Algorithm 6-5: a set of hash table applications

You can use a hash table to perform efficient set operations.

Interface

A collection object can contain the following interfaces:

public interface Set
 
  > {    public void add(Key key);    public boolean contains(Key key);    public void remove(Key key);    public int size();    public Iterator
  
    iterator();}
  
 

Blacklist Filtering Application

Code

Import java. util. set; import java. util. linkedHashSet; public class BlackList {public static void main (String [] argv) {String [] urls = new String [] {"baidu.com", "abc.com", "porn.com ", "youtube.com", "facebook.com"}; String [] blacklist = new String [] {"porn.com", "youtube.com", "facebook.com"}; // create a blacklist Set
 
  
Black = new LinkedHashSet
  
   
(); For (String B: blacklist) {black. add (B);} // filter illegal websites for (String url: urls) {if (! Black. contains (url) {System. out. println (url );}}}}
  
 

Output result:

baidu.comabc.comporn.com is blockedyoutube.com is blockedfacebook.com is blocked

The output results show that some illegal websites are filtered out.