上圖(畫的圖真難看，不知道什麼工具比較好?)是使用三個雜湊函式的Bloom Filter中添加了幾個物件(x,y,z)的過程。無論以前的狀態是什麼，位元位都被設定為1，在位陣列中的1的個數只能增加。物件(如x,y,z)被確定地雜湊到陣列中的位上，而這些位被設定為1，通過雜湊並檢查那些位置上的位元值，可以檢視一個物件是否在這個集合中。

package cn.zhf.test;
import java.io.BufferedReader;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.BitSet;
import java.util.HashMap;
import java.util.Map;
import java.util.Random;
public class BloomFilter<E> {
 private BitSet bs;
 private int bitArraySize = 100000000;
 private int numHashFunc = 6;
 public BloomFilter(){
  bs = new BitSet(bitArraySize);
 }
 
 public void add(E obj){
  int[] indexes = getHashIndexes(obj);
  for(int index : indexes)
   bs.set(index);
 }
 
 public boolean contains(E obj){
  int[] indexes = getHashIndexes(obj);
  for(int index : indexes)
   if(bs.get(index) == false)
    return false;
  return true;
 }
 
 public void union(BloomFilter<E> other){
  bs.or(other.bs);
 }
  /*粗略實現，採用MD5雜湊作為java隨機數生成器的種子並取k個隨機數作為索引*/
 public int[] getHashIndexes(E obj){
  int[] indexes = new int[numHashFunc];
  long seed = 0;
  byte[] digest;
  try {
   MessageDigest md = MessageDigest.getInstance("MD5");
   md.update(obj.toString().getBytes());
   digest = md.digest();
   for(int i=0;i<6;i++)
    seed = seed^(((long)(digest[i] & 0xFF)) << (8*i));
  } catch (NoSuchAlgorithmException e) {
   e.printStackTrace();
  }
  Random gen = new Random(seed);
  for(int i=0;i<numHashFunc;i++)
   indexes[i] = gen.nextInt(bitArraySize);
  return indexes;
 }
 
 public void write(DataOutput out) throws IOException{
  int byteArraySize = (int)(bitArraySize / 8);
  byte[] byteArray = new byte[byteArraySize];
  for(int i=0;i<byteArraySize;i++){
   byte nextElement = 0;
   for(int j=0;j<8;j++){
    if(bs.get(8*i+j))
     nextElement |= 1<<j;
   }
   byteArray[i] = nextElement;
  }
  out.write(byteArray);
 }
 
 public void readFileds(DataInput in) throws IOException{
  int byteArraySize = (int)(bitArraySize / 8);
  byte[] byteArray = new byte[byteArraySize];
  in.readFully(byteArray);
  for(int i=0;i<byteArraySize;i++){
   byte nextByte = byteArray[i];
   for(int j=0;j<8;j++){
    if(((int)nextByte & (1<<j)) != 0)
     bs.set(8*i+j);
   }
  }
 }
 public Map<Integer,String> readFile(String filePath){
        BufferedReader br;
        Map<Integer,String> map = new HashMap<Integer,String>();
  try {
   br = new BufferedReader(new InputStreamReader(
           new FileInputStream(filePath)));
   int i = 0;
   for (String line = br.readLine(); line != null; line = br.readLine()) {
             map.put(i++, line);
         }
   br.close();
  } catch (FileNotFoundException e) {
   e.printStackTrace();
  } catch (IOException e) {
   e.printStackTrace();
  }
        return map;
    }
 public static void main(String[] args) {
  BloomFilter<String> bf = new BloomFilter<String>();
  Map<Integer,String> map = bf.readFile("C:\\Users\\zhf\\Desktop\\test.txt");
  for(Map.Entry<Integer, String> m : map.entrySet())
   bf.add(m.getValue());
  boolean flag = bf.contains("15");
  System.out.println(flag);
 }
}