Demonstration of the Hashtable class, and an Enumeration

[Java Tip]

Code:

import java.util.Enumeration;
import java.util.Hashtable;

/**
 * Demonstrate the Hashtable class, and an Enumeration.
 * 
 * @see HashMapDemo, for the newer HashMap class.
 */
public class HashtableDemo {

  public static void main(String[] argv) {

    // Construct and load the hash. This simulates loading a
    // database or reading from a file, or wherever the data is.

    Hashtable h = new Hashtable();

    // The hash maps from company name to address.
    // In real life this might map to an Address object...
    h.put("Adobe", "Mountain View, CA");
    h.put("IBM", "White Plains, NY");
    h.put("Learning Tree", "Los Angeles, CA");
    h.put("Microsoft", "Redmond, WA");
    h.put("Netscape", "Mountain View, CA");
    h.put("O'Reilly", "Sebastopol, CA");
    h.put("Sun", "Mountain View, CA");

    // Two versions of the "retrieval" phase.
    // Version 1: get one pair's value given its key
    // (presumably the key would really come from user input):
    String queryString = "O'Reilly";
    System.out.println("You asked about " + queryString + ".");
    String resultString = (String) h.get(queryString);
    System.out.println("They are located in: " + resultString);
    System.out.println();

    // Version 2: get ALL the keys and pairs
    // (maybe to print a report, or to save to disk)
    Enumeration k = h.keys();
    while (k.hasMoreElements()) {
      String key = (String) k.nextElement();
      System.out.println("Key " + key + "; Value " + (String) h.get(key));
    }
  }
}