alex-arriaga

alex-arriaga July 16, 2013

How to use and understand Binary Search on Java SE

Enterprise Development, Java EE 2 Replies

Java is a Platform to create robust, secure and scalable stand-alone and enterprise web applications. It has a lot of classes and resources that make easy to develop many functionalities in systems. One of the most interesting parts of the Java API (Application Programming interface) is work with collections and generics. Basically, Java has three kinds of “collections”: Set, List and Map (this one is not necessarily a collection but it is enough alike than one, so its use doesn’t cause any problem, if we understand how collections work).

Well, in Java there is a special static class called Arrays (java.util.Arrays),

This class contains various methods for manipulating arrays (such as sorting and searching). This class also contains a static factory that allows arrays to be viewed as lists.

Today, I would like to show you how to use a method that implements Binary Search, but before we could check the official information about this method:

Binary Search method. Searches the specified array of ints for the specified value using the binary search algorithm. The array must be sorted (as by the sort(int[]) method) prior to making this call. If it is not sorted, the results are undefined. If the array contains multiple elements with the specified value, there is no guarantee which one will be found.

This method has a lot of overrides, for more information about them, please visit: http://docs.oracle.com/javase/6/docs/api/java/util/Arrays.html#binarySearch(java.lang.Object[], java.lang.Object)

Now, imagine that we have the next code:

import java.util.*;

public class ArraysTest{
	public static void main(String [] args) {
		String [] colors = {"blue", "red", "green", "yellow", "orange"};

		// It is necessary to have an ordered array
		Arrays.sort(colors);
		for(String color : colors)
			System.out.print(color + " ");

		int index1 = Arrays.binarySearch(colors, "orange");
		int index2 = Arrays.binarySearch(colors, "violet");
		System.out.println("\norange => " + index1);
		System.out.println("violet => " + index2);
	}
}

import java.util.*;

public class ArraysTest{

public static void main(String [] args) {

String [] colors = {"blue", "red", "green", "yellow", "orange"};

// It is necessary to have an ordered array

Arrays.sort(colors);

for(String color : colors)

System.out.print(color + " ");

int index1 = Arrays.binarySearch(colors, "orange");

int index2 = Arrays.binarySearch(colors, "violet");

System.out.println("\norange => " + index1);

System.out.println("violet => " + index2);

}

The output is something like this:

blue green orange red yellow
orange => 2
violet => -5

blue green orange red yellow

orange => 2

violet => -5

According to the API:

Parameters:
- a – the array to be searched
- key – the value to be searched for
Returns:
- index of the search key, if it is contained in the array; otherwise, (-(insertion point) – 1). The insertion point is defined as the point at which the key would be inserted into the array: the index of the first element greater than the key, or a.length if all elements in the array are less than the specified key. Note that this guarantees that the return value will be >= 0 if and only if the key is found.
Throws:
- ClassCastException – if the search key is not comparable to the elements of the array.

Explanation

The first result after searching for “orange” is clear because “orange” was found in the index: 2.

Second result is a little more complex. Let me ask you, was “violet” found in the array? what should the index where “violet” be inserted? Well, see next image to understand better:

As you can see index:4 is where “violet” should be inserted. For this reason binarySearch return -5 (see next operation for more details):

-(insertion point) - 1 = -(4) -1 = -5

1	-(insertion point) - 1 = -(4) -1 = -5

That’s it, at this moment.

Be happy with your code!

—

Alex Arriaga

alex-arriaga July 10, 2013

Saving a complex JSON object in a cookie by using jQuery (demo included in PHP)

jQuery, Web Development 8 Replies

Today, I spent almost three hours to test and implement a mechanism to save a complex JSON object and get it to render in a HTML output,, for this reason I would like to explain what was the ~~best~~ easiest way that I found for saving my object.

First, I would recommend you to be sure that your object is well-created, I mean, it is important that your JSON object is according to JavaScript Object Notation (you can visit this link to read more about: http://www.json.org/).

Second, I have used some compatible plugins with jQuery (I have tested this plugins using jQuery 1.8.2, this because in my project jQuery had already existed, also I have tested in jQuery 1.10.2), In a nutshell, we need the next JavaScript files:

Creating our complex JSON object

I have decided to use PHP to create our testing object (because most of developers have knowledge in this programming language).

// An array to simulate a complex JSON object
		$userSettings =  array(
			"personal_information" => array(
				"name" => "Alex",
				"last_name" => "Arriaga"
				),
			"extra_information" => array(
				"twitter" => "alex_arriaga_m",
				"facebook" => "alex.arriaga.m",
				"website" => "http://www.alex-arriaga.com/",
				"programming_languages" => array("HTML5", "CSS3", "JavaScript", "PHP", "Java", "C# .NET", "AWK", "LESS", "XML")
			)
		);

		// Creating the JSON object
		$jsonObject = json_encode($userSettings);

// An array to simulate a complex JSON object

$userSettings = array(

"personal_information" => array(

"name" => "Alex",

"last_name" => "Arriaga"

"extra_information" => array(

"twitter" => "alex_arriaga_m",

"facebook" => "alex.arriaga.m",

"website" => "http://www.alex-arriaga.com/",

"programming_languages" => array("HTML5", "CSS3", "JavaScript", "PHP", "Java", "C# .NET", "AWK", "LESS", "XML")

)

);

// Creating the JSON object

$jsonObject = json_encode($userSettings);

Saving and getting our complex JSON object

Now, we can create a simple JavaScript code to save our JSON object and get it later.

	(function($){
		$(document).on('ready', function(){
			//A cookie by the name 'userSettings' now exists with a serialized copy of $userSettings
			$.cookies.set( 'userSettings', <?php echo $jsonObject; ?> );

			//A variable named 'userSettings' now holds the unserialized object, it should be identical to the PHP variable 'userSettings'
			var userSettings = $.cookies.get( 'userSettings' );

			// Do something with the values read from cookie
			console.log(userSettings);
		});
	})(jQuery);

(function($){

$(document).on('ready', function(){

//A cookie by the name 'userSettings' now exists with a serialized copy of $userSettings

$.cookies.set( 'userSettings', <?php echo $jsonObject; ?> );

//A variable named 'userSettings' now holds the unserialized object, it should be identical to the PHP variable 'userSettings'

var userSettings = $.cookies.get( 'userSettings' );

// Do something with the values read from cookie

console.log(userSettings);

});

})(jQuery);

Verifying result

To see the saved object please use Firebug (in cookie tab). See next images like a demo of this.

Figure 1. Saving JSON object

Figure 2. Getting JSON object and verifying in Firebug console

It is possible to configure several parameters, but I think is better for you read them in the official github page of this plugin: https://code.google.com/p/cookies/

You can download this example code for testing more parameters or personalize according to your project. Download here.

That’s it. Be happy with your code!

—

Alex Arriaga

alex-arriaga July 10, 2013

How to trim or delete trailing white spaces automatically on save in Sublime Text 2

Mac OSX, Operating Systems, Web Development No Reply

Sublime Text 2 is my opinion one of most beautiful and useful editors for web developers, of course I really like Notepad++ (but this one, it doesn’t have a version for MAC OSX). A common task when we are creating awesome source codes is trim/delete trailing white spaces, because these are not good and even they could bring on some issues in programming. So, if you want to do this automatically when you save your files and you are using Sublime Text 2, then is really easy, please just:

1) Click on: Sublime Text 2 > Preferences > Settings – User

2) This will open a file with a JSON format configuration.

3) Add the next configuration parameter to your Sublime Text 2:

"trim_trailing_white_space_on_save" : true

1	"trim_trailing_white_space_on_save" : true

In my case my configuration file looks like this:

{
	"color_scheme": "Packages/Color Scheme - Default/Eiffel.tmTheme",
	"font_size": 14.0,
	"ignored_packages":
	[
		"Vintage"
	],
	"trim_trailing_white_space_on_save" : true
}

{

"color_scheme": "Packages/Color Scheme - Default/Eiffel.tmTheme",

"font_size": 14.0,

"ignored_packages":

[

"Vintage"

"trim_trailing_white_space_on_save" : true

}

Note: It is important the comma “,” before the line “trim_trailing_white_space_on_save” : true in order to avoid error in your configuration file.

For Windows users

I think, Sublime Text 2 – Windows version has an alike option, please look for this and follow the same procedure.

That’s it. Be happy with your code!

—

Alex Arriaga

alex-arriaga July 10, 2013

How to find blank lines in a set of files in GNU/Linux or UNIX-Like Operating Systems

GNU/Linux, Mac OSX, Operating Systems No Reply

This short script could help you find blank lines at the beginning or the end of a set of files (in this case in the same directory where you run this script).

for f in `find . -type f`; do 
  for t in head tail; do 
    $t -1 $f  |egrep '^[  ]*$' >/dev/null && echo "blank line at the $t of $f"; 
  done; 
done

for f in `find . -type f`; do

for t in head tail; do

$t -1 $f |egrep '^[ ]*$' >/dev/null && echo "blank line at the $t of $f";

done;

done

To run this command:

1) Open your terminal (en GNU/Linux or UNIX-Like OS, it doesn’t work in any Microsoft Windows OS).

2) You can copy and paste the command or if you prefer put it in a single line, go ahead the command also will work!

for f in `find . -type f`; do for t in head tail; do $t -1 $f  |egrep '^[  ]*$' >/dev/null && echo "blank line at the $t of $f"; done; done

1	for f in `find . -type f`; do for t in head tail; do $t -1 $f \|egrep '^[ ]*$' >/dev/null && echo "blank line at the $t of $f"; done; done

Thanks to the original post in stackoverflow: http://stackoverflow.com/questions/1943727/find-all-files-with-blank-or-ws-at-bof-or-eof

That’s it. Be happy with your code!

—

Alex Arriaga

alex-arriaga July 10, 2013

How to solve the “Cannot modify header information – headers already sent by…” error in your PHP applications

CakePHP, Web Development No Reply

Today, when I updated a repository in git I realized that my co-workers -accidentally- broke a project (in CakePHP). What error was displaying? simple and a little confusing:

Warning (2): Cannot modify header information - headers already sent by (output started at /app/config/database.php:1) [CORE/cake/libs/controller/controller.php, line 742]

1	Warning (2): Cannot modify header information - headers already sent by (output started at /app/config/database.php:1) [CORE/cake/libs/controller/controller.php, line 742]

So, for solving this common PHP issue, I recommend use these steps:

1) The first thing is to find a file (or several files) with a blank line at the beginning or at the end of the file. You can read this article for finding a list of files by using a short command: How to find blank lines in a set of files in GNU/Linux or UNIX-Like Operating Systems

2) Be sure that your “pure” PHP files don’t contain a white space or a blank line after CLOSING PHP TAG (?>) or before STARTING PHP TAG (<?php ). In fact, when you create a PHP file (with only PHP source code) it is NOT recommended to use CLOSING PHP TAG (?>). You can read about this in: http://framework.zend.com/manual/1.12/en/coding-standard.php-file-formatting.html (thanks to Daniel Guerrero for sending this link).

3) As you can see -in my case- the error was indicating that the issue was related with a file called database.php in line:1. So, I looked for a blank line or white spaces but no, the file did not have any of these 🙁

4) Last thing that you need to know is about ENCODING, yes when you create or modify a file, some editors save your files in a specific encondig, please read a little more in these links:

When previous steps don’t work, try to find what is the character-encoding used by your PHP file, usually they are in ANSI, or UTF-8 (this second encoding is recommended). So, in my case only was necessary to change the character-encoding to UTF-8 and that solved the problem.

That’s it. Be happy with your project 🙂

—

Alex Arriaga

alex-arriaga June 28, 2013

The easiest way to check if an element exists with jQuery

jQuery, Web Development 1 Reply

When you need to know if an element exists in the DOM (Document Object Model), only uses this small code:

<script type="text/javascript">
(function($){
	$(document).on('ready', function(){
		if( $("element").length ){
			// Do something :)
		}
	});
})(jQuery);	
</script>

(function($){

$(document).on('ready', function(){

if( $("element").length ){

// Do something :)

}

});

})(jQuery);

</script>

The length property returns the number of elements that match with our selector. For example, imagine that you have the next HTML estructure:

<div class="parent">
	<ul>
		<li><a href="#">Some link</a></li>
	</ul>
	<div class="child"></div>
</div>

<ul>

</ul>

</div>

If you want to know if the element with class=”child” exists, just it is necessary to do:

<script type="text/javascript">
(function($){
	$(document).on('ready', function(){
		if( $(".child").length ){
			alert("Child exists");
		}
	});
})(jQuery);	
</script>

(function($){

$(document).on('ready', function(){

if( $(".child").length ){

alert("Child exists");

}

});

})(jQuery);

</script>

That’s all at this moment, be happy with your code!

—

Alex Arriaga

alex-arriaga June 24, 2013

Installing PHP Composer on Mac OS X and how to solve detect_unicode error

PHP, Web Development 2 Replies

The easiest way that I have found to install PHP Composer is following next commands:

1) Go to your directory where you want to install PHP Composer, for example I want to install PHP Composer in the next directory (this will allow install Laravel Framework, but the same applies for any other purpose).

cd /Applications/XAMPP/htdocs/laravel

1	cd /Applications/XAMPP/htdocs/laravel

2) Try to install PHP composer executing the next line:

curl -s http://getcomposer.org/installer | php

1	curl -s http://getcomposer.org/installer \| php

Now, if when you execute this command an error like this appears (take it easy, we can solve it, jejeje):

#!/usr/bin/env php
Some settings on your machine make Composer unable to work properly.
Make sure that you fix the issues listed below and run this script again:

The detect_unicode setting must be disabled.
Add the following to the end of your `php.ini`:
    detect_unicode = Off

A php.ini file does not exist. You will have to create one.
If you can not modify the ini file, you can also run `php -d option=value` to modify ini values on the fly. You can use -d multiple times.

#!/usr/bin/env php

Some settings on your machine make Composer unable to work properly.

Make sure that you fix the issues listed below and run this script again:

The detect_unicode setting must be disabled.

Add the following to the end of your `php.ini`:

detect_unicode = Off

A php.ini file does not exist. You will have to create one.

If you can not modify the ini file, you can also run `php -d option=value` to modify ini values on the fly. You can use -d multiple times.

3) In order to solve the detect_unicode error, please just add a parameter to your command as the next line shows:

curl -s getcomposer.org/installer | php -d detect_unicode=Off

1	curl -s getcomposer.org/installer \| php -d detect_unicode=Off

4) That’s it! Now, be happy with a message like this:

All settings correct for using Composer
Downloading...

Composer successfully installed to: /Applications/XAMPP/xamppfiles/htdocs/laravel/composer.phar
Use it: php composer.phar

All settings correct for using Composer

Downloading...

Composer successfully installed to: /Applications/XAMPP/xamppfiles/htdocs/laravel/composer.phar

Use it: php composer.phar

See you the next time, my friend!

—

Alex Arriaga

alex-arriaga June 23, 2013

Session 8: Tutorial in video HTML5 + CSS2 and CSS3 (in spanish)

CSS3, HTML5, Web Development 1 Reply

Hi my friends!

Here is the eighth and last session of HTML5, CSS2 and CSS3.

Enjoy and learn!

alex-arriaga June 23, 2013

Session 7: Tutorial in video HTML5 + CSS2 and CSS3 (in spanish)

CSS3, HTML5, Web Development 1 Reply

Hi my friends!

Here is the seventh session of HTML5, CSS2 and CSS3.

Enjoy and learn!

What would you like to know about?

Alex Arriaga

All posts by
alex-arriaga

How to use and understand Binary Search on Java SE

Saving a complex JSON object in a cookie by using jQuery (demo included in PHP)

How to trim or delete trailing white spaces automatically on save in Sublime Text 2

How to find blank lines in a set of files in GNU/Linux or UNIX-Like Operating Systems

How to solve the “Cannot modify header information – headers already sent by…” error in your PHP applications

The easiest way to check if an element exists with jQuery

Installing PHP Composer on Mac OS X and how to solve detect_unicode error

Session 8: Tutorial in video HTML5 + CSS2 and CSS3 (in spanish)

Session 7: Tutorial in video HTML5 + CSS2 and CSS3 (in spanish)

Join me, have fun and learn!

Recent Posts

Recent Comments

Join me, have fun and learn!

Recent Posts

Day quote…

Recent Comments

Categories

Archives

Join me, have fun and learn!

Recent Posts

Archives

Recent Comments

Categories

What would you like to know about?

All posts by alex-arriaga

Join me, have fun and learn!

Tag Cloud

Recent Posts

Recent Comments

Join me, have fun and learn!

Recent Posts

Day quote…

Recent Comments

Categories

Tag Cloud

Archives

Join me, have fun and learn!

Recent Posts

Archives

Tag Cloud

Recent Comments

Categories

All posts by
alex-arriaga