Minor refactoring for tool tasks

- Don't scan for translations on initialization in TranslationPageGenerator in order to speed up startup time of ToolsRunner
- Extract checking for null / empty array of File#listFiles into a separate method
- Move single method of RuntimeUtils into Utils class

src/test/java/tools/docs/translations/TranslationPageGenerator.java

@@ -34,8 +34,6 @@ public class TranslationPageGenerator implements AutoToolTask {
     private static final int[] COLOR_1 = {12,  9, 0};
     private static final int[] COLOR_2 = { 6, 15, 6};
 
-    private final TranslationsGatherer gatherer = new TranslationsGatherer();
-
     @Override
     public String getTaskName() {
         return "updateTranslations";
@@ -43,6 +41,7 @@ public class TranslationPageGenerator implements AutoToolTask {
 
     @Override
     public void executeDefault() {
+        TranslationsGatherer gatherer = new TranslationsGatherer();
         NestedTagValue translationValuesHolder = new NestedTagValue();
 
         for (TranslationInfo translation : gatherer.getTranslationInfo()) {

src/test/java/tools/docs/translations/TranslationsGatherer.java

@@ -11,6 +11,8 @@ import java.util.List;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import static tools.utils.FileIoUtils.listFilesOrThrow;
+
 /**
  * Gathers all available translations of AuthMe.
  */
@@ -31,10 +33,7 @@ public class TranslationsGatherer {
     }
 
     private void gatherTranslations() {
-        File[] files = new File(MESSAGES_FOLDER).listFiles();
-        if (files == null) {
-            throw new IllegalStateException("Cannot read files of '" + MESSAGES_FOLDER + "'");
-        }
+        File[] files = listFilesOrThrow(new File(MESSAGES_FOLDER));
         for (File file : files) {
             String code = getLanguageCode(file.getName());
             if (code != null) {

src/test/java/tools/helptranslation/VerifyHelpTranslations.java

@@ -10,6 +10,8 @@ import java.util.Scanner;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
+import static tools.utils.FileIoUtils.listFilesOrThrow;
+
 /**
  * Verifies the help translations for validity and completeness.
  */
@@ -57,10 +59,7 @@ public class VerifyHelpTranslations implements ToolTask {
     }
 
     private static List<File> getHelpTranslations() {
-        File[] files = new File(FOLDER).listFiles();
-        if (files == null) {
-            throw new IllegalStateException("Could not get files from '" + FOLDER + "'");
-        }
+        File[] files = listFilesOrThrow(new File(FOLDER));
         List<File> helpFiles = Arrays.stream(files)
             .filter(file -> HELP_MESSAGE_PATTERN.matcher(file.getName()).matches())
             .collect(Collectors.toList());

src/test/java/tools/messages/VerifyMessagesTask.java

@@ -17,6 +17,8 @@ import java.util.Set;
 import java.util.regex.Pattern;
 import java.util.stream.Collectors;
 
+import static tools.utils.FileIoUtils.listFilesOrThrow;
+
 /**
  * Task to verify the keys in the messages files.
  */
@@ -124,12 +126,7 @@ public final class VerifyMessagesTask implements ToolTask {
     }
 
     private static List<File> getMessagesFiles() {
-        File folder = new File(MESSAGES_FOLDER);
-        File[] files = folder.listFiles();
-        if (files == null) {
-            throw new IllegalStateException("Could not read files from folder '" + folder.getName() + "'");
-        }
-
+        File[] files = listFilesOrThrow(new File(MESSAGES_FOLDER));
         List<File> messageFiles = new ArrayList<>();
         for (File file : files) {
             if (MESSAGE_FILE_PATTERN.matcher(file.getName()).matches()) {

src/test/java/tools/messages/translation/WriteAllExportsTask.java

@@ -8,6 +8,8 @@ import tools.utils.ToolsConstants;
 import java.io.File;
 import java.util.Scanner;
 
+import static tools.utils.FileIoUtils.listFilesOrThrow;
+
 /**
  * Task which exports all messages to a local folder.
  */
@@ -22,11 +24,7 @@ public class WriteAllExportsTask extends ExportMessagesTask {
 
     @Override
     public void execute(Scanner scanner) {
-        File[] messageFiles = new File(MESSAGES_FOLDER).listFiles();
-        if (messageFiles == null || messageFiles.length == 0) {
-            throw new IllegalStateException("Could not read messages folder");
-        }
-
+        final File[] messageFiles = listFilesOrThrow(new File(MESSAGES_FOLDER));
         final FileConfiguration defaultMessages = loadDefaultMessages();
         for (File file : messageFiles) {
             String code = file.getName().substring("messages_".length(), file.getName().length() - ".yml".length());

src/test/java/tools/utils/FileIoUtils.java

@@ -1,5 +1,6 @@
 package tools.utils;
 
+import java.io.File;
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
@@ -62,4 +63,19 @@ public final class FileIoUtils {
         }
     }
 
+    /**
+     * Returns a folder's files or throws an exception if the folder could not be read or if it is empty.
+     *
+     * @param folder the folder to read
+     * @return the files in the folder
+     */
+    public static File[] listFilesOrThrow(File folder) {
+        File[] files = folder.listFiles();
+        if (files == null) {
+            throw new IllegalStateException("Could not read folder '" + folder + "'");
+        } else if (files.length == 0) {
+            throw new IllegalStateException("Folder '" + folder + "' is empty");
+        }
+        return files;
+    }
 }