This should do the trick. If the screen doesn’t go then try restarting your PC for the changes to take effect.

“no unique maximal instance exists for type variable U with upper bounds U”

The weird thing was that the file compiled just fine in eclipse!

On further probing I realized it’s a javac bug (check the bug here)

Here’s the workaround -

Bug Scenario :

public class SomeObject {

<U extends SomeObject> U foo1() throws Exception {

SomeObject obj = new SomeObject();
return obj.foo1();
}

}

Solve this way :

public class SomeObject {

<U extends SomeObject> U foo1() throws Exception {

SomeObject obj = new SomeObject();
return obj.<U>foo1();
}
}

substring(start, stop) :

start (mandatory) – The starting index

stop (optional) – The index to stop extraction

Example: If you want to find the first 3 alphabets in the word INDIA, the code would be

var name = “INDIA”;

var firstThreeLetters = name.substring(0,3);

alert(firstThreeLetters);

The alert would display : IND

Note: Here start is 0 hence the extraction starts from the letter in the 0th position i.e. the first letter. The stop index is 3 which means extraction would stop at index 3 (the letter at index 3 will not be extracted)

Since stop is optional, if you only specify the start parameter, all the letters after the starting index (including the one at the start) would be extracted.

Example: Consider the same example as above, for the word INDIA if we were to give the start as 1

var name = “INDIA”;

var extractedLetters = name.substring(1);

alert(extractedLetters);

The alert would display NDIA as the output of the javascript substring method.

————————————————————————————

Indepth Analysis of Javascript substring

Let’s try and create our own Javascript substring function.

String.prototype.mySubstring = function(start,stop) {

var charArray = this.split(’);

var temp = “”;

for(var i=start;<stop;i++)

{

temp = temp + charArray[i];

}

return temp;

}

Now, you can use this function instead of the default substring function. Include the above code in any page and you can use mySubstring inside any javascript function.

Example:

var name = “INDIA”;

var extractedLetters = name.mySubstring(0,3);

alert(extractedLetters);

The alert would display IND thus emulating the real Javascript substring function!

Note: This method is just a food for thought. To help you understand how exactly such methods would be implemented. For all practical purposes use the default substring function of Javascript.

Right Click on your desktop and select

New -> Shortcut.

A shortcut will be created and a dialog box would pop up.

Copy paste %windir%\system32\rundll32.exe user32.dll,LockWorkStation into the text box of the dialog.

Click Next. Type any name you like.

A desktop shortcut with the name that you gave would be created. Double click anytime to lock your computer.

Here’s the code I tried in my first attempt:

<%int i=0;%>

//iteration logic here

<html:text property=”example” styleid=”example<%=i%>”>

Well, if you write the code as shown above, the html code generated would be :

<input type=”text” name=”example” id = “example<%=i%>”>

and not

<input type=”text” name=”example” id=”example0″>

To get the expected result, i.e. for the scriptlet to work inside the struts html tag, write as below:

<html:text property=”example” styleid=’<%=”example”+i%>’

That’s it. If any of you ever find out a way to generate different id’s for html elements with the same name using strtus tags exclusively then do let me know

OVERRIDING – when you extend a class and write a method in the derived class which is exactly similar to the one present in the base class, it is termed as overriding.

Example:

public class BaseClass{

public void methodToOverride()

{

//Some code here

}

}

public class DerivedClass extends BaseClass{

public void methodToOverride()

{

//Some new code here

}

}

As you can see, in the class DerivedClass, we have overridden the method present in the BaseClass with a completely new piece of code in the DerivedClass.

What that effectively means is that if you create an object of DerivedClass and call the methodToOverride() method, the code in the derivedClass will be executed. If you hadn’t overridden the method in the DerivedClass then the method in the BaseClass would have been called.

OVERLOADING -  when you have more than one method with the same name but different arguments, the methods are said to be overloaded.

Example:

public class OverLoadingExample{

public void add(int i, int j)

{

int k = i + j;

}

public void add(String s, String t)

{

int k = Integer.parseInt(s) + Integer.parseInt(t);

}

}

As you can see in the example above, we have the same method add() taking two parameters but with different data types. Due to overloading we can now call the add method by either passing it a String or int

I found that if there’s background=”#” then the page tends to submit the same request twice!! Call it a bug in html… Not sure about that. But the code is as below:

<table background=”#”>

<tr>

<td>

This piece of code in your page will cause the request to be submitted twice!!

</td>

</tr>

</table>

Please leave a comment if you have anything to add to this

navigator.appName

For Ex.

function identifyBrowser()

{

alert(”You seem to be working on the “+navigator.appName+” browser”);

}

The navigator method has a few other properties like:

appCodeName

appVersion

language

mimeTypes[]

platform

plugins[]

userAgent

Click here to view the example

First and foremost, all apologies for such a long delay in writing a new post. I was kind of tied up with some work. But from now on I’ll try my best to be regular

We will be using regular expression for email validation. And don’t you worry. I’ll see to it that by the time you finish reading this post, you would have got a fair idea about Regular Expressions.

Lets try to construct the regular expression that we will be using to check the email entered by the user.

Consider these two email id’s : example@example.com and exam_ple@ex.am.ple

Quick references:

. (dot) matches any single character. Ex. “h.t” will match “hut”, “hot” etc.

[ ] Brackets match a single character that is contained in the given expression. Ex. [a-d] will match ‘a’ or ‘b’ or ‘c’ or ‘d’. Similarly, [a-cx-z] will match ‘a’ or ‘b’ or ‘c’ or ‘x’ or ‘y’ or ‘z’.

^ Matches the starting position within the given string.

$ Matches the ending position of the given string.

* Matches the preceding element zero or more times.

+ Matches the preceding element one or more times.

{n,m} Matches the occurrence of the previous symbol not less than n and not more than m times.

\ Its the escape character. Ex. As shown above, .(dot) matches a single occurrence of any character. But what if we need to match an occurrence of (dot) itself. We write it as \.

Considering the email id’s shown above, we can list our requirements as follows:

1. Email Id needs to start with alphabets or numbers – regex will be ^([a-zA-Z0-9]) i.e. the email id should start with either an alphabet or a number.

2. It can contain any number of alphabets, numbers and a few special characters. RegEx will be ([a-zA-Z0-9\.\_\-])*

3. Then there should be the famous ‘@’ symbol which we simply write as @

4. Then again any number of alphabets or numbers or ‘-’ are allowed. RegEx is (([a-zA-Z0-9\-])+\.)+

5. Finally, the ending of the email ([a-zA-Z]{2,4})+$

Here’s the final regular expression for validating the email id’s :

^([a-zA-Z0-9])([a-zA-Z0-9\.\_\-])*@(([a-zA-Z0-9])+(\.))+([a-zA-Z]{2,4})+$

Now, lets see how to use it in the javascript. We make use of the search() function of javascript.

function emailValidation(){

var emailRegEx = /^([a-zA-Z0-9])([a-zA-Z0-9\._-])*@(([a-zA-Z0-9])+(\.))+([a-zA-Z]{2,4})+$/ ;

var testMail = “example@example.com”;

if(testMail.search(emailRegEx)==-1)

alert(”Invalid”);

}

Click Here to view the example.

UPDATE 1 : Please use the regular expression shown below instead of the one above. This fixes the bug which allowed consecutive special charaters i.e. previously example..example@example.com was displayed as valid. It has been fixed now. Please do test the script before you plan to use it. If you find some problems in it then do let me know. I’ll try and fix it.

var emailRegEx = /^([a-zA-Z0-9])(([a-zA-Z0-9])*([\._-])?([a-zA-Z0-9]))*@(([a-zA-Z0-9\-])+(\.))+([a-zA-Z]{2,4})+$/