/**
 * Java Collections Framework > HashMapExample.java
 *
 * Use a HashMap to store objects and retrieve them using keys.  HashMaps
 * are faster than TreeMaps at retrieval but do not store their elements in 
 * sorted order. 
 * @author  Feihong Hsu
 */

import java.util.Map;           // Superclass of HashMap
import java.util.HashMap;       // A container that supports quick retrieval
import java.util.Iterator;      // Used to traverse the HashMap

public class HashMapExample {
    
    // This method prints all the mappings in the given HashMap object.
    public static void printHashMap(HashMap hashMap) {
        System.out.print( "HashMap: " );
        
        // Use an Iterator to traverse the mappings in the TreeMap.
        Iterator iterator = hashMap.entrySet().iterator();
        
        while (iterator.hasNext()) {
            Map.Entry entry = (Map.Entry) iterator.next();
            System.out.print( "(" + entry.getKey() + ": " + 
                              entry.getValue() + "), " );
        }
        System.out.println();
    }
    
    public static void main(String[] args) {
        HashMap hashMap = new HashMap();
        
        // Put 4 mappings into the HashMap.
        hashMap.put("Pharaoh", new Integer(55));
        hashMap.put("Emperor", new Double(2.33));
        hashMap.put("Kaiser", new Long(323322L));
        hashMap.put("Czar", new Boolean(true));
        
        // "HashMap: (Pharaoh: 55), (Czar: true), (Kaiser: 323322), 
        // (Emperor: 2.33), "
        printHashMap(hashMap);
        
        // Get the value associate with the key "Emperor"--prints 2.33.
        System.out.println("Value for key Emperor: " + 
                           hashMap.get("Emperor") );
        
        // Remove the hashMapping with key "Kaiser".
        hashMap.remove("Kaiser");
        
        // "HashMap: (Pharaoh: 55), (Czar: true), (Emperor: 2.33), "
        printHashMap(hashMap);
        
        // Find out if the HashMap has the key "Sultan".
        System.out.println( "Has key Sultan? " + 
                            hashMap.containsKey("Sultan") );  // Prints false
    }    
}

/* Output:

HashMap: (Pharaoh: 55), (Czar: true), (Kaiser: 323322), (Emperor: 2.33), 
Value for key Emperor: 2.33
HashMap: (Pharaoh: 55), (Czar: true), (Emperor: 2.33), 
Has key Sultan? false

*/