位图排序

位图排序： 适合数量较多的整数集合排序。

原理：  定义位组，如果整数i存在，则将位组的第i位置为1，以记录其存在。然后位组遍历，确定排序。

Code: 

　　

import java.io.*;
import java.util.*;
public class Main {
    
    
public static void main(String[] argc) throws IOException{

        Main test = new Main();
        String largeFileName = "d:\File_test\old.txt";
        String destlargeFileName = "d:\File_test\new.txt";
        test.perform(largeFileName, 100, destlargeFileName,true);
}
    

private BitSet bits;
public void perform( String largeFileName,int total, String destLargeFileName,boolean asc) throws IOException {
System.out.println("BitmapSort Started.");
 long start = System.currentTimeMillis();
 bits = new BitSet(total);
 FileWriter fw=new FileWriter(new File(destLargeFileName));
 BufferedWriter  largeOut=new BufferedWriter(fw);
 File fr = new File(largeFileName);
 BufferedReader largeIn = new BufferedReader(new FileReader(fr));
 
// OutputStreamWriter osw=new OutputStreamWriter(fos, "UTF-8");
//BufferedWriter  bw=new BufferedWriter(osw);
 Integer data;
 int off = 0;
 try {
 while (true) {
 String Data = largeIn.readLine();
 if (Data == null)
 break;
 data = Integer.parseInt(Data);
 int v = data;
 set(v);
 off++;
 }
 largeIn.close();
 int size = bits.size();
 System.out.println(String.format("lines : %d ,bits : %d", off, size));
 if(asc) {
     for (int i = 0; i < size; i++) {
     if (get(i)) {
         largeOut.write(String.valueOf(i)+"
");
         largeOut.write("	
");
     }
     }
 }
 largeOut.close();
 long stop = System.currentTimeMillis();
 long elapsed = stop - start;
 System.out.println(String.format("BitmapSort Completed.elapsed : %dms",elapsed));
 }
 finally {
 largeIn.close();
 largeOut.close();
     } 
 }

private void set(int i) {
 bits.set(i);
 }
private boolean get(int v) {
 return bits.get(v);
 }
}