Java Data Structures

Hash Tables 

 HashMapsAndHashTables.java:

/**
 *
 */
package com.it.gnsmind.datastructures;

import java.util.HashMap;
import java.util.Iterator;

/**
 * @author Metin ZAFER
 *
 */
public class HashMapsAndHashTables {

    /**
     *
     */
    public HashMapsAndHashTables() {

        System.out.println("Hash Map application object has been initialized. ");
    }

    //hashMap and HashTable basicly the same structured objects
    public void hashMapsAndhashTables(){
       
        // Hash maps are used mostly in database applications or web services.
        // This structure is very useful because of the dynamic allocation.
        // We do not have to specify the index number at the beginning of our application like arrays.
        // It gives us very flexible array structure to use in our productive applications.
        HashMap h = new HashMap( );
       
        h.put("key1", "Value1");
        h.put("key2", "Value2");
        h.put("key3", "Value3");
        h.put("key4", "Value4");
        h.put("key5", "Value5");
       
        // Two versions of the "retrieval" phase.
        // Version 1: get one pair's value given its key
        String queryString = "key1";
        System.out.println("You asked : " + queryString + ".");
        String resultString = (String)h.get(queryString);
        System.out.println("The Value is located in: " + resultString);
        System.out.println( );
       
        // Version 2: get all the keys and pairs
        Iterator it = h.keySet( ).iterator( );
       
        while (it.hasNext( )) {
           
            String key = (String) it.next( );
            System.out.println("The Hash Map Key : " + key + "; " + "- Value : " + h.get(key));
        }
    }
   
   
}

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