将一个无法一次读入内存的大文件排序

弄了一整天才弄出来 直接上代码

package com.test;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Random;

/**
 * 
 * @author wangyuyuan
 * 将一个大文件中的数据排序 无法一次读入内存情况的处理方法
 *
 */
public class LargeDataSortTest {
    static File file = new File("E:"+File.separator+"dataTest"+File.separator+"data.txt");
    static File file1 = new File("E:"+File.separator+"dataTest"+File.separator+"dataSorted.txt");
    public static void main(String[] args) throws Exception{
        createData();
        System.out.println("大文件写入成功");
        separateFile();
        System.out.println("文件拆分成功");
    
        everySingleFileSort();
        System.out.println("小文件排序完成");
        mergeFile();
        System.out.println("所有排序都已完成");
        
    }
    public static void createData() throws IOException{
        FileWriter fw = new FileWriter(file);
        BufferedWriter bw = new BufferedWriter(fw);
        Random random = new Random();
        for(int i=0;i<1000000;i++){
            bw.write(random.nextInt(Integer.MAX_VALUE)+"\r\n");
        }
        bw.close();
        fw.close();
    }
    public static void separateFile() throws IOException{
        FileReader fr = new FileReader(file);
        BufferedReader br = new BufferedReader(fr);
        FileWriter fw = null;
        BufferedWriter bw = null;
        List<FileWriter> fwList = new LinkedList<FileWriter>();
        List<BufferedWriter> bwList = new LinkedList<BufferedWriter>();
        for(int i=0;i<20;i++){
            fw = new FileWriter("E:"+File.separator+"dataTest"+File.separator+"data"+i+".txt");
            bw = new BufferedWriter(fw);
            //把对象放入集合
            fwList.add(fw);
            bwList.add(bw);
        }
        
        while(br.ready()){
            for(Iterator<BufferedWriter> iterator=bwList.iterator();iterator.hasNext();){
                BufferedWriter it = iterator.next();
                it.write(br.readLine()+"\r\n");
                continue;//第一个bw读完后让下一个读 然后写入小文件
            }
        }
        br.close();
        fr.close();
        //遍历关闭所有子文件流   
        for (Iterator iterator = bwList.iterator(); iterator.hasNext();) {
            BufferedWriter it = (BufferedWriter) iterator.next();
            it.close();
        }
        
        for (Iterator iterator = fwList.iterator(); iterator.hasNext();) {
            FileWriter it = (FileWriter) iterator.next();
            it.close();
        }
    }
    //对每个小文件进行排序
    public static void everySingleFileSort() throws Exception{
        LinkedList<Integer> numbers ;
        for(int i=0;i<20;i++){
            numbers = new LinkedList<Integer>();
            String path = "E:"+File.separator+"dataTest"+File.separator+"data"+i+".txt";
            FileReader fr = new FileReader(path);
            BufferedReader br = new BufferedReader(fr);
            while(br.ready()){
                numbers.add(Integer.parseInt(br.readLine()));
            }
            Collections.sort(numbers);
            numbersWrite(numbers,path);
            br.close();
            fr.close();
        }
    }
    //将排好序的没个文件写回到小文件中
    public static void numbersWrite(LinkedList<Integer> numbers,String path) throws IOException{
        FileWriter fw  = new FileWriter(path);
        BufferedWriter bw = new BufferedWriter(fw);
        for(Iterator<Integer> iterator=numbers.iterator();iterator.hasNext();){
            Integer num = (Integer)iterator.next();
            bw.write(num+"\r\n");
        }
        bw.close();
        fw.close();
    }
    //再将所有小文件整合到一个大文件中
    public static void mergeFile() throws Exception{
        PriorityQueue<Obj> queue = new PriorityQueue<Obj>(20,new Obj());
        FileReader fr = null;
        BufferedReader br = null;
        FileWriter fw = new FileWriter(file1);
        BufferedWriter bw = new BufferedWriter(fw);
        List<FileReader> frList = new LinkedList<FileReader>();
        List<BufferedReader> brList = new LinkedList<BufferedReader>();
        int n;
        for(int i=0;i<20;i++){
            String path = "E:"+File.separator+"dataTest"+File.separator+"data"+i+".txt";
            fr = new FileReader(path);
            br = new BufferedReader(fr);
            frList.add(fr);
            brList.add(br);
        }
        //把每个小文件的第一个数读入队列中
        for(int i=0;i<=20;i++){
            BufferedReader buffR;
            if(i==20){
                while(queue.size()!=0){
                    Obj obj = queue.poll();
                    bw.write(obj.a+"\r\n");
                    buffR = brList.get(obj.b);
                    while(buffR.ready()&&queue.size()<20){
                        n = Integer.parseInt(buffR.readLine());
                        queue.add(new Obj(n,obj.b));
                    }
                }
                break;
            }
            buffR = brList.get(i);
            while(buffR.ready()&&queue.size()<20){
                n = Integer.parseInt(buffR.readLine());
                Obj obj = new Obj(n,i);
                queue.add(obj);
                break;
            }
        }
        bw.close();
        fw.close();
        //遍历关闭所有子文件流   
        for (Iterator iterator = brList.iterator(); iterator.hasNext();) {
            BufferedReader it = (BufferedReader) iterator.next();
            it.close();
        }
        
        for (Iterator iterator = frList.iterator(); iterator.hasNext();) {
            FileReader it = (FileReader) iterator.next();
            it.close();
        }
    }
}

class Obj implements Comparator<Obj>{
    int a,b;
    Obj(){}
    Obj(int a,int b){
        this.a =a;
        this.b=b;
    }
    public int compare(Obj o1, Obj o2) {
        return o1.a-o2.a;
    }
}