归并排序

package my.sort;import java.io.BufferedInputStream;import java.io.BufferedOutputStream;import java.io.BufferedWriter;import java.io.DataInputStream;import java.io.DataOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;import java.io.FileWriter;import java.io.IOException;import java.util.ArrayList;import java.util.Arrays;import java.util.Iterator;import java.util.Random;/** * 基于大数据量的外排序算法，分为二路归并和多路归并 * @author java2king * @link http://blog.csdn.net/Java2King * */public class ExternalSort {public static int ITEM_COUNT = 10000000; //总数     public static int BUFFER_SIZE = 1024*4*1000;// 一次缓冲读取        public static int FILE_COUNT = 1024*1000*1*4;// 每个文件的记录数1        public static File MAIN_FILE = new File("mainset");//要排序的文件    /**     * 二路归并     * @param file     * @return     * @throws IOException     */    public File sort(File file) throws IOException {        ArrayList<File> files = split(file);        return process(files);    }    /**     * 多路归并     * @param file     * @throws IOException     */    public void mSort(File file) throws IOException{    ArrayList<File> files = split(file);    multipleMerge(files);        }    // recursive method to merge the lists until we are left with a    // single merged list    private File process(ArrayList<File> list) throws IOException {        if (list.size() == 1) {            return list.get(0);        }        ArrayList<File> inter = new ArrayList<File>();        for (Iterator<File> itr = list.iterator(); itr.hasNext();) {            File one = itr.next();            if (itr.hasNext()) {                File two = itr.next();                inter.add(merge(one, two));            } else {              //  return one;            inter.add(one);            }        }        return process(inter);    }    /**     * Splits the original file into a number of sub files.      */    private ArrayList<File> split(File file) throws IOException {        ArrayList<File> files = new ArrayList<File>();        int[] buffer = new int[FILE_COUNT];        FileInputStream fr = new FileInputStream(file);        BufferedInputStream bin = new BufferedInputStream(fr,BUFFER_SIZE);        DataInputStream din=new DataInputStream(bin);          boolean fileComplete = false;                while (!fileComplete) {            int index = buffer.length;            for (int i = 0; i < buffer.length && !fileComplete; i++) {            try {             buffer[i] = din.readInt();} catch (Exception e) {fileComplete = true;                    index = i;}            }            if (index != 0 && buffer[0] > -1) {                Arrays.sort(buffer, 0, index);                File f = new File("set" + new Random().nextInt());         //       File temp = File.createTempFile("josp", ".tmp", f);                   FileOutputStream writer = new FileOutputStream(f);                BufferedOutputStream bOutputStream = new BufferedOutputStream(writer);                             DataOutputStream dout=new DataOutputStream(bOutputStream);                 for (int j = 0; j < index; j++) {                    dout.writeInt(buffer[j]);                }                dout.close();                bOutputStream.close();                writer.close();                files.add(f);                           }        }        din.close();        bin.close();        fr.close();        return files;    }    /**     * 多路归并     * @param list     * @throws IOException     */private void multipleMerge(ArrayList<File> list) throws IOException {int fileSize = list.size();if(fileSize == 1){return;}ArrayList<DataInputStream> dinlist = new ArrayList<DataInputStream>();int[] ext = new int[fileSize];//比较数组//File output = new File("multipleMerged");FileOutputStream os = new FileOutputStream(MAIN_FILE);BufferedOutputStream bout = new BufferedOutputStream(os);DataOutputStream dout = new DataOutputStream(bout);for (int i = 0; i < fileSize; i++) {try {dinlist.add(i, new DataInputStream(new BufferedInputStream(new FileInputStream(list.get(i)), BUFFER_SIZE)));} catch (Exception e) {e.printStackTrace();}}int index = 0;for (int i = 0; i < fileSize; i++) {try {ext[i] = dinlist.get(i).readInt();} catch (Exception e) {System.err.println("file_" + i + "为空");ext[i] = -1;}}int count = fileSize;int[] sum = new int[fileSize];while (count > 1) {index = getMinIndex(ext);dout.writeInt(ext[index]);sum[index]++;try {ext[index] = dinlist.get(index).readInt();} catch (Exception e) {ext[index] = -1;count--;dinlist.get(index).close();//System.err.println(index + "空,写进:" +sum[index]);}}int sIndex = getSIndex(ext);dout.writeInt(ext[sIndex]);while (true) {try {dout.writeInt(dinlist.get(sIndex).readInt());} catch (Exception e) {dinlist.get(sIndex).close();break;}}dout.close();}    //找到剩下的最后一个文件输入流    public int getSIndex(int[] ext){    int result = 0;    for (int i = 0; i < ext.length; i++) {if(ext[i]!= -1){result = i;break;}}    return result;    }    //找到数据中最小的一个    public int getMinIndex(int[] ext){    int min = 2147483647;    int index = -1;    for (int i = 0; i < ext.length; i++) {if(ext[i] != -1 && ext[i] < min){min = ext[i];index = i;}}    return index;    }    /**     * 二路归并     *      * @param one     * @param two     * @return     * @throws IOException     */    private File merge(File one, File two) throws IOException {        FileInputStream fis1 = new FileInputStream(one);        FileInputStream fis2 = new FileInputStream(two);        BufferedInputStream bin1 = new BufferedInputStream(fis1,BUFFER_SIZE);        BufferedInputStream bin2 = new BufferedInputStream(fis2,BUFFER_SIZE);                DataInputStream din1=new DataInputStream(bin1);          DataInputStream din2=new DataInputStream(bin2);                  File output = new File("merged" + new Random().nextInt());        FileOutputStream os = new FileOutputStream(output);        BufferedOutputStream bout = new BufferedOutputStream(os);        DataOutputStream dout=new DataOutputStream(bout);            int a = -1;//= din1.readInt();        int b = -1;//= din2.readInt();        boolean finished = false;        boolean emptyA = false;//        int flag = 0;while (!finished) {if (flag != 1) {try {a = din1.readInt();} catch (Exception e) {emptyA = true;break;}}if (flag != 2) {try {b = din2.readInt();} catch (Exception e) {emptyA = false;break;}}if(a > b){dout.writeInt(b);flag = 1;}else if( a < b){dout.writeInt(a);flag = 2;}else if(a == b){dout.write(a);dout.write(b);flag = 0;}}finished = false;if(emptyA){dout.writeInt(b);while(!finished){try {b = din2.readInt();} catch (Exception e) {break;}dout.writeInt(b);}}else{dout.writeInt(a);while(!finished){try {a = din1.readInt();} catch (Exception e) {break;}dout.writeInt(a);}}dout.close();        os.close();    bin1.close();    bin2.close();    bout.close();        return output;    }       /**     * @param args     * @throws IOException     */    public static void main(String[] args) throws IOException {                      Random random = new Random(System.currentTimeMillis());        FileOutputStream fw = new FileOutputStream(MAIN_FILE);        BufferedOutputStream bout = new BufferedOutputStream(fw);        DataOutputStream dout=new DataOutputStream(bout);                  for (int i = 0; i < ITEM_COUNT; i++) {            int ger = random.nextInt();            ger = ger < 0 ? -ger : ger;            dout.writeInt(ger);        }        dout.close();        bout.close();        fw.close();        ExternalSort sort = new ExternalSort();        System.out.println("Original:");        long start = System.currentTimeMillis();        sort.mSort(MAIN_FILE);                       long end = System.currentTimeMillis();        System.out.println((end - start)/1000 + "s");        recordFile((end - start)/1000 ,true);    }    private static void recordFile(long time,boolean isBuffer)            throws FileNotFoundException, IOException {    BufferedWriter bw = new BufferedWriter(new FileWriter("log",true));    bw.write("FILE_COUNT = "+FILE_COUNT+";对"+ ITEM_COUNT + "条数据 "+ ITEM_COUNT*4/(1024*1204) +"MB排序耗时:" + time + "s ");    if(isBuffer){    bw.write("  使用缓冲:"+BUFFER_SIZE*4/(1024*1204) +"MB");    }    bw.newLine();    bw.close();    }}