Java NIO 实现大文本文件拆分

package ccb.huge;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.util.Scanner;

/**
 * Java实现大文本文件拆分
 * https://blog.csdn.net/u013632755/article/details/80467324
 */
public class FileUtils {

    public static void splitFile(String filePath, int fileCount) throws IOException {

        FileInputStream fis = new FileInputStream(filePath);
        FileChannel inputChannel = fis.getChannel();
        final long fileSize = inputChannel.size();

        //平均值
        long average = fileSize / fileCount;
        //缓存块大小，自行调整
        long bufferSize = 200;
        // 申请一个缓存区
        ByteBuffer byteBuffer = ByteBuffer.allocate(Integer.valueOf(bufferSize + ""));
        //子文件开始位置
        long startPosition = 0;
        //子文件结束位置
        long endPosition = average < bufferSize ? 0 : average - bufferSize;

        for (int i = 0; i < fileCount; i++) {
            if (i + 1 != fileCount) {
                // 读取数据
                int read = inputChannel.read(byteBuffer, endPosition);
                readW:
                while (read != -1) {
                    //切换读模式
                    byteBuffer.flip();
                    byte[] array = byteBuffer.array();
                    for (int j = 0; j < array.length; j++) {
                        byte b = array[j];
                        //判断\n\r
                        if (b == 10 || b == 13) {
                            endPosition += j;
                            break readW;
                        }
                    }
                    endPosition += bufferSize;
                    //重置缓存块指针
                    byteBuffer.clear();
                    read = inputChannel.read(byteBuffer, endPosition);
                }
            } else {
                //最后一个文件直接指向文件末尾
                endPosition = fileSize;
            }

            FileOutputStream fos = new FileOutputStream(filePath + (i + 1));
            FileChannel outputChannel = fos.getChannel();
            //通道传输文件数据
            inputChannel.transferTo(startPosition, endPosition - startPosition, outputChannel);
            outputChannel.close();
            fos.close();
            startPosition = endPosition + 1;
            endPosition += average;
        }
        inputChannel.close();
        fis.close();

    }

    public static void main(String[] args) throws Exception {

        // Scanner scanner = new Scanner(System.in);
        // String input = scanner.nextLine();
        // System.out.printf("input=%s", input);

        // 拆分个数
        int fileCount = 3;
        String filePath = "d:/ccb/sixno.txt";
        // String filePath = "d:/ccb/ONL_STLM_JNL_410_20190625.dat";

        long startTime = System.currentTimeMillis();
        splitFile(filePath, fileCount);
        long endTime = System.currentTimeMillis();

        System.out.println("耗费时间： " + (endTime - startTime) + " ms");

        // scanner.nextLine();
    }


}

　　转发自：https://blog.csdn.net/u013632755/article/details/80467324