Java-按块读取文本文件

在开始处理块之前，您可以在文件中找到行边界处的偏移量。从偏移量开始，将文件大小除以块号，然后查找直到找到行边界。然后将这些偏移量输入到多线程文件处理器中。这是一个完整的示例，将可用处理器的数量用作块的数量：

import java.io.File;import java.io.IOException;import java.io.RandomAccessFile;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;public class ReadFileByChunks {    public static void main(String[] args) throws IOException {        int chunks = Runtime.getRuntime().availableProcessors();        long[] offsets = new long[chunks];        File file = new File("your.file");        // determine line boundaries for number of chunks        RandomAccessFile raf = new RandomAccessFile(file, "r");        for (int i = 1; i < chunks; i++) { raf.seek(i * file.length() / chunks); while (true) {     int read = raf.read();     if (read == 'n' || read == -1) {         break;     } } offsets[i] = raf.getFilePointer();        }        raf.close();        // process each chunk using a thread for each one        ExecutorService service = Executors.newFixedThreadPool(chunks);        for (int i = 0; i < chunks; i++) { long start = offsets[i]; long end = i < chunks - 1 ? offsets[i + 1] : file.length(); service.execute(new FileProcessor(file, start, end));        }        service.shutdown();    }    static class FileProcessor implements Runnable {        private final File file;        private final long start;        private final long end;        public FileProcessor(File file, long start, long end) { this.file = file; this.start = start; this.end = end;        }        public void run() { try {     RandomAccessFile raf = new RandomAccessFile(file, "r");     raf.seek(start);     while (raf.getFilePointer() < end) {         String line = raf.readLine();         if (line == null) {  continue;         }         // do what you need per line here         System.out.println(line);     }     raf.close(); } catch (IOException e) {     // deal with exception }        }    }}