Visit to Niagara Falls - May 23 to 25 2015

Is there a shortcut which invokes the “Login Window…” on MAC ? - NO

I got tired of clicking on "Login Windows..." on my mac when I want to lock my logged user account. I discovered a solution to create a easy shortcut command to solve this problem. If you also want to give it a try, you can :)

• Start Applications » Automator
• Select "Service" for the template of the new Automator workflow
• In the top of the right pane, select "Service receives no input in any application"
• Drag action "Run Shell Script" from the left pane into the workflow on the right pane
• Leave Shell at its default "/bin/bash", and replace the default command cat with the following, without any line breaks:

  /System/Library/CoreServices/Menu\ Extras/User.menu/Contents/Resources/CGSession -suspend

• Optional: click the Run button to test
• Hit Cmd-S to save. The name you type will be the name in the Services menu. The workflow will be saved in ~/Library/Services.

To assign a keyboard shortcut, in 10.6:

• Open System Preferences » Keyboard » pane Keyboard Shortcuts
• Select "Services" in the left pane
• Scroll down to General in the right pane
• Double-click to the right of the Automator workflow you just created
• Press the keys you want to use, and switch panes to ensure the new shortcut is saved.

For details please click here.

Memory Leak

As we know Java is the garbage collected language. Programmer do not need to worry about the memory management. But its not true always.

The memory leak can reduced the performance due to the increased garbage collector activity resulting disk paging and even program failure with an OutOfMemoryError.

Consider the following simple implementation of stack,

import java.util.Arrays;
import java.util.EmptyStackException;

/**
 *
 * @author
 */
public class Stack {

    private Object[] elements;
    private int size = 0;
    private static final int DEFAULT_INITIAL_CAPACITY = 16;

    public Stack() {
        elements = new Object[DEFAULT_INITIAL_CAPACITY];
    }

    public void push(Object e) {
        ensureCapacity();
        elements[size++] = e;
    }

    public Object pop() {
        if (size == 0) {
            throw new EmptyStackException();
        }
        return elements[--size];
    }

    /**
     * Ensure space for at least one more element, roughly doubling the capacity
     * each time the array needs to grow.
     */
    private void ensureCapacity() {
        if (elements.length == size) {
            elements = Arrays.copyOf(elements, 2 * size + 1);
        }
    }
}

Did you spot the memory leak ?

If the stack grows and then shrinks, the objects that were popped off the stack will not be garbage collected, This is because the stack maintain the absolute reference to these objects.

If an object reference is unintentionally retained, not only object excluded from garbage collection, but also many many objects may be prevented from being garbage collected, with potentially large effect on performance.

Solution : null out the reference once they become obsolete.

public Object popCorrected() {
        if (size == 0) {
            throw new EmptyStackException();
        }
        Object result = elements[--size];
        elements[size] = null; // Eliminate obsolete reference
        return result;
    }

whenever a class manages its own memory, the programmer should be alert for memory leaks.

Another common source of memory leaks is caches.

Source: Effective Java 2nd Edition, Chapter 2

Design Pattern : Builder

When we have so many parameters in constructor. To deal with this problem we have an alternative to use the Builder pattern. We define a static inner class Builder, whose job it is to collect the parameters and then construct the object in one fell swoop

Example:

public class NutritionFacts {
private final int servingSize;
private final int servings;
private final int calories;
private final int fat;
private final int sodium;
private final int carbohydrate;
public static class Builder {
      // Required parameters
      private final int servingSize;
      private final int servings;
      // Optional parameters - initialized to default values
      private int calories = 0;
      private int fat = 0;
      private int carbohydrate = 0;
      private int sodium = 0;

      public Builder(int servingSize, int servings) {
         this.servingSize = servingSize;
         this.servings = servings;
      }

      public Builder calories(int val)
         { calories = val; return this; }

      public Builder fat(int val)
         { fat = val; return this; }

      public Builder carbohydrate(int val)
         { carbohydrate = val; return this; }

      public Builder sodium(int val)
         { sodium = val; return this; }

      public NutritionFacts build() {
        return new NutritionFacts(this);
      }
   }

   private NutritionFacts(Builder builder) {
      servingSize = builder.servingSize;
      servings = builder.servings;
      calories = builder.calories;
      fat = builder.fat;
      sodium = builder.sodium;
      carbohydrate = builder.carbohydrate;
   }
}

Note that NutritionFacts is immutable, and that all parameter default values

are in a single location. The builder’s setter methods return the builder itself so

that invocations can be chained. Here’s how the client code looks:

NutritionFacts cocaCola = new NutritionFacts.Builder(240, 8).

calories(100).sodium(35).carbohydrate(27).build();

This client code is easy to write and, more importantly, to read. The Builder pattern

simulates named optional parameters.

In summary, the Builder pattern is a good choice when designing classes

whose constructors or static factories would have more than a handful of

parameters, especially if most of those parameters are optional.

Source : Effective Java 2nd Edition Chapter 2

jQuery Validiate Custome Rules

Followings are the few custom rule to validate German telephone and zip followed by city.

German telephone:

jQuery.validator.addMethod("checkTelephone", function(value, element) {return this.optional(element) || /^([\+][0-9]{1,3}[ \.\-])?([\(]{1}[0-9]{1,6}[\)])?([0-9 \.\-\/] {3,20})    ((x|ext|extension)[ ]?[0-9]{1,4})?$/.test(value);
});

zip followed by city:

jQuery.validator.addMethod("checkPlzort", function(value, element) {return this.optional(element) || /^(?!01000|99999)(0[1-9]\d{3}|[1-9]\d{4})([a-zA-Zäöüß  \s\d()/\-)]+?)$/.test(value);
 });

Replication of local Database to live Database

Recently i was working for one of the Government Office's Intranet based software. I had to develop a module "Sync Database to live". It was only replication (from Localhost to live site).

Mysql has replication feature. As i had little time to implement so i thought understanding of it and implementing into project will take me longer time. Then i developed my own module. Which i m going to describe here.

Firstly i prepared array of tables which are need to be replicated.
 e.g : $tables = array('authors','book_authors','publication','books','book_category');

Using PHPExcel, I generated the  multi-sheet excel file with all the data from given tables in respective sheet dynamically.

Using cURL, I uploaded excel file to target  (live server). Then i had to run a script in live server via cURL which reads the excel file and insert data to respective tables of live database.


        $ch = curl_init();
        $data = array('file' => "@$filepath");
        curl_setopt($ch, CURLOPT_URL, 'http://localhost/upload/upload.php');
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $data);

        curl_exec($ch);

Sending @ before the filepath makes sure that cURL sends the file as a part of a “multipart/form-data” post. That was what i exactly needed.

IDEA that can change the "YOUTH"

 Five points that can change the youth (with the perspective of Information technology):

1)develop a platform, where all youth can participate n can share their problem about making right decision  at  right time, what their family wants from them and importantly what they wants themself in their life.

2)Individual counceling through a radio program. Program that is dedicated to youth, wher there will be lots of discussion concerning about the how youth can be benifited from education  i.e involvement of youth in science and technology....so that they can develop their career in Information and Technology field.

3)personal from IT sector(engineers, software developers, network engineers, professors, system admin) can give a presentation for group of youth or in selected school where they give their presentation on challeenges and future in IT.they can develop  interest of student in IT, motivation is the key factor to attract the student in IT sector.they will explore what is the benifit of IT......in their presentation and youth can be attracted.

4)Concept of E- Library in school. Students can know lots of things about Information technology with the use of computer.Indirectly that will help to change in behavoir of student and enthusiasm to know new thing, innovative idea and eager to know new things will develop. "Learning by doing" ultimately youth can be surely attracted in IT field.

5)Make a group of Youth(every youth are having some sorts of problems,ie what is their intrest and what they exactly wants to become in future). Start a discussion about their problems, they will share individual problems in group and will discuss what could be the solution of problems and ofcourse you can be one facilitator to them.

Conclusion:

Its not necessary for every students ( youth ) to go to science and technology  field but if most of youth are from science and technology background, it  will be easy to develop the nation."Engineers moves the nation ahead". More the engineers, fast will be the development of nation. For this all, there should be political stability and proper policies to utilise educated manpower and technomanagerial personals with in the country.