算法的Java实现

引用:
http://www.java3z.com/cwbwebhome/article/article5/51296.html?id=3438 

public class  SimpleBloomFilter {
    private static final  int  DEFAULT_SIZE  = 14 ;
    private static final  int [] seeds =new  int []{5};
    private  BitSet bits= new  BitSet(DEFAULT_SIZE);
    private  SimpleHash[]  func = new  SimpleHash[seeds.length];
    
    public static void  main(String[] args) {
       String value  = "[e-mail]" ;
       SimpleBloomFilter filter = new  SimpleBloomFilter();
       System.out.println(filter.contains(value));
       filter.add(value);
       System.out.println(filter.contains(value));
   }
    
   public  SimpleBloomFilter() {
        for( int  i= 0 ; i< seeds.length; i ++ ) {
           func[i] = new  SimpleHash(DEFAULT_SIZE, seeds[i]);
       }
   }
   
   
   public void  add(String value) {
        for(SimpleHash f : func) {
           bits.set(f.hash(value),true);
       }
   }
    public boolean  contains(String value) {
        if(value ==null ) {
            return false ;
       }
        boolean  ret  = true ;
        for(SimpleHash f : func) {
           ret=ret&& bits.get(f.hash(value));
        }
        return  ret;
   }
    
    
    public static class SimpleHash {
        private int  cap;
        private int  seed;
        public  SimpleHash( int cap, int seed) {
            this.cap= cap;
            this.seed =seed;
       }
        public int hash(String value) {
            int  result=0 ;
            int  len= value.length();
            for  (int i= 0 ; i< len; i ++ ) {
               result =seed* result + value.charAt(i);
           }
            return (cap - 1 ) & result;
       }
   }
    
    
    
}