新浪面试题-多线程合并文件

今日我收到了一封来自新浪面试的面试邮件，里面就有一道面试题。就是要求多线程合并一个文件，写我整整两天的时间搞定这个题目，给大家分享一下，看代码。

主程序

package com.huang;import org.apache.log4j.Logger;import java.util.concurrent.*;/** * 主程序，本程序采用生产者消费者模型，对多个文件进行读写操作 * Created by root on 16-9-1. */public class Main {    private static final Logger MAIN_LOGGER=Logger.getLogger(Main.class);    private static final Logger CON_LOGGER=Logger.getLogger(Consumer.class);    private static final Logger PRO_LOGGER=Logger.getLogger(Producer.class);    private static final  ExecutorService POOL;    //使用阻塞队列实现生产者消费者    private static final BlockingQueue BLOCKING_QUEUE = new LinkedBlockingQueue();    static{        //获取CPU核数        int cpuNum=Runtime.getRuntime().availableProcessors();        //因为是IO密集型的程序，如果是CPU密集型程序则N+1        POOL= Executors.newFixedThreadPool(2*cpuNum+1);    }    public static void main(String args[]){        String in[]={"/tmp/a","/tmp/b","/tmp/c"};        String out="/tmp/d";        for(int i=0;i<in.length;i++){            POOL.execute(new Producer(BLOCKING_QUEUE,in[i],PRO_LOGGER));        }        POOL.shutdown();        new Thread(new Consumer(BLOCKING_QUEUE,CON_LOGGER,out,in.length)).start();    }}

生产者

package com.huang;import org.apache.log4j.Logger;import java.io.IOException;import java.util.concurrent.BlockingQueue;/** * 生产者 * Created by root on 16-8-31. */public class Producer implements Runnable{    private BlockingQueue<Byte[]> blockingQueue;    private String filePath;    private Logger logger;    public Producer(BlockingQueue blockingQueue,String filePath,Logger logger) {        this.blockingQueue=blockingQueue;        this.filePath=filePath;        this.logger=logger;    }    @Override    public void run() {        try {            Byte[] data=FileOperate.toArray(FileOperate.getFileByte(filePath));            blockingQueue.add(data);        } catch (IOException e) {            logger.error(e.getMessage(),e);        }    }}

消费者

package com.huang;import org.apache.log4j.Logger;import java.io.IOException;import java.util.concurrent.BlockingQueue;/** *消费者 * Created by root on 16-8-31. */public class Consumer implements Runnable{    private final BlockingQueue<Byte[]> blockingQueue;    private Logger logger;    private String outFile;    private int num;    public Consumer(BlockingQueue blockingQueue,Logger logger,String outFile,int num){        this.blockingQueue=blockingQueue;        this.logger=logger;        this.outFile=outFile;        this.num=num;    }    @Override    public void run() {        while(true){            try {                Byte[] bytes=blockingQueue.take();                FileOperate.writeByte(outFile,bytes);                if(--num==0)                    break;            } catch (InterruptedException e) {                logger.error(e.getMessage(),e);            } catch (IOException e) {                logger.error(e.getMessage(),e);            }        }    }}

文件操作工具类

package com.huang;import java.io.*;import java.nio.ByteBuffer;import java.nio.channels.FileChannel;import java.util.ArrayList;import java.util.List;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;/** * Created by root on 16-8-31. */public class FileOperate {    /**     * 使用NIO对文件进行写操作     * @param filePath     * @param bytes     * @throws IOException     */    public static void  writeByte(String filePath,Byte[] bytes) throws IOException {        Lock lock=new ReentrantLock();        File outFile=new File(filePath);        if(!outFile.exists())            outFile.createNewFile();        try(FileOutputStream fileOutputStream=new FileOutputStream(outFile,true); FileChannel fileChannel=fileOutputStream.getChannel();){            ByteBuffer bf=ByteBuffer.wrap(getBytes(bytes));            fileChannel.write(bf);        }    }    /**     *使用NIO对文件进行读操作     * @param filePath     * @return     * @throws IOException     */    public static List<Byte> getFileByte(String filePath) throws IOException {        File inFile=new File(filePath);        List<Byte> bytes=null;        try (FileInputStream fileInputStream= new FileInputStream(filePath); FileChannel fc=fileInputStream.getChannel();){            bytes=new ArrayList<>();            ByteBuffer bf=ByteBuffer.allocate(1024);            while(fc.read(bf)!=-1) {                bf.flip();                while(bf.hasRemaining())                    bytes.add(bf.get());                bf.clear();            }        } catch (FileNotFoundException e) {            throw new RuntimeException(filePath+"您输入的文件路径有误");        }        return bytes;    }    public static Byte[] toArray(List<Byte> list){        Byte[] result=new Byte[list.size()];        for(int i=0;i<list.size();i++){            result[i]=list.get(i);        }        return result;    }    public static byte[] getBytes(Byte[] bytes){        byte[] result=new byte[bytes.length];        for(int i=0;i<result.length;i++){            result[i]=bytes[i];        }        return result;    }}