JAva行単位で超大ファイルを読み込む

以前は超大jsonファイルを読み取るパッケージを書いていましたが、行ごとにファイルを読み取る必要がある場合があります.ここでは行ごとに超大ファイルを読み取るパッケージを提供しています.大jsonファイルを読むには転送ゲートをクリックしてください.
コードに詳細なコメントが書かれていますここでは詳細については説明しません直接コード(コードは参考にしてください)https://www.cnblogs.com/metoy/p/4470418.html,コードに若干の変更がある)

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.io.UnsupportedEncodingException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel.MapMode;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.atomic.AtomicLong;

public class BigFileReader {
    private int threadSize;
    private String charset;
    private int bufferSize;
    private IHandle handle;
    private ExecutorService executorService;
    private long fileLength;
    private RandomAccessFile rAccessFile;
    private Set startEndPairs;
    private CyclicBarrier cyclicBarrier;
    private AtomicLong counter = new AtomicLong(0);

    private BigFileReader(File file, IHandle handle, String charset, int bufferSize, int threadSize) {
        this.fileLength = file.length();
        this.handle = handle;
        this.charset = charset;
        this.bufferSize = bufferSize;
        this.threadSize = threadSize;
        try {
            this.rAccessFile = new RandomAccessFile(file, "r");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        this.executorService = Executors.newFixedThreadPool(threadSize);
        this.startEndPairs = new HashSet();
    }

    /**
     *       
     */
    public void start() {
        long everySize = this.fileLength / this.threadSize;
        try {
            //     
            calculateStartEnd(0, everySize);
        } catch (IOException e) {
            e.printStackTrace();
            return;
        }

        final long startTime = System.currentTimeMillis();
        cyclicBarrier = new CyclicBarrier(startEndPairs.size(), new Runnable() {
            @Override
            public void run() {
                System.out.println("use time: " + (System.currentTimeMillis() - startTime));
                System.out.println("all line: " + counter.get());
                shutdown();
            }
        });

        for (StartEndPair pair : startEndPairs) {
            System.out.println("    ：" + pair);
            this.executorService.execute(new SliceReaderTask(pair));
        }
    }


    /**
     *       
     *
     * @param start
     * @param size
     * @throws IOException
     */
    private void calculateStartEnd(long start, long size) throws IOException {
        if (start > fileLength - 1) {
            return;
        }
        StartEndPair pair = new StartEndPair();
        pair.start = start;
        long endPosition = start + size - 1;
        //       
        if (endPosition >= fileLength - 1) {
            pair.end = fileLength - 1;
            startEndPairs.add(pair);
            return;
        }
        //            ，              
        rAccessFile.seek(endPosition);
        /**
         *                    
         *                
         */
        byte tmp = (byte) rAccessFile.read();
        while (tmp != '
' && tmp != '\r') {
            endPosition++;
            if (endPosition >= fileLength - 1) {
                endPosition = fileLength - 1;
                break;
            }
            rAccessFile.seek(endPosition);
            tmp = (byte) rAccessFile.read();
        }
        pair.end = endPosition;
        startEndPairs.add(pair);
        //     
        calculateStartEnd(endPosition + 1, size);
    }

    private void shutdown() {
        try {
            this.rAccessFile.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
        this.executorService.shutdown();
    }

    /**
     *                   
     * @param bytes
     * @throws UnsupportedEncodingException
     */
    private void handle(byte[] bytes) throws UnsupportedEncodingException {
        String line = null;
        if (this.charset == null) {
            line = new String(bytes);
        } else {
            line = new String(bytes, charset);
        }
        if (line != null && !"".equals(line)) {
            this.handle.handle(line);
            counter.incrementAndGet();
        }
    }

    /**
     *        
     */
    private static class StartEndPair {
        //        
        public long start;
        //        
        public long end;

        @Override
        public String toString() {
            return "star=" + start + ";end=" + end;
        }

        @Override
        public int hashCode() {
            final int prime = 31;
            int result = 1;
            result = prime * result + (int) (end ^ (end >>> 32));
            result = prime * result + (int) (start ^ (start >>> 32));
            return result;
        }

        /**
         *          
         *
         * @param obj
         * @return
         */
        @Override
        public boolean equals(Object obj) {
            if (this == obj)
                return true;
            if (obj == null)
                return false;
            if (getClass() != obj.getClass())
                return false;
            StartEndPair other = (StartEndPair) obj;
            if (end != other.end)
                return false;
            if (start != other.start)
                return false;
            return true;
        }
    }


    /**
     *             
     */
    private class SliceReaderTask implements Runnable {
        private long start;
        private long sliceSize;
        private byte[] readBuff;

        public SliceReaderTask(StartEndPair pair) {
            this.start = pair.start;
            this.sliceSize = pair.end - pair.start + 1;
            this.readBuff = new byte[bufferSize];
        }

        @Override
        public void run() {
            try {
                MappedByteBuffer mapBuffer = rAccessFile.getChannel().map(MapMode.READ_ONLY, start, this.sliceSize);
                ByteArrayOutputStream bos = new ByteArrayOutputStream();
                for (int offset = 0; offset < sliceSize; offset += bufferSize) {
                    int readLength;
                    if (offset + bufferSize <= sliceSize) {
                        readLength = bufferSize;
                    } else {
                        readLength = (int) (sliceSize - offset);
                    }
                    mapBuffer.get(readBuff, 0, readLength);
                    for (int i = 0; i < readLength; i++) {
                        byte tmp = readBuff[i];
                        if (tmp == '
' || tmp == '\r') {
                            handle(bos.toByteArray());
                            bos.reset();
                        } else {
                            bos.write(tmp);
                        }
                    }
                }
                if (bos.size() > 0) {
                    handle(bos.toByteArray());
                }
                cyclicBarrier.await();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

    }

    /**
     *    BigFileReader 
     */
    public static class Builder {
        private int threadSize = 1;
        private String charset = null;
        private int bufferSize = 1024 * 1024;
        private IHandle handle;
        private File file;

        public Builder(String file, IHandle handle) {
            this.file = new File(file);
            if (!this.file.exists())
                throw new IllegalArgumentException("     ！");
            this.handle = handle;
        }

        public Builder withTreahdSize(int size) {
            this.threadSize = size;
            return this;
        }

        public Builder withCharset(String charset) {
            this.charset = charset;
            return this;
        }

        public Builder withBufferSize(int bufferSize) {
            this.bufferSize = bufferSize;
            return this;
        }

        public BigFileReader build() {
            return new BigFileReader(this.file, this.handle, this.charset, this.bufferSize, this.threadSize);
        }
    }


}

/**
 *                
 */
public interface IHandle {

	public void handle(String line);
}

テストコード:

	public static void main(String[] args) {
		BigFileReader.Builder builder = new BigFileReader.Builder("d:/bigFile.txt",new IHandle() {
			@Override
			public void handle(String line) {
				System.out.println(line);
			}
		});
		builder.withTreahdSize(10)
			   .withCharset("gbk")
			   .withBufferSize(1024*1024);
		BigFileReader bigFileReader = builder.build();
                //          
		bigFileReader.start();
	}