Optimize saving

CHANGELOG.md

@@ -69,6 +69,7 @@ Note that this project **does not** adhere to [Semantic Versioning](http://semve
 - We fixed an issue where Content selector does not seem to work for custom fields. [#6819](https://github.com/JabRef/jabref/issues/6819)
 - We fixed an issue in which a linked online file consisting of a web page was saved as an invalid pdf file upon being downloaded. The user is now notified when downloading a linked file results in an HTML file. [#7452](https://github.com/JabRef/jabref/issues/7452)
 - We fixed an issue where opening BibTex file (doubleclick) from Folder with spaces not working. [#6487](https://github.com/JabRef/jabref/issues/6487)
+- We fixed an issue with saving large `.bib` files [#7265](https://github.com/JabRef/jabref/issues/7265)
 
 ### Removed
 

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

@@ -4,6 +4,7 @@
 import java.time.Year;
 import java.time.YearMonth;
 import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeFormatterBuilder;
 import java.time.format.DateTimeParseException;
 import java.time.temporal.ChronoField;
 import java.time.temporal.TemporalAccessor;
@@ -15,6 +16,31 @@
 
 public class Date {
 
+    private static final DateTimeFormatter NORMALIZED_DATE_FORMATTER = DateTimeFormatter.ofPattern("uuuu[-MM][-dd]");
+    private static final DateTimeFormatter SIMPLE_DATE_FORMATS;
+    static {
+        List<String> formatStrings = Arrays.asList(
+                "uuuu-M-d",     // covers 2009-1-15
+                "uuuu-M",       // covers 2009-11
+                "d-M-uuuu",     // covers 15-1-2012
+                "M-uuuu",       // covers 1-2012
+                "M/uuuu",       // covers 9/2015 and 09/2015
+                "M/uu",         // covers 9/15
+                "MMMM d, uuuu", // covers September 1, 2015
+                "MMMM, uuuu",   // covers September, 2015
+                "d.M.uuuu",     // covers 15.1.2015
+                "uuuu.M.d",     // covers 2015.1.15
+                "uuuu",         // covers 2015
+                "MMM, uuuu");   // covers Jan, 2020
+
+        SIMPLE_DATE_FORMATS = formatStrings.stream()
+                                           .map(DateTimeFormatter::ofPattern)
+                                           .reduce(new DateTimeFormatterBuilder(),
+                                                   DateTimeFormatterBuilder::appendOptional,
+                                                   (builder, formatterBuilder) -> builder.append(formatterBuilder.toFormatter()))
+                                           .toFormatter(Locale.US);
+    }
+
     private final TemporalAccessor date;
 
     public Date(int year, int month, int dayOfMonth) {
@@ -33,43 +59,19 @@ public Date(TemporalAccessor date) {
         this.date = date;
     }
 
-    /**
-     * Try to parse the following formats
-     *  - "M/y" (covers 9/15, 9/2015, and 09/2015)
-     *  - "MMMM (dd), yyyy" (covers September 1, 2015 and September, 2015)
-     *  - "yyyy-MM-dd" (covers 2009-1-15)
-     *  - "dd-MM-yyyy" (covers 15-1-2009)
-     *  - "d.M.uuuu" (covers 15.1.2015)
-     *  - "uuuu.M.d" (covers 2015.1.15)
-     *  - "MMM, uuuu" (covers Jan, 2020)
-     * The code is essentially taken from http://stackoverflow.com/questions/4024544/how-to-parse-dates-in-multiple-formats-using-simpledateformat.
-     */
     public static Optional<Date> parse(String dateString) {
         Objects.requireNonNull(dateString);
-        List<String> formatStrings = Arrays.asList(
-                "uuuu-M-d",
-                "uuuu-M",
-                "d-M-uuuu",
-                "M-uuuu",
-                "M/uu",
-                "M/uuuu",
-                "MMMM d, uuuu",
-                "MMMM, uuuu",
-                "d.M.uuuu",
-                "uuuu.M.d", "uuuu",
-                "MMM, uuuu");
-
-        for (String formatString : formatStrings) {
-            try {
-                // Locale is required for parsing month names correctly. Currently this expects the month names to be in English
-                TemporalAccessor parsedDate = DateTimeFormatter.ofPattern(formatString).withLocale(Locale.US).parse(dateString);
-                return Optional.of(new Date(parsedDate));
-            } catch (DateTimeParseException ignored) {
-                // Ignored
-            }
+
+        if (dateString.isEmpty()) {
+            return Optional.empty();
         }
 
-        return Optional.empty();
+        try {
+            TemporalAccessor parsedDate = SIMPLE_DATE_FORMATS.parse(dateString);
+            return Optional.of(new Date(parsedDate));
+        } catch (DateTimeParseException ignored) {
+            return Optional.empty();
+        }
     }
 
     public static Optional<Date> parse(Optional<String> yearValue, Optional<String> monthValue,
@@ -105,8 +107,7 @@ private static Optional<Integer> convertToInt(String value) {
     }
 
     public String getNormalized() {
-        DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("uuuu[-MM][-dd]");
-        return dateFormatter.format(date);
+        return NORMALIZED_DATE_FORMATTER.format(date);
     }
 
     public Optional<Integer> getYear() {