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多线程处理大文本查找字符串出现的次数

news 来源：原创 2024/9/17 3:54:34

@Service
public class LoadFileStringNum {private static final String FILE_PATH = "C:/Users/36995/Desktop/file.txt";private static final String SEARCH_STRING = "123";public static void main(String[] args) {// 设置线程池大小int numThreads = Runtime.getRuntime().availableProcessors();ExecutorService executor = Executors.newFixedThreadPool(numThreads);List<Future<Long>> futures = new ArrayList<>();long total = 0;try (BufferedReader reader = new BufferedReader(new FileReader(FILE_PATH))) {// 获取文件总行数，用于计算每个线程负责的行数long totalLines = reader.lines().count();// 计算每个线程负责的行数long linesPerThread = totalLines / numThreads;// 提交任务给线程池long startLine = 0;for (int i = 0; i < numThreads; i++) {long endLine = startLine + linesPerThread;if (i == numThreads - 1) {// 最后一个线程处理剩余的行数endLine = totalLines;}futures.add(executor.submit(new SearchTask(FILE_PATH, SEARCH_STRING, startLine, endLine)));startLine = endLine;}// 等待所有任务完成for (Future<Long> future : futures) {total += future.get();}System.out.println("总数: " + total);} catch (Exception e) {System.out.println(e.getMessage());} finally {executor.shutdown();}}
}

public class SearchTask implements Callable<Long> {private final String filePath;private final String searchWord;private final long startLine;private final long endLine;public SearchTask(String filePath, String searchWord, long startLine, long endLine) {this.filePath = filePath;this.searchWord = searchWord;this.startLine = startLine;this.endLine = endLine;}@Overridepublic Long call() throws Exception {long sum = 0;try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {// 跳过前面的行数for (long i = 0; i < startLine; i++) {reader.readLine();}// 查找关键词String line;long lineNumber = startLine + 1;while ((line = reader.readLine()) != null && lineNumber <= endLine) {int index = line.indexOf(searchWord);while (index != -1) {sum++;index = line.indexOf(searchWord, index + 1);}lineNumber++;}}return sum;}
}