Refactor synchronisation to InvertedIndex to make it threadsafe

Author: ntsh

src/main/java/in/ntsh/FileSearchEngine/DirectoryIndexer.java

@@ -14,8 +14,7 @@
 public class DirectoryIndexer {
 
 	private final Path path;
-	private InvertedIndex index = new InvertedIndex();
-	private final Object lock = new Object();
+	private InvertedIndex index;
 
 	/**
 	 * @param directoryPath : path of the directory to be indexed
@@ -45,15 +44,9 @@ private void indexFile(final Path file) {
 		try (Stream<String> lines = Files.lines(file)) { // Get all lines
 			lines.flatMap(Pattern.compile("\\W+")::splitAsStream) // Get all words
 			.map(word -> word.toLowerCase())
-			.forEach(word -> this.indexWordForFile(word, file.toString())); // index word
+			.forEach(word -> this.index.indexWordInFile(word, file.toString())); // index word
 		} catch (final Exception e) {
 			return; // Ignore files which can't be read as text
 		}
 	}
-
-	private void indexWordForFile(final String word, final String file) {
-		synchronized (this.lock) {
-			this.index.indexWordInFile(word, file);
-		}
-	}
 }

src/main/java/in/ntsh/FileSearchEngine/InvertedIndex.java

@@ -8,6 +8,7 @@
 public class InvertedIndex {
 
 	private final Map<String, Map<String, Integer>> index;
+	private final Object lock = new Object();
 
 	public InvertedIndex() {
 		this.index = new HashMap<String, Map<String, Integer>>();
@@ -20,35 +21,39 @@ public InvertedIndex() {
 	 * @param file
 	 */
 	public void indexWordInFile(final String word, final String file) {
-		// Get Existing index for the word or create a new list
-		Map<String, Integer> fileMap = this.index.get(word);
-		if (fileMap == null) {
-			fileMap = new HashMap<String, Integer>();
-			fileMap.put(file, 1);
-		} else {
-			// Add file and count to index of the word
-			Integer countOfWords = fileMap.get(file);
-			if (countOfWords == null) {
-				countOfWords = 0;
+		synchronized(lock) {
+			// Get Existing index for the word or create a new list
+			Map<String, Integer> fileMap = this.index.get(word);
+			if (fileMap == null) {
+				fileMap = new HashMap<String, Integer>();
+				fileMap.put(file, 1);
+			} else {
+				// Add file and count to index of the word
+				Integer countOfWords = fileMap.get(file);
+				if (countOfWords == null) {
+					countOfWords = 0;
+				}
+				fileMap.put(file, countOfWords + 1);
 			}
-			fileMap.put(file, countOfWords + 1);
+			// Put back word's index to Directory's index
+			this.index.put(word, fileMap);
 		}
-		// Put back word's index to Directory's index
-		this.index.put(word, fileMap);
 	}
 
 	/**
 	 * Returns the List of postings for a given word from the index
 	 * @param word
 	 */
 	public List<Posting> getPostingsForWord(final String word) {
-		final Map<String, Integer> fileMap = this.index.get(word);
+		synchronized(lock) {
+			final Map<String, Integer> fileMap = this.index.get(word);
 
-		final List<Posting> postings = new ArrayList<Posting>();
-		if(fileMap != null) {
-			fileMap.forEach((file, frequency) -> postings.add(new Posting(file, frequency)));
-		}
+			final List<Posting> postings = new ArrayList<Posting>();
+			if(fileMap != null) {
+				fileMap.forEach((file, frequency) -> postings.add(new Posting(file, frequency)));
+			}
 
-		return postings;
+			return postings;
+		}
 	}
 }