Java: VD về Hastable

1. Tim trong tu dien
import java.util.*;

public class HashTableExample {
    public static void main(String args[]) {
        Hashtable tdav = new Hashtable();
        tdav.put("Hello","Chao");
        tdav.put("Begin","Bat dau");
        tdav.put("End","Ket thuc");

        //Tim tu trong tu dien
        String tu = "Begin";
        if (tdav.containsKey(tu))
            System.out.println(tu+" : "+tdav.get(tu));
        else
            System.out.println("Khong co tu:"+tu);
    }
}

2. Dem so tu trung nhau
import java.util.Enumeration;
import java.util.Hashtable;
import java.util.StringTokenizer;

public class countWords {
    public static void main(String[] args) {
        Hashtable h = new Hashtable();
        String s = "to be or not to be";
        StringTokenizer st = new StringTokenizer(s," ");
        //System.out.println("So tu:"+st.countTokens());

        while (st.hasMoreTokens()) {
            //System.out.println(st.nextToken());
            String ns = st.nextToken();
            if(h.containsKey(ns))
            {
                int i = (int)h.get(ns);
                h.put(ns, ++i);
                //System.out.println(ns + " " + i);
            }
            else{
                h.put(ns, 1);
                //System.out.println(ns + " =1");
            }
        }

        Enumeration e2 = h.elements();
        Enumeration e1 = h.keys();

        while (e1.hasMoreElements())
            System.out.println(e1.nextElement().toString() + " " + e2.nextElement().toString());
    }
}