Introduced Optional return values (#1573)

* Introduced Optional return values
JabRef · Jul 12, 2016 · aa42800 · aa42800
1 parent eddf636
commit aa42800
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Showing 13 changed files with 92 additions and 100 deletions.
diff --git a/src/main/java/net/sf/jabref/JabRefPreferences.java b/src/main/java/net/sf/jabref/JabRefPreferences.java
@@ -36,6 +36,7 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.prefs.BackingStoreException;
 import java.util.prefs.InvalidPreferencesFormatException;
@@ -1013,10 +1014,10 @@ public List<String> getStringList(String key) {
 
         StringReader rd = new StringReader(names);
         List<String> res = new ArrayList<>();
-        String rs;
+        Optional<String> rs;
         try {
-            while ((rs = getNextUnit(rd)) != null) {
-                res.add(rs);
+            while ((rs = getNextUnit(rd)).isPresent()) {
+                res.add(rs.get());
             }
         } catch (IOException ignored) {
             // Ignored
@@ -1205,7 +1206,7 @@ private Object getObject(String key) {
     }
 
 
-    private static String getNextUnit(Reader data) throws IOException {
+    private static Optional<String> getNextUnit(Reader data) throws IOException {
         // character last read
         // -1 if end of stream
         // initialization necessary, because of Java compiler
@@ -1240,12 +1241,12 @@ private static String getNextUnit(Reader data) throws IOException {
             }
         }
         if (res.length() > 0) {
-            return res.toString();
+            return Optional.of(res.toString());
         } else if (c == -1) {
             // end of stream
-            return null;
+            return Optional.empty();
         } else {
-            return "";
+            return Optional.of("");
         }
     }
 
@@ -1265,22 +1266,22 @@ public void storeCustomEntryType(CustomEntryType tp, int number) {
     /**
      * Retrieves all information about the entry type in preferences, with the tag given by number.
      */
-    public CustomEntryType getCustomEntryType(int number) {
+    public Optional<CustomEntryType> getCustomEntryType(int number) {
         String nr = String.valueOf(number);
         String name = get(JabRefPreferences.CUSTOM_TYPE_NAME + nr);
         if (name == null) {
-            return null;
+            return Optional.empty();
         }
         List<String> req = getStringList(JabRefPreferences.CUSTOM_TYPE_REQ + nr);
         List<String> opt = getStringList(JabRefPreferences.CUSTOM_TYPE_OPT + nr);
         List<String> priOpt = getStringList(JabRefPreferences.CUSTOM_TYPE_PRIOPT + nr);
         if (priOpt.isEmpty()) {
-            return new CustomEntryType(EntryUtil.capitalizeFirst(name), req, opt);
+            return Optional.of(new CustomEntryType(EntryUtil.capitalizeFirst(name), req, opt));
         }
         List<String> secondary = new ArrayList<>(opt);
         secondary.removeAll(priOpt);
 
-        return new CustomEntryType(EntryUtil.capitalizeFirst(name), req, priOpt, secondary);
+        return Optional.of(new CustomEntryType(EntryUtil.capitalizeFirst(name), req, priOpt, secondary));
 
     }
 
@@ -1297,17 +1298,6 @@ public void purgeCustomEntryTypes(int number) {
         purgeSeries(JabRefPreferences.CUSTOM_TYPE_PRIOPT, number);
     }
 
-    public void purgeCustomEntryTypes() {
-        int number = 0;
-        if(getCustomEntryType(number) != null) {
-            number++;
-        }
-
-        for(int i = 0; i < number; i++) {
-            purgeCustomEntryTypes(i);
-        }
-    }
-
     /**
      * Removes all entries keyed by prefix+number, where number is equal to or higher than the given number.
      *

diff --git a/src/main/java/net/sf/jabref/MetaData.java b/src/main/java/net/sf/jabref/MetaData.java
@@ -85,9 +85,9 @@ private MetaData(Map<String, String> inData) throws ParseException {
             List<String> orderedData = new ArrayList<>();
             // We must allow for ; and \ in escape sequences.
             try {
-                String unit;
-                while ((unit = getNextUnit(data)) != null) {
-                    orderedData.add(unit);
+                Optional<String> unit;
+                while ((unit = getNextUnit(data)).isPresent()) {
+                    orderedData.add(unit.get());
                 }
             } catch (IOException ex) {
                 LOGGER.error("Weird error while parsing meta data.", ex);
@@ -200,7 +200,7 @@ public void setGroups(GroupTreeNode root) {
     /**
      * Reads the next unit. Units are delimited by ';'.
      */
-    private static String getNextUnit(Reader reader) throws IOException {
+    private static Optional<String> getNextUnit(Reader reader) throws IOException {
         int c;
         boolean escape = false;
         StringBuilder res = new StringBuilder();
@@ -217,9 +217,9 @@ private static String getNextUnit(Reader reader) throws IOException {
             }
         }
         if (res.length() > 0) {
-            return res.toString();
+            return Optional.of(res.toString());
         }
-        return null;
+        return Optional.empty();
     }
 
     public DBStrings getDBStrings() {

diff --git a/src/main/java/net/sf/jabref/bst/BibtexCaseChanger.java b/src/main/java/net/sf/jabref/bst/BibtexCaseChanger.java
@@ -280,7 +280,7 @@ private int convertCharIfBraceLevelIsZero(char[] c, int start, StringBuilder sb,
 
     /**
      * Determine whether there starts a special char at pos (e.g., oe, AE). Return it as string.
-     * If nothing found, return null
+     * If nothing found, return Optional.empty()
      *
      * Also used by BibtexPurify
      *

diff --git a/src/main/java/net/sf/jabref/gui/maintable/MainTableSelectionListener.java b/src/main/java/net/sf/jabref/gui/maintable/MainTableSelectionListener.java
@@ -50,7 +50,6 @@
 import net.sf.jabref.logic.l10n.Localization;
 import net.sf.jabref.logic.util.OS;
 import net.sf.jabref.model.entry.BibEntry;
-import net.sf.jabref.specialfields.SpecialField;
 import net.sf.jabref.specialfields.SpecialFieldValue;
 import net.sf.jabref.specialfields.SpecialFieldsUtils;
 
@@ -351,19 +350,20 @@ public void mouseClicked(MouseEvent e) {
      * @param columnName the name of the specialfield column
      */
     private void handleSpecialFieldLeftClick(MouseEvent e, String columnName) {
-        SpecialField field = SpecialFieldsUtils.getSpecialFieldInstanceFromFieldName(columnName);
-        if ((e.getClickCount() == 1) && (field != null)) {
-            // special field found
-            if (field.isSingleValueField()) {
-                // directly execute toggle action instead of showing a menu with one action
-                field.getValues().get(0).getAction(panel.frame()).action();
-            } else {
-                JPopupMenu menu = new JPopupMenu();
-                for (SpecialFieldValue val : field.getValues()) {
-                    menu.add(val.getMenuAction(panel.frame()));
+        if ((e.getClickCount() == 1)) {
+            SpecialFieldsUtils.getSpecialFieldInstanceFromFieldName(columnName).ifPresent(field -> {
+                // special field found
+                if (field.isSingleValueField()) {
+                    // directly execute toggle action instead of showing a menu with one action
+                    field.getValues().get(0).getAction(panel.frame()).action();
+                } else {
+                    JPopupMenu menu = new JPopupMenu();
+                    for (SpecialFieldValue val : field.getValues()) {
+                        menu.add(val.getMenuAction(panel.frame()));
+                    }
+                    menu.show(table, e.getX(), e.getY());
                 }
-                menu.show(table, e.getX(), e.getY());
-            }
+            });
         }
     }
 

diff --git a/src/main/java/net/sf/jabref/importer/fileformat/BibtexParser.java b/src/main/java/net/sf/jabref/importer/fileformat/BibtexParser.java
@@ -27,6 +27,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Optional;
 
 import net.sf.jabref.MetaData;
 import net.sf.jabref.importer.ParserResult;
@@ -280,12 +281,12 @@ private void parseJabRefComment(Map<String, String> meta) throws IOException {
                 .equals(CustomEntryType.ENTRYTYPE_FLAG)) {
             // A custom entry type can also be stored in a
             // "@comment"
-            CustomEntryType typ = CustomEntryType.parse(comment);
-            if(typ == null) {
+            Optional<CustomEntryType> typ = CustomEntryType.parse(comment);
+            if (typ.isPresent()) {
+                entryTypes.put(typ.get().getName(), typ.get());
+            } else {
                 parserResult.addWarning(Localization.lang("Ill-formed entrytype comment in bib file") + ": " +
                         comment);
-            } else {
-                entryTypes.put(typ.getName(), typ);
             }
 
             // custom entry types are always re-written by JabRef and not stored in the file

diff --git a/src/main/java/net/sf/jabref/logic/CustomEntryTypesManager.java b/src/main/java/net/sf/jabref/logic/CustomEntryTypesManager.java
@@ -3,6 +3,7 @@
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Optional;
 
 import net.sf.jabref.JabRefPreferences;
 import net.sf.jabref.model.EntryTypes;
@@ -19,10 +20,10 @@ public class CustomEntryTypesManager {
      */
     public static void loadCustomEntryTypes(JabRefPreferences prefs) {
         int number = 0;
-        CustomEntryType type;
-        while ((type = prefs.getCustomEntryType(number)) != null) {
-            EntryTypes.addOrModifyCustomEntryType(type);
-            ALL.add(type);
+        Optional<CustomEntryType> type;
+        while ((type = prefs.getCustomEntryType(number)).isPresent()) {
+            EntryTypes.addOrModifyCustomEntryType(type.get());
+            ALL.add(type.get());
             number++;
         }
     }

diff --git a/src/main/java/net/sf/jabref/logic/fulltext/MimeTypeDetector.java b/src/main/java/net/sf/jabref/logic/fulltext/MimeTypeDetector.java
@@ -3,6 +3,7 @@
 import java.io.IOException;
 import java.net.URL;
 import java.net.URLConnection;
+import java.util.Optional;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -11,19 +12,19 @@ public class MimeTypeDetector {
     private static final Log LOGGER = LogFactory.getLog(MimeTypeDetector.class);
 
     public static boolean isPdfContentType(String url) {
-        String contentType = getMimeType(url);
+        Optional<String> contentType = getMimeType(url);
 
-        return contentType != null && contentType.toLowerCase().startsWith("application/pdf");
+        return contentType.isPresent() && contentType.get().toLowerCase().startsWith("application/pdf");
     }
 
-    private static String getMimeType(String url) {
+    private static Optional<String> getMimeType(String url) {
         try {
             URLConnection connection = new URL(url).openConnection();
 
-            return connection.getContentType();
+            return Optional.ofNullable(connection.getContentType());
         } catch (IOException e) {
             LOGGER.debug("Error getting MIME type of URL", e);
-            return null;
+            return Optional.empty();
         }
     }
 }
diff --git a/src/main/java/net/sf/jabref/logic/xmp/XMPUtil.java b/src/main/java/net/sf/jabref/logic/xmp/XMPUtil.java
@@ -695,10 +695,8 @@ private static void writeToDCSchema(XMPSchemaDublinCore dcSchema,
                  *
                  * Bibtex-Fields used: year, month
                  */
-                String publicationDate = entry.getPublicationDate();
-                if (publicationDate != null) {
-                    dcSchema.addSequenceValue("dc:date", publicationDate);
-                }
+                entry.getPublicationDate()
+                        .ifPresent(publicationDate -> dcSchema.addSequenceValue("dc:date", publicationDate));
                 continue;
             }
             /**

diff --git a/src/main/java/net/sf/jabref/model/entry/AuthorListParser.java b/src/main/java/net/sf/jabref/model/entry/AuthorListParser.java
@@ -4,6 +4,7 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 
 public class AuthorListParser {
@@ -26,7 +27,7 @@ public class AuthorListParser {
     /** true if upper-case token, false if lower-case */
     private boolean tokenCase;
 
-    
+
     // Constant HashSet containing names of TeX special characters
     private static final Set<String> TEX_NAMES = new HashSet<>();
 
@@ -84,21 +85,18 @@ public AuthorList parse(String listOfNames) {
         // Parse author by author
         List<Author> authors = new ArrayList<>(5); // 5 seems to be reasonable initial size
         while (tokenStart < original.length()) {
-            Author author = getAuthor();
-            if (author != null) {
-                authors.add(author);
-            }
+            getAuthor().ifPresent(authors::add);
         }
         return new AuthorList(authors);
     }
 
     /**
      * Parses one author name and returns preformatted information.
      *
-     * @return Preformatted author name; <CODE>null</CODE> if author name is
+     * @return Preformatted author name; <CODE>Optional.empty()</CODE> if author name is
      * empty.
      */
-    private Author getAuthor() {
+    private Optional<Author> getAuthor() {
 
         List<Object> tokens = new ArrayList<>(); // initialization
         int vonStart = -1;
@@ -135,8 +133,8 @@ private Author getAuthor() {
                 }
                 if (vonStart < 0) {
                     if (!tokenCase) {
-                        int previousTermToken = tokens.size() - TOKEN_GROUP_LENGTH - TOKEN_GROUP_LENGTH + OFFSET_TOKEN_TERM;
-                        if(previousTermToken >= 0 && tokens.get(previousTermToken).equals('-')) {
+                        int previousTermToken = (tokens.size() - TOKEN_GROUP_LENGTH - TOKEN_GROUP_LENGTH) + OFFSET_TOKEN_TERM;
+                        if((previousTermToken >= 0) && tokens.get(previousTermToken).equals('-')) {
                             // We are in a first name which contained a hyphen
                             break;
                         }
@@ -156,7 +154,7 @@ private Author getAuthor() {
         // Second step: split name into parts (here: calculate indices
         // of parts in 'tokens' Vector)
         if (tokens.isEmpty()) {
-            return null; // no author information
+            return Optional.empty(); // no author information
         }
 
         // the following negatives indicate absence of the corresponding part
@@ -251,13 +249,13 @@ private Author getAuthor() {
                 false);
         String jrPart = jrPartStart < 0 ? null : concatTokens(tokens, jrPartStart, jrPartEnd, OFFSET_TOKEN, false);
 
-        if(firstPart != null && lastPart != null && lastPart.equals(lastPart.toUpperCase()) && lastPart.length() < 5) {
+        if((firstPart != null) && (lastPart != null) && lastPart.equals(lastPart.toUpperCase()) && (lastPart.length() < 5)) {
             // The last part is a small string in complete upper case, so interpret it as initial of the first name
             // This is the case for example in "Smith SH" which we think of as lastname=Smith and firstname=SH
             // The length < 5 constraint should allow for "Smith S.H." as input
-            return new Author(lastPart, lastPart, vonPart, firstPart, jrPart);
+            return Optional.of(new Author(lastPart, lastPart, vonPart, firstPart, jrPart));
         } else {
-            return new Author(firstPart, firstAbbr, vonPart, lastPart, jrPart);
+            return Optional.of(new Author(firstPart, firstAbbr, vonPart, lastPart, jrPart));
         }
     }
 
@@ -356,7 +354,7 @@ private int getToken() {
             if (c == '{') {
                 bracesLevel++;
             }
-            if (firstLetterIsFound && (tokenAbbr < 0) && (bracesLevel == 0 || c == '{')) {
+            if (firstLetterIsFound && (tokenAbbr < 0) && ((bracesLevel == 0) || (c == '{'))) {
                 tokenAbbr = tokenEnd;
             }
             if ((c == '}') && (bracesLevel > 0)) {

diff --git a/src/main/java/net/sf/jabref/model/entry/BibEntry.java b/src/main/java/net/sf/jabref/model/entry/BibEntry.java
@@ -497,17 +497,18 @@ public String getAuthorTitleYear(int maxCharacters) {
      *
      * @return will return the publication date of the entry or null if no year was found.
      */
-    public String getPublicationDate() {
+    public Optional<String> getPublicationDate() {
         if (!hasField("year")) {
-            return null;
+            return Optional.empty();
         }
 
-        String year = getField("year");
+        Optional<String> year = getFieldOptional("year");
 
-        if (hasField("month")) {
-            MonthUtil.Month month = MonthUtil.getMonth(getField("month"));
+        Optional<String> monthString = getFieldOptional("month");
+        if (monthString.isPresent()) {
+            MonthUtil.Month month = MonthUtil.getMonth(monthString.get());
             if (month.isValid()) {
-                return year + "-" + month.twoDigitNumber;
+                return Optional.of(year.orElse("") + "-" + month.twoDigitNumber);
             }
         }
         return year;