Bump checkstyle from 8.19 to 8.20 (#4928)

* Bump checkstyle from 8.19 to 8.20

Bumps [checkstyle](https://github.com/checkstyle/checkstyle) from 8.19 to 8.20.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](checkstyle/checkstyle@checkstyle-8.19...checkstyle-8.20)

Signed-off-by: dependabot[bot] <support@dependabot.com>

* Fix checkstyle

* Fix checkstyle

build.gradle

@@ -173,7 +173,7 @@ dependencies {
     testCompile "org.testfx:testfx-core:4.0.+"
     testCompile "org.testfx:testfx-junit5:4.0.+"
 
-    checkstyle 'com.puppycrawl.tools:checkstyle:8.19'
+    checkstyle 'com.puppycrawl.tools:checkstyle:8.20'
 }
 
 jacoco {

src/main/java/org/jabref/gui/autocompleter/SuggestionProvider.java

@@ -29,7 +29,6 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
-import java.util.Collections;
 import java.util.Comparator;
 import java.util.HashSet;
 import java.util.List;
@@ -55,7 +54,6 @@ public abstract class SuggestionProvider<T> implements Callback<ISuggestionReque
     /**
      * Create a default suggestion provider based on the toString() method of the generic objects
      * @param possibleSuggestions All possible suggestions
-     * @return
      */
     public static <T> SuggestionProvider<T> create(Collection<T> possibleSuggestions) {
         return create(null, possibleSuggestions);
@@ -67,7 +65,6 @@ public static <T> SuggestionProvider<T> create(Collection<T> possibleSuggestions
      *
      * @param stringConverter A stringConverter which converts generic T into a string
      * @param possibleSuggestions All possible suggestions
-     * @return
      */
     public static <T> SuggestionProvider<T> create(Callback<T, String> stringConverter, Collection<T> possibleSuggestions) {
         SuggestionProviderString<T> suggestionProvider = new SuggestionProviderString<>(stringConverter);
@@ -77,15 +74,13 @@ public static <T> SuggestionProvider<T> create(Callback<T, String> stringConvert
 
     /**
      * Add the given new possible suggestions to this  SuggestionProvider
-     * @param newPossible
      */
     public void addPossibleSuggestions(@SuppressWarnings("unchecked") T... newPossible) {
         addPossibleSuggestions(Arrays.asList(newPossible));
     }
 
     /**
      * Add the given new possible suggestions to this  SuggestionProvider
-     * @param newPossible
      */
     public void addPossibleSuggestions(Collection<T> newPossible) {
         synchronized (possibleSuggestionsLock) {
@@ -113,39 +108,21 @@ public final Collection<T> call(final ISuggestionRequest request) {
                     }
                 }
             }
-            Collections.sort(suggestions, getComparator());
+            suggestions.sort(getComparator());
         }
         return suggestions;
     }
 
-
-    /***************************************************************************
-     *                                                                         *
-     * Static methods                                                          *
-     *                                                                         *
-     **************************************************************************/
-
     /**
      * Get the comparator to order the suggestions
-     * @return
      */
     protected abstract Comparator<T> getComparator();
 
     /**
      * Check the given possible suggestion is a match (is a valid suggestion)
-     * @param suggestion
-     * @param request
-     * @return
      */
     protected abstract boolean isMatch(T suggestion, ISuggestionRequest request);
 
-
-    /***************************************************************************
-     *                                                                         *
-     * Default implementations                                                 *
-     *                                                                         *
-     **************************************************************************/
-
     /**
      * This is a simple string based suggestion provider.
      * All generic suggestions T are turned into strings for processing.
@@ -166,18 +143,14 @@ public int compare(T o1, T o2) {
 
         /**
          * Create a new SuggestionProviderString
-         * @param stringConverter
          */
         public SuggestionProviderString(Callback<T, String> stringConverter) {
             this.stringConverter = stringConverter;
 
             // In case no stringConverter was provided, use the default strategy
             if (this.stringConverter == null) {
-                this.stringConverter = new Callback<T, String>() {
-                    @Override
-                    public String call(T obj) {
-                        return obj != null ? obj.toString() : ""; //$NON-NLS-1$
-                    }
+                this.stringConverter = obj -> {
+                    return obj != null ? obj.toString() : ""; //$NON-NLS-1$
                 };
             }
         }

src/main/java/org/jabref/gui/collab/DatabaseChangeViewModel.java

@@ -31,7 +31,6 @@ public void setAccepted(boolean a) {
         accepted = a;
     }
 
-
     /**
      * This method returns a JComponent detailing the nature of the change.
      * @return JComponent

src/main/java/org/jabref/gui/customentrytypes/FieldSetComponent.java

@@ -324,7 +324,6 @@ private void move(int dy) {
         list.setSelectedIndex(newInd);
     }
 
-
     /**
      * FocusListener to select the first entry in the list of fields when they are focused
      */

src/main/java/org/jabref/gui/journals/ManageJournalAbbreviationsView.java

@@ -188,7 +188,6 @@ private void saveAbbreviationsAndCloseDialog() {
         close();
     }
 
-
     /**
      * This class provides a editable text field that is used as table cell.
      * It handles the editing of the name column.

src/main/java/org/jabref/gui/search/SearchWorker.java

@@ -18,26 +18,21 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-
 /**
  * Not reusable. Always create a new instance for each search!
  */
 class SearchWorker extends SwingWorker<List<BibEntry>, Void> {
 
     private static final Logger LOGGER = LoggerFactory.getLogger(SearchWorker.class);
 
-    private final BasePanel basePanel;
     private final BibDatabase database;
 
     private final SearchQuery searchQuery;
-    private final SearchDisplayMode searchDisplayMode;
 
     public SearchWorker(BasePanel basePanel, SearchQuery searchQuery, SearchDisplayMode searchDisplayMode) {
-        this.basePanel = Objects.requireNonNull(basePanel);
         this.database = Objects.requireNonNull(basePanel.getDatabase());
         this.searchQuery = Objects.requireNonNull(searchQuery);
-        this.searchDisplayMode = Objects.requireNonNull(searchDisplayMode);
-        LOGGER.debug("Search (" + this.searchDisplayMode.getDisplayName() + "): " + this.searchQuery);
+        LOGGER.debug("Search (" + searchDisplayMode.getDisplayName() + "): " + this.searchQuery);
     }
 
     @Override

src/main/java/org/jabref/gui/util/TooltipTextUtil.java

@@ -52,7 +52,6 @@ public static String textToHTMLString(Text text) {
         return textString;
     }
 
-
     /**
      * Formats a String to multiple Texts by replacing some parts and adding font characteristics.
      */

src/main/java/org/jabref/gui/util/component/Tag.java

@@ -14,7 +14,6 @@
 import com.airhacks.afterburner.views.ViewLoader;
 import org.fxmisc.easybind.EasyBind;
 
-
 /**
  * A tag item in a {@link TagBar}.
  */

src/main/java/org/jabref/logic/bibtex/DuplicateCheck.java

@@ -316,8 +316,7 @@ public static double correlateByWords(final String s1, final String s2) {
         return 1 - missRate;
     }
 
-
-    /*
+    /**
      * Calculates the similarity (a number within 0 and 1) between two strings.
      * http://stackoverflow.com/questions/955110/similarity-string-comparison-in-java
      */

src/main/java/org/jabref/logic/bst/BibtexCaseChanger.java

@@ -48,7 +48,6 @@ public char asChar() {
             return asChar;
         }
 
-
         /**
          * Convert bstFormat char into ENUM
          *
@@ -72,7 +71,6 @@ private BibtexCaseChanger() {
      *
      * @param s the string to handle
      * @param format the format
-     * @return
      */
     public static String changeCase(String s, FORMAT_MODE format) {
         return (new BibtexCaseChanger()).doChangeCase(s, format);

src/main/java/org/jabref/logic/bst/VM.java

@@ -935,8 +935,6 @@ private void read() {
      * override any definition you define using this command. If you want to
      * define a string the user can't touch, use the FUNCTION command, which has
      * a compatible syntax.
-     *
-     * @param child
      */
     private void macro(Tree child) {
         String name = child.getChild(0).getText();
@@ -959,8 +957,7 @@ public void execute(BstEntry context) {
         }
     }
 
-
-    /*
+    /**
      * Declares the fields and entry variables. It has three arguments, each a
      * (possibly empty) list of variable names. The three lists are of: fields,
      * integer entry variables, and string entry variables. There is an

src/main/java/org/jabref/logic/citationstyle/CitationStyleCache.java

@@ -12,7 +12,6 @@
 import com.google.common.cache.LoadingCache;
 import com.google.common.eventbus.Subscribe;
 
-
 /**
  * Caches the generated Citations for quicker access
  * {@link CitationStyleGenerator} generates the citation with JavaScript which may take some time

src/main/java/org/jabref/logic/citationstyle/CitationStyleGenerator.java

@@ -11,7 +11,6 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-
 /**
  * Facade to unify the access to the citation style engine. Use these methods if you need rendered BibTeX item(s) in a
  * given journal style. This class uses {@link CSLAdapter} to create output.

src/main/java/org/jabref/logic/exporter/ModsExporter.java

@@ -48,13 +48,12 @@
 import org.jabref.model.entry.BibEntry;
 import org.jabref.model.entry.FieldName;
 
-
 /**
  * TemplateExporter for exporting in MODS XML format.
  */
 class ModsExporter extends Exporter {
 
-    protected static final String MODS_NAMESPACE_URI = "http://www.loc.gov/mods/v3";
+    private static final String MODS_NAMESPACE_URI = "http://www.loc.gov/mods/v3";
     private static final String MINUS = "-";
     private static final String DOUBLE_MINUS = "--";
     private static final String MODS_SCHEMA_LOCATION = "http://www.loc.gov/standards/mods/v3/mods-3-6.xsd";
@@ -320,7 +319,7 @@ private void handleAuthors(ModsDefinition mods, String value) {
                 name.getNamePartOrDisplayFormOrAffiliation().add(element);
 
                 //now take care of the forenames
-                String forename = author.substring(commaIndex + 1, author.length());
+                String forename = author.substring(commaIndex + 1);
                 String[] forenames = forename.split(" ");
                 for (String given : forenames) {
                     if (!given.isEmpty()) {

src/main/java/org/jabref/logic/importer/fetcher/MedlineFetcher.java

@@ -52,7 +52,6 @@ public class MedlineFetcher implements IdBasedParserFetcher, SearchBasedFetcher
 
     private int numberOfResultsFound;
 
-
     /**
      * Replaces all commas in a given string with " AND "
      *

src/main/java/org/jabref/logic/openoffice/OOBibStyle.java

@@ -730,7 +730,6 @@ private String getCitationMarkerField(BibEntry entry, BibDatabase database, Stri
         return "";
     }
 
-
     /**
      * Look up the nth author and return the proper last name for citation markers.
      *

src/main/java/org/jabref/logic/pdf/EntryAnnotationImporter.java

@@ -12,7 +12,6 @@
 import org.jabref.model.metadata.FilePreferences;
 import org.jabref.model.pdf.FileAnnotation;
 
-
 /**
  * Here all PDF files attached to a BibEntry are scanned for annotations using a PdfAnnotationImporter.
  */

src/main/java/org/jabref/logic/shared/DBMSProcessor.java

@@ -129,7 +129,6 @@ public void setupSharedDatabase() throws SQLException {
      */
     abstract String escape(String expression);
 
-
     /**
      * Inserts the given bibEntry into shared database.
      *

src/main/java/org/jabref/logic/shared/exception/NotASharedDatabaseException.java

@@ -1,6 +1,5 @@
 package org.jabref.logic.shared.exception;
 
-
 /**
  * This exception is thrown when a shared database is required, but it actually isn't one.
  */

src/main/java/org/jabref/logic/undo/UndoChangeEvent.java

@@ -43,7 +43,6 @@ public boolean isCanRedo() {
         return canRedo;
     }
 
-
     /**
     *
     * @return A description of the action to be redone

src/main/java/org/jabref/logic/util/Version.java

@@ -144,7 +144,6 @@ public boolean isNewerThan(Version otherVersion) {
         return false;
     }
 
-
     /**
      * Checks if this version should be updated to one of the given ones.
      * Ignoring the other Version if this one is Stable and the other one is not.

src/main/java/org/jabref/logic/util/io/FileUtil.java

@@ -53,7 +53,6 @@ public static Optional<String> getFileExtension(String fileName) {
         }
     }
 
-
     /**
      * Returns the extension of a file or Optional.empty() if the file does not have one (no . in name).
      *

src/main/java/org/jabref/model/cleanup/Formatter.java

@@ -18,7 +18,6 @@ public abstract class Formatter {
      */
     public abstract String getName();
 
-
     /**
      * Returns a unique key for the formatter that can be used for its identification
      * @return the key of the formatter, always not null

src/main/java/org/jabref/model/database/DuplicationChecker.java

@@ -19,11 +19,10 @@ public class DuplicationChecker {
     /** use a map instead of a set since I need to know how many of each key is in there */
     private final Map<String, Integer> allKeys = new HashMap<>();
 
-
     /**
      * Checks if there is more than one occurrence of this key
      */
-    public boolean isDuplicateCiteKeyExisting(String citeKey) {
+    private boolean isDuplicateCiteKeyExisting(String citeKey) {
         return getNumberOfKeyOccurrences(citeKey) > 1;
     }
 

src/main/java/org/jabref/model/entry/Month.java

@@ -38,7 +38,6 @@ public enum Month {
         this.number = number;
     }
 
-
     /**
      * Find month by one-based number.
      * If the number is not in the valid range, then an empty Optional is returned.

src/main/java/org/jabref/model/entry/specialfields/SpecialField.java

@@ -99,7 +99,6 @@ public static Optional<SpecialField> getSpecialFieldInstanceFromFieldName(String
         }
     }
 
-
     /**
      * @param fieldName the name of the field to check
      * @return true if given field is a special field, false otherwise