perf(api): initialize StringBuilder with specified capacities for performance

backend/src/main/java/org/booklore/app/service/AppBookService.java

@@ -1168,7 +1168,7 @@ private List<AppFilterOptions.CountedOption> queryCountedOptions(
     }
 
     private String buildScopeClause(String libraryClause, String shelfClause, String magicBookClause) {
-        var sb = new StringBuilder();
+        var sb = new StringBuilder(128);
         if (!libraryClause.isEmpty()) sb.append(" ").append(libraryClause);
         if (!shelfClause.isEmpty()) sb.append(" ").append(shelfClause);
         if (!magicBookClause.isEmpty()) sb.append(" ").append(magicBookClause);

backend/src/main/java/org/booklore/controller/OidcAuthController.java

@@ -98,7 +98,7 @@ public ResponseEntity<Void> handleRedirect(
                 throw ApiError.GENERIC_UNAUTHORIZED.createException("Failed to obtain tokens");
             }
 
-            StringBuilder fragment = new StringBuilder();
+            StringBuilder fragment = new StringBuilder(256);
             fragment.append("access_token=").append(URLEncoder.encode(tokens.get("accessToken"), StandardCharsets.UTF_8));
             fragment.append("&refresh_token=").append(URLEncoder.encode(tokens.get("refreshToken"), StandardCharsets.UTF_8));
 

backend/src/main/java/org/booklore/service/InstallationService.java

@@ -80,7 +80,7 @@ private String hashToSha256(String input) {
         try {
             MessageDigest digest = MessageDigest.getInstance("SHA-256");
             byte[] hash = digest.digest(input.getBytes(StandardCharsets.UTF_8));
-            StringBuilder hexString = new StringBuilder();
+            StringBuilder hexString = new StringBuilder(64);
             for (byte b : hash) {
                 String hex = Integer.toHexString(0xff & b);
                 if (hex.length() == 1) hexString.append('0');

backend/src/main/java/org/booklore/service/bookdrop/FilenamePatternExtractor.java

@@ -254,7 +254,7 @@ private ParsedPattern parsePattern(String pattern) {
         }
 
         List<PlaceholderMatch> placeholderMatches = findAllPlaceholders(pattern);
-        StringBuilder regexBuilder = new StringBuilder();
+        StringBuilder regexBuilder = new StringBuilder(256);
         List<String> placeholderOrder = new ArrayList<>();
         int lastEnd = 0;
 
@@ -327,7 +327,7 @@ private List<PlaceholderMatch> findAllPlaceholders(String pattern) {
     }
 
     private String buildRegexForDateFormat(String dateFormat) {
-        StringBuilder result = new StringBuilder();
+        StringBuilder result = new StringBuilder(64);
         int i = 0;
 
         while (i < dateFormat.length()) {

backend/src/main/java/org/booklore/service/metadata/CoverImageGenerator.java

@@ -413,7 +413,7 @@ private void renderAuthor(Graphics2D g, String author, Palette p, int w, int h,
         int bottomBound = h - margin;
 
         String[] authors = author.split(",");
-        StringBuilder formattedAuthors = new StringBuilder();
+        StringBuilder formattedAuthors = new StringBuilder(128);
         for (int i = 0; i < authors.length; i++) {
             if (i > 0) formattedAuthors.append("\n").append(authors[i].trim());
             else formattedAuthors.append(authors[i].trim());
@@ -642,13 +642,13 @@ private Font resolveFont(Graphics2D g, String text, int maxW, int startSize, int
 
     private List<String> wrapText(String text, FontMetrics fm, int maxW, int maxLines) {
         List<String> lines = new ArrayList<>();
-        StringBuilder cur = new StringBuilder();
+        StringBuilder cur = new StringBuilder(32);
 
         for (String word : WS.split(text.trim())) {
             if (fm.stringWidth(word) > maxW) {
                 if (!cur.isEmpty()) {
                     lines.add(cur.toString().trim());
-                    cur = new StringBuilder();
+                    cur.setLength(0);
                 }
                 lines.addAll(breakWord(word, fm, maxW));
                 continue;
@@ -660,7 +660,8 @@ private List<String> wrapText(String text, FontMetrics fm, int maxW, int maxLine
                 cur.append(" ").append(word);
             } else {
                 lines.add(cur.toString().trim());
-                cur = new StringBuilder(word);
+                cur.setLength(0);
+                cur.append(word);
             }
         }
 
@@ -679,12 +680,12 @@ private List<String> wrapText(String text, FontMetrics fm, int maxW, int maxLine
 
     private List<String> breakWord(String word, FontMetrics fm, int maxW) {
         List<String> parts = new ArrayList<>();
-        StringBuilder cur = new StringBuilder();
+        StringBuilder cur = new StringBuilder(32);
 
         for (char c : word.toCharArray()) {
             if (fm.stringWidth(cur.toString() + c) > maxW && !cur.isEmpty()) {
                 parts.add(cur.toString());
-                cur = new StringBuilder();
+                cur.setLength(0);
             }
             cur.append(c);
         }

backend/src/main/java/org/booklore/service/metadata/extractor/AudiobookMetadataExtractor.java

@@ -357,7 +357,7 @@ private List<AudiobookMetadata.ChapterInfo> extractChaptersWithFfprobe(File audi
             pb.redirectErrorStream(true);
 
             Process process = pb.start();
-            StringBuilder output = new StringBuilder();
+            StringBuilder output = new StringBuilder(4096);
 
             try (BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()))) {
                 String line;

backend/src/main/java/org/booklore/service/metadata/extractor/Fb2MetadataExtractor.java

@@ -291,7 +291,7 @@ private String extractPersonName(Element personElement) {
     }
 
     private String extractTextFromElement(Element element) {
-        StringBuilder text = new StringBuilder();
+        StringBuilder text = new StringBuilder(1024);
         NodeList children = element.getChildNodes();
 
         for (int i = 0; i < children.getLength(); i++) {

backend/src/main/java/org/booklore/service/metadata/parser/GoogleParser.java

@@ -513,7 +513,7 @@ private String getSearchTerm(Book book, FetchMetadataRequest request) {
 
     private String truncateToMaxWords(String input) {
         String[] words = WHITESPACE_PATTERN.split(input);
-        StringBuilder truncated = new StringBuilder();
+        StringBuilder truncated = new StringBuilder(60);
 
         for (String word : words) {
             if (truncated.length() + word.length() + 1 > MAX_SEARCH_TERM_LENGTH) {

backend/src/main/java/org/booklore/service/metadata/writer/CbxMetadataWriter.java

@@ -246,7 +246,7 @@ private void applyMetadataChanges(ComicInfo info, BookMetadataEntity metadata, M
         info.setWeb(primaryUrl);
 
         // Notes - Custom Metadata
-        StringBuilder notesBuilder = new StringBuilder();
+        StringBuilder notesBuilder = new StringBuilder(1024);
         String existingNotes = info.getNotes();
 
         // Preserve existing notes that don't start with [BookLore

backend/src/main/java/org/booklore/service/metadata/writer/PdfMetadataWriter.java

@@ -126,7 +126,7 @@ private void applyMetadataToDocument(PdfDocument doc, BookMetadataEntity entity,
         MetadataCopyHelper helper = new MetadataCopyHelper(entity);
 
         // --- PDF Info Dictionary (legacy) via PDFium4j ---
-        StringBuilder keywordsBuilder = new StringBuilder();
+        StringBuilder keywordsBuilder = new StringBuilder(256);
         helper.copyCategories(clear != null && clear.isCategories(), cats -> {
             if (cats != null && !cats.isEmpty()) {
                 keywordsBuilder.append(String.join("; ", cats));
@@ -326,7 +326,7 @@ private void addBookloreRating(Map<String, String> customFields, String prefix,
      * insert them as a separate rdf:Description block before &lt;/rdf:RDF&gt;.
      */
     private String injectBagElements(String xmpPacket, MetadataCopyHelper helper, MetadataClearFlags clear) {
-        StringBuilder bags = new StringBuilder();
+        StringBuilder bags = new StringBuilder(512);
 
         helper.copyTags(clear != null && clear.isTags(), tags -> {
             if (tags != null && !tags.isEmpty()) appendBagXml(bags, "tags", tags);

backend/src/main/java/org/booklore/service/reader/AudioFileUtilityService.java

@@ -102,11 +102,11 @@ private int naturalCompare(Path p1, Path p2) {
             char c2 = s2.charAt(i2);
 
             if (Character.isDigit(c1) && Character.isDigit(c2)) {
-                StringBuilder b1 = new StringBuilder();
+                StringBuilder b1 = new StringBuilder(10);
                 while (i1 < s1.length() && Character.isDigit(s1.charAt(i1))) {
                     b1.append(s1.charAt(i1++));
                 }
-                StringBuilder b2 = new StringBuilder();
+                StringBuilder b2 = new StringBuilder(10);
                 while (i2 < s2.length() && Character.isDigit(s2.charAt(i2))) {
                     b2.append(s2.charAt(i2++));
                 }

backend/src/main/java/org/booklore/util/Md5Util.java

@@ -16,7 +16,7 @@ public String md5Hex(String input) {
         try {
             MessageDigest md = MessageDigest.getInstance("MD5");
             byte[] digest = md.digest(input.getBytes(StandardCharsets.UTF_8));
-            StringBuilder sb = new StringBuilder();
+            StringBuilder sb = new StringBuilder(32);
             for (byte b : digest) {
                 sb.append(String.format("%02x", b));
             }