Refactor MagicEntryParser and address several PMD issues

pom.xml

@@ -171,6 +171,17 @@
 					<useSystemClassLoader>false</useSystemClassLoader>
 				</configuration>
 			</plugin>
+			<!-- build: add PMD Maven plugin for static code analysis -->
+			<plugin>
+				<groupId>org.apache.maven.plugins</groupId>
+				<artifactId>maven-pmd-plugin</artifactId>
+				<version>3.21.2</version>
+				<configuration>
+					<linkXRef>false</linkXRef>
+					<minimumTokens>100</minimumTokens>
+					<targetJdk>1.8</targetJdk> </configuration>
+			</plugin>
+			<!-- build: add PMD Maven plugin for static code analysis -->
 			<plugin>
 				<groupId>org.apache.maven.plugins</groupId>
 				<artifactId>maven-antrun-plugin</artifactId>

src/main/java/com/j256/simplemagic/ContentInfoInputStreamWrapper.java

@@ -67,7 +67,7 @@ public int read() throws IOException {
 	}
 
 	@Override
-	public int read(byte b[], int off, int len) throws IOException {
+	public int read(byte[] b, int off, int len) throws IOException {
 		int numRead = delegate.read(b, off, len);
 		int left = firstBytes.length - byteCount;
 		if (left > numRead) {

src/main/java/com/j256/simplemagic/ContentInfoUtil.java

@@ -50,7 +50,7 @@ public class ContentInfoUtil {
 	public final static int DEFAULT_READ_SIZE = 10 * 1024;
 
 	/** internal entries loaded once if the {@link ContentInfoUtil#MagicUtil()} constructor is used. */
-	private static MagicEntries internalMagicEntries;
+	private static volatile MagicEntries internalMagicEntries;
 
 	private final MagicEntries magicEntries;
 	private int fileReadSize = DEFAULT_READ_SIZE;
@@ -76,14 +76,19 @@ public ContentInfoUtil() {
 	 */
 	public ContentInfoUtil(ErrorCallBack errorCallBack) {
 		if (internalMagicEntries == null) {
-			try {
-				internalMagicEntries = readEntriesFromResource(INTERNAL_MAGIC_FILE, errorCallBack);
-			} catch (IOException e) {
-				throw new IllegalStateException(
-						"Could not load entries from internal magic file: " + INTERNAL_MAGIC_FILE, e);
-			}
-			if (internalMagicEntries == null) {
-				throw new IllegalStateException("Internal magic file not found in class-path: " + INTERNAL_MAGIC_FILE);
+			synchronized (ContentInfoUtil.class) {
+				if (internalMagicEntries == null) {
+					try {
+						internalMagicEntries = readEntriesFromResource(INTERNAL_MAGIC_FILE, errorCallBack);
+					} catch (IOException e) {
+						throw new IllegalStateException(
+								"Could not load entries from internal magic file: " + INTERNAL_MAGIC_FILE, e);
+					}
+					if (internalMagicEntries == null) {
+						throw new IllegalStateException(
+								"Internal magic file not found in class-path: " + INTERNAL_MAGIC_FILE);
+					}
+				}
 			}
 		}
 		this.magicEntries = internalMagicEntries;
@@ -328,7 +333,7 @@ public void setErrorCallBack(ErrorCallBack errorCallBack) {
 	}
 
 	private MagicEntries readEntriesFromFile(File fileOrDirectory, ErrorCallBack errorCallBack)
-			throws FileNotFoundException, IOException {
+			throws IOException {
 		if (fileOrDirectory.isFile()) {
 			FileReader reader = new FileReader(fileOrDirectory);
 			try {
@@ -337,13 +342,19 @@ private MagicEntries readEntriesFromFile(File fileOrDirectory, ErrorCallBack err
 				closeQuietly(reader);
 			}
 		} else if (fileOrDirectory.isDirectory()) {
-			MagicEntries entries = new MagicEntries();
-			for (File subFile : fileOrDirectory.listFiles()) {
+		MagicEntries entries = new MagicEntries();
+		File[] subFiles = fileOrDirectory.listFiles();
+		if (subFiles == null) {
+			return null;
+		}
+		for (File subFile : subFiles) {
 				FileReader fr = new FileReader(subFile);
 				try {
 					readEntries(entries, fr, errorCallBack);
 				} catch (IOException e) {
-					// ignore the file
+					if (errorCallBack != null) {
+						errorCallBack.error(subFile.getPath(), "could not read magic file: " + e.getMessage(), e);
+					}
 				} finally {
 					closeQuietly(fr);
 				}
@@ -418,6 +429,6 @@ public interface ErrorCallBack {
 		 * @param e
 		 *            Exception that was thrown trying to parse the line or null if none.
 		 */
-		public void error(String line, String details, Exception e);
+		void error(String line, String details, Exception e);
 	}
 }

src/main/java/com/j256/simplemagic/ContentType.java

@@ -912,7 +912,7 @@ public enum ContentType {
 	private final String[] fileExtensions;
 	private final IanaEntry ianaEntry;
 
-	private ContentType(String mimeType, String simpleName, String... fileExtensions) {
+	ContentType(String mimeType, String simpleName, String... fileExtensions) {
 		this.mimeType = mimeType;
 		this.simpleName = simpleName;
 		this.fileExtensions = fileExtensions;

src/main/java/com/j256/simplemagic/endian/EndianType.java

@@ -19,7 +19,7 @@ public enum EndianType {
 	// end
 	;
 
-	private EndianConverter converter;
+	private final EndianConverter converter;
 
 	private EndianType(EndianConverter converter) {
 		this.converter = converter;

src/main/java/com/j256/simplemagic/endian/MiddleEndianConverter.java

@@ -26,7 +26,7 @@ public byte[] convertToByteArray(long value, int size) {
 		if (size == 4) {
 			// BADC again
 			return new byte[] { (byte) ((value >> 16) & 0XFF), (byte) ((value >> 24) & 0XFF),
-					(byte) ((value >> 0) & 0XFF), (byte) ((value >> 8) & 0XFF) };
+					(byte) ((value) & 0XFF), (byte) ((value >> 8) & 0XFF) };
 		} else {
 			return null;
 		}

src/main/java/com/j256/simplemagic/entries/IanaEntries.java

@@ -112,8 +112,9 @@ private void closeQuietly(Closeable closeable) {
 		if (closeable != null) {
 			try {
 				closeable.close();
-			} catch (IOException e) {
-				// ignored
+			} catch (IOException ignored) {
+				// Intentionally ignored because this method is used only for cleanup.
+				// A failure while closing should not affect the main operation.
 			}
 		}
 	}

src/main/java/com/j256/simplemagic/entries/MagicEntries.java

@@ -37,7 +37,7 @@ public void readEntries(BufferedReader lineReader, ErrorCallBack errorCallBack)
 				break;
 			}
 			// skip blanks and comments
-			if (line.length() == 0 || line.charAt(0) == '#') {
+			if (line.isEmpty() || line.charAt(0) == '#') {
 				continue;
 			}
 

src/main/java/com/j256/simplemagic/entries/MagicEntry.java

@@ -63,7 +63,7 @@ public class MagicEntry {
 	 */
 	ContentInfo matchBytes(byte[] bytes) {
 		ContentData data = matchBytes(bytes, 0, 0, null);
-		if (data == null || data.name == MagicEntryParser.UNKNOWN_NAME) {
+		if (data == null || MagicEntryParser.UNKNOWN_NAME.equals(data.name)) {
 			return null;
 		} else {
 			return new ContentInfo(data.name, data.mimeType, data.sb.toString(), data.partial);
@@ -197,7 +197,7 @@ private ContentData matchBytes(byte[] bytes, int prevOffset, int level, ContentD
 		 * NOTE: the children will have the first opportunity to set this which makes sense since they are the most
 		 * specific.
 		 */
-		if (name != MagicEntryParser.UNKNOWN_NAME && contentData.name == MagicEntryParser.UNKNOWN_NAME) {
+		if (!MagicEntryParser.UNKNOWN_NAME.equals(name) && MagicEntryParser.UNKNOWN_NAME.equals(contentData.name)) {
 			contentData.name = name;
 		}
 		/*
@@ -216,12 +216,22 @@ private ContentData matchBytes(byte[] bytes, int prevOffset, int level, ContentD
 	 * Internal processing data about the content.
 	 */
 	static class ContentData {
-		String name;
-		boolean partial;
-		String mimeType;
-		int mimeTypeLevel;
+		private String name;
+		private boolean partial;
+		private String mimeType;
+		private int mimeTypeLevel;
 		final StringBuilder sb = new StringBuilder();
 
+		// add package-private getters/setters used within the entries package
+		String getName() { return name; }
+		void setName(String name) { this.name = name; }
+		boolean isPartial() { return partial; }
+		void setPartial(boolean partial) { this.partial = partial; }
+		String getMimeType() { return mimeType; }
+		void setMimeType(String mimeType) { this.mimeType = mimeType; }
+		int getMimeTypeLevel() { return mimeTypeLevel; }
+		void setMimeTypeLevel(int level) { this.mimeTypeLevel = level; }
+
 		private ContentData(String name, String mimeType, int mimeTypeLevel) {
 			this.name = name;
 			this.mimeType = mimeType;