocations.stream()
                 .map(ConfigurationLocation::getNamedScope)
                 .flatMap(Optional::stream)