小内存大数据排序

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.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Random;
 
/**
 * 
 * run configuration -Xms5m -Xmx5m
 * 
 */
public class BigDataSort {
 
    public final static String SMALL_FILE_PATH = "C://BigData//";
    public final static int BIG_NUM_LINE = 200;
    public final static String ORING_FILE_PATH = "C://BigData//bigData.txt";
    public final static int SMALL_FILE_LINE = 10; //1M for 1 small file
    private File tempFiles[];
 
   
 
    private void createBigsortNums() throws IOException {
        BufferedWriter writer = new BufferedWriter(new FileWriter(ORING_FILE_PATH));
        Random random = new Random();
        for (int i = 0; i < BIG_NUM_LINE; i++) {
            writer.write(String.valueOf(random.nextInt(100000000)));
            if(i!=BIG_NUM_LINE-1)writer.newLine();// 确保最后一行不是回车
        }
        writer.close();
    }
  
    private void beSmallFileAndSort() throws IOException {
        BufferedReader bigDataFile = new BufferedReader(new FileReader(ORING_FILE_PATH));
        List smallLine = null;
        tempFiles = new File[BIG_NUM_LINE / SMALL_FILE_LINE];
        for (int i = 0; i < tempFiles.length; i++) {
            tempFiles[i] = new File(SMALL_FILE_PATH + "sortTempFile" + i + ".txt");
            BufferedWriter smallWtite = new BufferedWriter(new FileWriter(tempFiles[i]));
            smallLine = new ArrayList();
            for (int j = 0; j < SMALL_FILE_LINE; j++)
                smallLine.add(Integer.parseInt(bigDataFile.readLine()));
            Collections.sort(smallLine);
            for(int k=0;k	smallWtite.write(String.valueOf(smallLine.get(k)));
            	if(k!=smallLine.size()-1)smallWtite.newLine();
            }
           /* for (Object num : smallLine.toArray())
                smallWtite.write(num + "\n");*/
            smallWtite.close();
        }
    }
 
    private void unitFileToSort() throws IOException {
        File tempFile = null;
        for(int  i=1;i				Thread.sleep(1500);
//			} catch (InterruptedException e) {
//				// TODO Auto-generated catch block
//				e.printStackTrace();
//			}
        }
        File newFile = new File(SMALL_FILE_PATH+"sortResult.txt");
        if(newFile.exists())newFile.delete();
        tempFile.renameTo(newFile);
    }
    /*   private void unitFileToSort() throws IOException {
        File tempFile = null;
        for(int  i=0;i	   BufferedReader fromRd = new BufferedReader(new FileReader(SMALL_FILE_PATH+"1.txt"));
       BufferedReader toTempRd = new BufferedReader(new FileReader(SMALL_FILE_PATH+"2.txt"));
       File newSortFile = new File(SMALL_FILE_PATH+"testunit.txt");
       BufferedWriter newSortFileWt = new BufferedWriter(new FileWriter(newSortFile));
       int index = Integer.MIN_VALUE;
       int toPoint = Integer.MIN_VALUE;
       index = Integer.parseInt(fromRd.readLine());
       toPoint = Integer.parseInt(toTempRd.readLine());
       while (fromRd.ready()||toTempRd.ready()) {
          
           if (index <= toPoint) {
               newSortFileWt.write(String.valueOf(index));
               newSortFileWt.newLine();
               if(fromRd.ready())index = Integer.parseInt(fromRd.readLine());
               else break;
           } else {
               
                   newSortFileWt.write(String.valueOf(toPoint));
                   newSortFileWt.newLine();
                   if(toTempRd.ready())toPoint = Integer.parseInt(toTempRd.readLine());
                   else break;
           }
          


       }
		System.out.println(index + " " + toPoint);
		if (fromRd.ready() && (!toTempRd.ready())) {
			newSortFileWt.write(String.valueOf(index));
			newSortFileWt.newLine();
			while (fromRd.ready()) {
				newSortFileWt.write(fromRd.readLine());
				if (fromRd.ready())newSortFileWt.newLine();
			}
		}
		else if ((!fromRd.ready()) && toTempRd.ready()) {
			newSortFileWt.write(String.valueOf(toPoint));
			newSortFileWt.newLine();
			while (toTempRd.ready()) {
				newSortFileWt.write(toTempRd.readLine());
				if(toTempRd.ready())newSortFileWt.newLine();
			}
		}
		else if((!fromRd.ready())&&(!toTempRd.ready())){
        	newSortFileWt.write(String.valueOf(index<=toPoint?index:toPoint));
        	newSortFileWt.newLine();
            newSortFileWt.write(String.valueOf(index>toPoint?index:toPoint));
           // newSortFileWt.newLine();
        }
           
       
       newSortFileWt.close();
       fromRd.close();
       toTempRd.close();
       
       BufferedReader newFile=new BufferedReader(new FileReader(SMALL_FILE_PATH+"testunit.txt"));
       while(newFile.ready()){
    	   System.out.println(newFile.readLine());
       }
       newFile.close();
   }
    public static File sortBySmallFile(File fromFile, File toFile, int i) throws IOException {
        BufferedReader fromRd = new BufferedReader(new FileReader(fromFile));
        BufferedReader toTempRd = new BufferedReader(new FileReader(toFile));
        File newSortFile = new File(SMALL_FILE_PATH+i+"unit.txt");
        System.out.println(fromFile.getPath());
        BufferedWriter newSortFileWt = new BufferedWriter(new FileWriter(newSortFile));
        int index =  Integer.parseInt(fromRd.readLine());
        int toPoint =  Integer.parseInt(toTempRd.readLine());
        while (fromRd.ready()||toTempRd.ready()) {
            
            if (index <= toPoint) {
                newSortFileWt.write(String.valueOf(index));
                newSortFileWt.newLine();
                if(fromRd.ready())index = Integer.parseInt(fromRd.readLine());
                else break;
            } else {
                
                    newSortFileWt.write(String.valueOf(toPoint));
                    newSortFileWt.newLine();
                    if(toTempRd.ready())toPoint = Integer.parseInt(toTempRd.readLine());
                    else break;
            }
           


        }
        //处理尾数
    	if (fromRd.ready() && (!toTempRd.ready())) {
			newSortFileWt.write(String.valueOf(index));
			newSortFileWt.newLine();
			while (fromRd.ready()) {
				newSortFileWt.write(fromRd.readLine());
				if (fromRd.ready())newSortFileWt.newLine();//确保文件最后一行不是回车
			}
		}
		else if ((!fromRd.ready()) && toTempRd.ready()) {
			newSortFileWt.write(String.valueOf(toPoint));
			newSortFileWt.newLine();
			while (toTempRd.ready()) {
				newSortFileWt.write(toTempRd.readLine());
				if(toTempRd.ready())newSortFileWt.newLine();
			}
		}
		else if((!fromRd.ready())&&(!toTempRd.ready())){
        	newSortFileWt.write(String.valueOf(index<=toPoint?index:toPoint));
        	newSortFileWt.newLine();
            newSortFileWt.write(String.valueOf(index>toPoint?index:toPoint));
           // newSortFileWt.newLine();
        }
        newSortFileWt.close();
        fromRd.close();
        toTempRd.close();
        toFile.delete();
        return newSortFile;
    }
 
    public static void main(String[] args) throws IOException {
    	BigDataSort bds=new BigDataSort();
    	bds.createBigsortNums();
    	bds.beSmallFileAndSort();
    	bds.unitFileToSort();
      //testSort();
    }
}

sortBySmallFile方法思路很简单，但是代码写得不好，没想出好的来。就是把第一个文件与第二个文件按顺序合并，再把合并后的文件与第三个合并，以此类推。