Java Swing Tips

In a java swing application, if you have added some new component at runtime, you can make it appear on the containers just by using the function validate();

Also, it is always better to use the JTextArea component with a JScrollPane.

Java classpath setting on UNIX/LINUX

Just a caveat:-

On Windows :-

java -cp path1;path2 abc

On Linux:-

the colon ':' separates the paths instead of the  semicolon ';'

java -cp path1:path2 abc

Some common tech jargon:-

Hello,

What I am about to discuss are very trivial technical points for programmers, But just for the sake of Jargons :-

1) Off-by-one error (OBOE): suppose you want to traverse an array from beginning to end. lets say its size is  100. And in the implementation programming language, the index starts from zero.

The following code segment demonstrates OBOE:-

for(i=0;i<=100;i++)

{

----------------------- some code

}

We end up traversing 101 elements. the array ranges from o to 99.

Its very common in C language.

2) Fencepost Error:-

This is an error associated while answering questions such as:-

If you build a straight fence 100m long with posts 10m apart, how many posts do you need?

At first sight we would say:- 100/10 = 10 posts are needed.

But looking closely we find that the answer is ((total_length/individual_length)+1) posts are needed.

See you guys,

Bye

REASONS FOR: java.net.SocketException: Permission denied: connect

Hello friends,

Was trying to fetch response from a website, through the use of Socket class in a Java program.

Socket s1=new Socket("www.oracle.com",80);

Was getting the error:-

java.net.SocketException: Permission denied: connect

Solution:

The most probable reason for this, is that we are trying to access a port which is below 1023, which requires special privileges. In my case, I did not login as the administrator. Hence the error.

If I run the same lines of code , logged in as administrator, there will be no error.

Hope it helps,

Ashish Mishra

Struts CheckBox BUG

Hi friends,

Today I learnt about a bug in struts version 1.2

The checkbox bug :- Its quite famous among struts framework related programmers :-

The bug is that

if you uncheck a checkbox and submit a form, then the corresponding field in the targeted bean (the one in which form elements will be filled) will not be altered and hence, the next time you try to get back the data, you will have the discrepancy of a checked check-box (you will get it checked when you were expecting it to be unchecked).

This is due to the fact that, internally struts 1.2 has a setter method only if the checkbox is checked and not when its unchecked.

Googling about this may help resolve your additional doubts.

Hi guys,

               Today I had the opportunity of sitting in amdocs fresher's walkin.

The test was conducted online :- It had the following condition:-

1) aptitude test : 20 questions 25 min

2) attention to details :20 questions 25 min

3)  passage - emphasis on attention to detail

4) Core java questions 20 questions

5) SQL - tricky 20 questions

6) Unix. 20 questions