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Code:



 

package tuning.cache;



import java.util.HashMap;

import java.util.Hashtable;

import java.lang.Math;



public class CacheTest

{

  static Object[] cache_keys = new Object[128];

  static Object[] cache_values = new Object[128];

  static Hashtable hash = new Hashtable();



  public static void main(String[] args)

  {

    try

    {

      System.out.println("started populating");

      populate();

      System.out.println("started accessing");

      access_test();

      access_test();

    }

    catch(Exception e){e.printStackTrace();}

  }



  public static void populate()

  {

    for (int i = 0; i < 100000; i++)

      hash.put(new Integer(i), new Integer(i+5));

  }



  public static Object plain_access(Integer i)

  {

    return hash.get(i);

  }



  public static Object cached_access(Integer i)

  {

    int access = Math.abs(i.hashCode()) & 127;

    Object o;

    if ( (o = cache_keys[access]) == null || !o.equals(i))

    {

      if (o != null)

        System.out.println("Collsion between " + o + " and " + i);

      o = hash.get(i);

      cache_keys[access] = i;

      cache_values[access] = o;

      return o;

    }

    else

    {

      return cache_values[access];

    }

  }



  public static void access_test()

  {

    Integer a0 = new Integer(6767676);

    Integer a1 = new Integer(33);

    Integer a2 = new Integer(998);

    Integer a3 = new Integer(3333);

    Integer a4 = new Integer(12348765);

    Integer a5 = new Integer(9999);

    Integer a6 = new Integer(66665);

    Integer a7 = new Integer(1234);

    Integer a8 = new Integer(987654);

    Integer a9 = new Integer(3121219);

    Object o1,o2,o3,o4,o5,o6,o7,o8,o9,o0;

    long time = System.currentTimeMillis();

    for (int i = 0; i < 1000000; i++)

    {

       o1 = plain_access(a0);

       o2 = plain_access(a1);

       o3 = plain_access(a2);

       o4 = plain_access(a3);

       o5 = plain_access(a4);

       o6 = plain_access(a5);

       o7 = plain_access(a6);

       o8 = plain_access(a7);

       o9 = plain_access(a8);

       o0 = plain_access(a9);

    }

    System.out.println("plain access took " + (System.currentTimeMillis()-time));



    time = System.currentTimeMillis();

    for (int i = 0; i < 1000000; i++)

    {

       o1 = cached_access(a0);

       o2 = cached_access(a1);

       o3 = cached_access(a2);

       o4 = cached_access(a3);

       o5 = cached_access(a4);

       o6 = cached_access(a5);

       o7 = cached_access(a6);

       o8 = cached_access(a7);

       o9 = cached_access(a8);

       o0 = cached_access(a9);

    }

    System.out.println("cached access took " + (System.currentTimeMillis()-time));



  }



}











/*   Java Performance Tuning

 *   Tips and Tools for Killer GUIs

 * By Jack Shirazi

 *   Second Edition January 2003

 *   ISBN: 0-596-00377-3

 *   http://www.oreilly.com/catalog/javapt2/

 */