import java.util.Map; import java.util.HashMap; import java.util.Iterator; /** * Demonstrate the HashMap class, and an Iterator. * * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002. All rights * reserved. Software written by Ian F. Darwin and others. $Id: LICENSE,v 1.8 * 2004/02/09 03:33:38 ian Exp $ */ public class HashMapDemo { 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. Map map = new HashMap(); // The hash maps from company name to address. // In real life this might map to an Address object... map.put("Adobe", "Mountain View, CA"); map.put("IBM", "White Plains, NY"); map.put("Learning Tree", "Los Angeles, CA"); map.put("Microsoft", "Redmond, WA"); map.put("Netscape", "Mountain View, CA"); map.put("O'Reilly", "Sebastopol, CA"); map.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 = map.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) Iterator k = map.keySet().iterator(); while (k.hasNext()) { String key = k.next(); System.out.println("Key " + key + "; Value " + map.get(key)); } } }